@article{pra29,

title = {Testing collapse models with Bose-Einstein-condensate interferometry},

author = {B. Schrinski and P. Haslinger and J. Schmiedmayer and K. Hornberger and S. Nimmrichter},

url = {https://www.klaus-hornberger.de/pdf/pra29.pdf, PDF},

doi = {10.1103/PhysRevA.107.043320},

year  = {2023},

date = {2023-04-24},

journal = {Physical Review A},

volume = {107},

pages = {043320},

abstract = {The model of continuous spontaneous localization (CSL) is the most prominent consistent modification of quantum mechanics predicting an objective quantum-to-classical transition. Here we show that precision interferometry with Bose-Einstein-condensed atoms can serve to lower the current empirical bound on the localization rate parameter by several orders of magnitude. This works by focusing on the atom count distributions rather than just mean population imbalances in the interferometric signal of squeezed Bose-Einstein condendates, without the need for highly entangled Greenberger-Horne-Zeilinger-like states. In fact, the interplay between CSL-induced diffusion and dispersive atom-atom interactions results in an amplified sensitivity of the condensate to CSL. We discuss experimentally realistic measurement schemes utilizing state-of-the-art experimental techniques to test new regions of parameter space and, pushed to the limit, to probe and potentially rule out large relevant parameter regimes of CSL.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{prl19,

title = {Macroscopic Quantum Test with Bulk Acoustic Wave Resonators},

author = {B. Schrinski and Y. Yang and U. L\"{u}pke and M. Bild and Y. Chu and K. Hornberger and S. Nimmrichter and M. Fadel},

url = {https://www.klaus-hornberger.de/pdf/prl19.pdf, PDF 

https://www.klaus-hornberger.de/pdf/prl19_supp.pdf, Supplementary Information 

https://physics.aps.org/articles/v16/s45, Featured in Physics 16 (2023)},

doi = {10.1103/PhysRevLett.130.133604},

year  = {2023},

date = {2023-03-29},

urldate = {2023-03-29},

journal = {Physical Review Letters},

volume = {130},

pages = {133604},

abstract = {Recently, solid-state mechanical resonators have become a platform for demonstrating nonclassical behavior of systems involving a truly macroscopic number of particles. Here, we perform the most macroscopic quantum test in a mechanical resonator to date, which probes the validity of quantum mechanics by ruling out a classical description at the microgram mass scale. This is done by a direct measurement of the Wigner function of a high-overtone bulk acoustic wave resonator mode, monitoring the gradual decay of negativities over tens of microseconds. While the obtained macroscopicity of μ=11.3 is on par with state-of-the-art atom interferometers, future improvements of mode geometry and coherence times could test the quantum superposition principle at unprecedented scales and also place more stringent bounds on spontaneous collapse models.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{qst3,

title = {Research campaign: Macroscopic quantum resonators (MAQRO)},

author = {R. Kaltenbaek and {et al.}},

url = {https://www.klaus-hornberger.de/pdf/qst3.pdf, PDF},

doi = {10.1088/2058-9565/aca3cd},

year  = {2023},

date = {2023-01-05},

urldate = {2023-01-05},

journal = {Quantum Science and Technology},

volume = {8},

pages = {014006},

abstract = {The objective of the proposed macroscopic quantum resonators (MAQRO) mission is to harness space for achieving long free-fall times, extreme vacuum, nano-gravity, and cryogenic temperatures to test the foundations of physics in macroscopic quantum experiments at the interface with gravity. Developing the necessary technologies, achieving the required sensitivities and providing the necessary isolation of macroscopic quantum systems from their environment will lay the path for developing novel quantum sensors. Earlier studies showed that the proposal is feasible but that several critical challenges remain, and key technologies need to be developed. Recent scientific and technological developments since the original proposal of MAQRO promise the potential for achieving additional science objectives. The proposed research campaign aims to advance the state of the art and to perform the first macroscopic quantum experiments in space. Experiments on the ground, in micro-gravity, and in space will drive the proposed research campaign during the current decade to enable the implementation of MAQRO within the subsequent decade.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{prl18,

title = {Force-gradient sensing and entanglement via feedback cooling of interacting nanoparticles},

author = {H. Rudolph and U. Deli\'{c} and M. Aspelmeyer and K. Hornberger and B. A. Stickler},

url = {https://www.klaus-hornberger.de/pdf/prl18.pdf, PDF 

https://www.klaus-hornberger.de/pdf/prl18_supp.pdf, Supplementary Information},

doi = {10.1103/PhysRevLett.129.193602},

year  = {2022},

date = {2022-11-02},

urldate = {2022-11-02},

journal = {Physical Review Letters},

volume = {129},

pages = {193602},

abstract = {We show theoretically that feedback cooling of two levitated, interacting nanoparticles enables differential sensing of forces and the observation of stationary entanglement. The feedback drives the two particles into a stationary, nonthermal state which is susceptible to inhomogeneous force fields and which exhibits entanglement for sufficiently strong interparticle couplings. We predict that force-gradient sensing at the zepto-Newton per micron range is feasible and that entanglement due to the Coulomb interaction between charged particles can be realistically observed in state-of-the-art setups.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{science1,

title = {Tunable light-induced dipole-dipole interaction between optically levitated nanoparticles},

author = {J. Rieser and M. A. Ciampini and H. Rudolph and N. Kiesel and K. Hornberger and B. A. Stickler and M. Aspelmeyer and U. Deli\'{c}},

url = {mailto:klaus.hornberger@uni-due.de, PDF available upon request 

https://www.klaus-hornberger.de/pdf/science1_supp.pdf, Supplementary Information 

https://doi.org/10.1038/d41586-022-02322-6, Featured in Nature 

https://doi.org/10.1126/science.add1374, Featured in Science 

https://physicsworld.com/a/nanoparticles-levitated-by-light-exhibit-non-reciprocal-interactions, Featured in Physics World},

doi = {10.1126/science.abp9941},

year  = {2022},

date = {2022-08-25},

urldate = {2022-08-25},

journal = {Science},

volume = {377},

pages = {987},

abstract = {Arrays of optically trapped nanoparticles have emerged as a platform for the study of complex nonequilibrium phenomena. Analogous to atomic many-body systems, one of the crucial ingredients is the ability to precisely control the interactions between particles. However, the optical interactions studied thus far only provide conservative optical binding forces of limited tunability. In this work, we exploit the phase coherence between the optical fields that drive the light-induced dipole-dipole interaction to couple two nanoparticles. In addition, we effectively switch off the optical interaction and observe electrostatic coupling between charged particles. Our results provide a route to developing fully programmable many-body systems of interacting nanoparticles with tunable nonreciprocal interactions, which are instrumental for exploring entanglement and topological phases in arrays of levitated nanoparticles.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{prxq1,

title = {Surface-induced decoherence and heating of charged particles},

author = {L. Martinetz and K. Hornberger and B. A. Stickler},

url = {https://www.klaus-hornberger.de/pdf/prxq1.pdf, PDF},

doi = {10.1103/PRXQuantum.3.030327},

year  = {2022},

date = {2022-08-24},

journal = {PRX Quantum},

volume = {3},

pages = {030327},

abstract = {Levitating charged particles in ultrahigh vacuum provides a preeminent platform for quantum information processing, for quantum-enhanced force and torque sensing, for probing physics beyond the standard model, and for high-mass tests of the quantum superposition principle. Existing setups, ranging from single atomic ions to ion chains and crystals to charged molecules and nanoparticles, are crucially impacted by fluctuating electric fields emanating from nearby electrodes used to control the motion. In this article, we provide a theoretical toolbox for describing the rotational and translational quantum dynamics of charged nano- to microscale objects near metallic and dielectric surfaces, as characterized by macroscopic dielectric response functions. The resulting quantum master equations describe the coherent surface-particle interaction, due to image charges and Casimir-Polder potentials, as well as surface-induced decoherence and heating, with the experimentally observed frequency and distance scaling. We explicitly evaluate the master equations for relevant setups, thereby providing the framework for describing and mitigating surface-induced decoherence as required in future quantum technological applications.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pra28,

title = {Interferometric control of nanorotor alignment},

author = {B. Schrinski and B. A. Stickler and K. Hornberger},

url = {https://www.klaus-hornberger.de/pdf/pra28.pdf, PDF},

doi = {10.1103/PhysRevA.105.L021502},

year  = {2022},

date = {2022-02-17},

journal = {Physical Review A},

volume = {105},

pages = {L021502},

abstract = {The intrinsically nonlinear rotation dynamics of rigid bodies offer unprecedented ways to exploit their quantum motion. In this Letter, we devise a rotational analog of Mach-Zehnder interferometry, which allows steering symmetric rotors from fully aligned to completely antialigned. The scheme uses a superposition of four distinct orientations, emerging at the eighth of the quantum revival time, whose interference can be controlled by a weak laser pulse. We develop a semiclassical model of the effect and demonstrate that it persists even in presence of imperfections and decoherence.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{njp6,

title = {Electric trapping and circuit cooling of charged nanorotors},

author = {L. Martinetz and K. Hornberger and B. A. Stickler},

url = {https://www.klaus-hornberger.de/pdf/njp6.pdf, PDF},

doi = {10.1088/1367-2630/ac1c82},

year  = {2021},

date = {2021-09-02},

journal = {New Journal of Physics},

volume = {23},

pages = {093001},

abstract = {The motion of charged particles can be interfaced with electric circuitry via the current induced in nearby pick-up electrodes. Here we show how the rotational and translational dynamics of levitated objects with arbitrary charge distributions can be coupled to a circuit and how the latter acts back on the particle motion. The ensuing cooling rates in series and parallel RLC circuits are determined, demonstrating that quadrupole ion traps are well suited for implementing all-electric cooling. We derive the effective macromotion potential for general trap geometries and illustrate how consecutive rotational and translational resistive cooling of a microscale particle can be achieved in linear Paul traps.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{natrevp1,

title = {Quantum rotations of nanoparticles},

author = {B. A. Stickler and K. Hornberger and M. S. Kim},

url = {mailto:klaus.hornberger@uni-due.de, PDF available upon request},

doi = {10.1038/s42254-021-00335-0},

year  = {2021},

date = {2021-06-29},

urldate = {2021-06-29},

journal = {Nature Reviews Physics},

volume = {3},

pages = {589-597},

abstract = {Rotations of microscale rigid bodies exhibit pronounced quantum phenomena that do not exist for their centre-of-mass motion. By levitating nanoparticles in ultra-high vacuum, researchers are developing a promising platform for observing and exploiting these quantum effects in an unexplored mass and size regime. Recent experimental and theoretical breakthroughs demonstrate exquisite control of nanoscale rotations, setting the stage for the first tabletop tests of rotational superpositions and for the next generation of ultra-precise torque sensors. Here, we review the experimental state of the art and discuss promising routes towards quantum rotations.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{prl17,

title = {Cooling nanorotors by elliptic coherent scattering},

author = {J. Sch\"{a}fer and H. Rudolph and K. Hornberger and A. Stickler},

url = {https://www.klaus-hornberger.de/pdf/prl17.pdf, PDF 

 https://www.klaus-hornberger.de/pdf/pra27.pdf, See also accompanying PRA article},

doi = {10.1103/PhysRevLett.126.163603},

year  = {2021},

date = {2021-04-23},

journal = {Physical Review Letters},

volume = {126},

pages = {163603},

abstract = {Simultaneously cooling the rotational and translational motion of nanoscale dielectrics into the quantum regime is an open task of great importance for sensing applications and quantum superposition tests. Here, we show that the six-dimensional ground state can be reached by coherent-scattering cooling with an elliptically polarized and shaped optical tweezer. We determine the cooling rates and steady-state occupations in a realistic setup and discuss applications for mechanical sensing and fundamental experiments.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pra27,

title = {Theory of nanoparticle cooling by elliptic coherent scattering},

author = {H. Rudolph and J. Sch\"{a}fer and B. A. Stickler and K. Hornberger},

url = {https://www.klaus-hornberger.de/pdf/pra27.pdf, PDF},

doi = {10.1103/PhysRevA.103.043514},

year  = {2021},

date = {2021-04-23},

journal = {Physical Review A},

volume = {103},

pages = {043514},

abstract = {Coherent scattering of an elliptically polarized tweezer into a cavity mode provides a promising platform for cooling levitated nanoparticles into their combined rotational and translational quantum regime [J. Sch\"{a}fer, H. Rudolph, K. Hornberger, and B. A. Stickler, Phys. Rev. Lett. 126, 163603 (2021)]. This article presents the theory of how aspherical nanoparticles are affected by elliptically polarized laser beams, how two orthogonal cavity modes enable rotational and translational cooling, and how the resulting power spectra contain signatures of rotational nonlinearities. We provide analytic expressions for the resulting trapping frequencies, optomechanical coupling strengths, cooling rates, and steady-state occupations, and we study their dependence on the tweezer ellipticity.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{npjqi1,

title = {Quantum electromechanics with levitated nanoparticles},

author = {L. Martinetz and K. Hornberger and J. Millen and M. S. Kim and B. A. Stickler},

url = {https://www.klaus-hornberger.de/pdf/npjqi1.pdf, PDF 

https://www.klaus-hornberger.de/pdf/npjqi1_supp.pdf, Supplementary Information},

doi = {10.1038/s41534-020-00333-7},

year  = {2020},

date = {2020-12-11},

urldate = {2020-12-11},

journal = {npj Quantum Information},

volume = {6},

pages = {101},

abstract = {Preparing and observing quantum states of nanoscale particles is a challenging task with great relevance for quantum technologies and tests of fundamental physics. In contrast to atomic systems with discrete transitions, nanoparticles exhibit a practically continuous absorption spectrum and thus their quantum dynamics cannot be easily manipulated. Here, we demonstrate that charged nanoscale dielectrics can be artificially endowed with a discrete level structure by coherently interfacing their rotational and translational motion with a superconducting qubit. We propose a pulsed scheme for the generation and read-out of motional quantum superpositions and entanglement between several levitated nanoparticles, providing an all-electric platform for networked hybrid quantum devices.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{prl16,

title = {Bragg diffraction of large organic molecules},

author = {C. Brand and F. Kia\lka and S. Troyer and C. Knobloch and K. Simonovi\'{c} and B. A. Stickler},

url = {https://www.klaus-hornberger.de/pdf/prl16.pdf, PDF 

https://www.klaus-hornberger.de/pdf/prl16_supp.pdf, Supplementary Information 

 https://physics.aps.org/articles/v13/s93, Featured in Physics 13 (2020)},

doi = {10.1103/PhysRevLett.125.033604},

year  = {2020},

date = {2020-07-16},

urldate = {2020-07-16},

journal = {Physical Review Letters},

volume = {125},

pages = {033604},

abstract = {We demonstrate Bragg diffraction of the antibiotic ciprofloxacin and the dye molecule phthalocyanine at a thick optical grating. The observed patterns show a single dominant diffraction order with the expected dependence on the incidence angle as well as oscillating population transfer between the undiffracted and diffracted beams. We achieve an equal-amplitude splitting of 14ℏk (photon momenta) and maximum momentum transfer of 18ℏk. This paves the way for efficient, large-momentum beam splitters and mirrors for hot and complex molecules.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{prr2,

title = {Quantum-classical hypothesis tests in macroscopic matter-wave interferometry},

author = {B. Schrinski and S. Nimmrichter and K. Hornberger},

url = {https://www.klaus-hornberger.de/pdf/prr2.pdf, PDF},

doi = {10.1103/PhysRevResearch.2.033034},

year  = {2020},

date = {2020-07-08},

journal = {Physical Review Research},

volume = {2},

pages = {033034},

abstract = {We assess the most macroscopic matter-wave experiments to date as to the extent to which they probe the quantum-classical boundary by demonstrating interference of heavy molecules and cold atomic ensembles. To this end, we consider a rigorous Bayesian test protocol for a parametrized set of hypothetical modifications of quantum theory, including well-studied spontaneous collapse models, that destroy superpositions and reinstate macrorealism. The range of modification parameters ruled out by the measurement events quantifies the macroscopicity of a quantum experiment, while the shape of the posterior distribution resulting from the Bayesian update reveals how conclusive the data are at testing macrorealism. This protocol may serve as a guide for the design of future matter-wave experiments ever closer to truly macroscopic scales.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{prr1,

title = {Orbital angular momentum interference of trapped matter waves},

author = {F. Kia\lka and B. A. Stickler and K. Hornberger},

url = {https://www.klaus-hornberger.de/pdf/prr1.pdf, PDF},

doi = {10.1103/PhysRevResearch.2.022030},

year  = {2020},

date = {2020-05-06},

journal = {Physical Review Research},

volume = {2},

pages = {022030(R)},

abstract = {We introduce a matter wave interference scheme based on the quantization of orbital angular momentum in a ring trap. It operates without beam splitters, is sensitive to geometric phases induced by external gauge fields, and allows measuring interatomic scattering lengths. We argue that orbital angular momentum interferometry offers a versatile platform for quantum coherent experiments with cold atoms and Bose-Einstein condensates using state-of-the-art technology.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pra26,

title = {Entangling levitated nanoparticles by coherent scattering},

author = {H. Rudolph and K. Hornberger and B. A. Stickler},

url = {https://www.klaus-hornberger.de/pdf/pra26.pdf, PDF},

doi = {10.1103/PhysRevA.101.011804},

year  = {2020},

date = {2020-01-29},

journal = {Physical Review A},

volume = {101},

pages = {011804(R)},

abstract = {We show how entanglement between two optically levitated nanoparticles can be generated and detected by coherent scattering of tweezer photons into a single cavity mode. Triggered by the detection of a Stokes photon, the tweezer detuning is switched from the blue to the red; entanglement is then verified by the conditioned anti-Stokes photon flux, which oscillates with the mechanical beat frequency. The proposed setup is realizable with near-future technology and opens the door to experimental observation of nonclassical center-of-mass correlations between two or more levitated nanoscale objects.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pra25,

title = {Macroscopicity of quantum mechanical superposition tests via hypothesis falsification},

author = {B. Schrinski and S. Nimmrichter and B. A. Stickler and K. Hornberger},

url = {https://www.klaus-hornberger.de/pdf/pra25.pdf, PDF},

doi = {10.1103/PhysRevA.100.032111},

year  = {2019},

date = {2019-09-16},

journal = {Physical Review A},

volume = {100},

pages = {032111},

abstract = {We establish an objective scheme to determine the macroscopicity of quantum superposition tests with mechanical degrees of freedom. It is based on the Bayesian hypothesis falsification of a class of macrorealist modifications of quantum theory, such as the model of continuous spontaneous localization. The measure uses the raw data gathered in an experiment, taking into account all measurement uncertainties, and can be used to directly assess any conceivable quantum mechanical test. We determine the resulting macroscopicity for three recent tests of quantum physics: double-well interference of Bose-Einstein condensates, Leggett-Garg tests with atomic random walks, and entanglement generation and read-out of nanomechanical oscillators.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pra24,

title = {Decoherence of non-relativistic bosonic quantum fields},

author = {M. Bola\~{n}os and B. A. Stickler and K. Hornberger},

url = {https://www.klaus-hornberger.de/pdf/pra24.pdf, PDF},

doi = {10.1103/PhysRevA.99.060103},

year  = {2019},

date = {2019-06-27},

journal = {Physical Review A},

volume = {99},

pages = {060103(R)},

abstract = {We present a generic Markovian master equation inducing the gradual decoherence of a bosonic quantum field. It leads to the decay of quantum superpositions of field configurations, while leaving the Ehrenfest equations for both the field and the mode-variables invariant. We characterize the decoherence dynamics analytically and numerically, and show that the semiclassical field dynamics is described by a linear Boltzmann equation in the functional phase space of field configurations.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{qst2,

title = {Levitated electromechanics: all-electrical cooling of charged nano- and micro-particles},

author = {D. Goldwater and B. A. Stickler and L. Martinetz and T. Northup and K. Hornberger and J. Millen},

url = {https://www.klaus-hornberger.de/pdf/qst2.pdf, PDF 

https://www.klaus-hornberger.de/pdf/qst2_supp.pdf, Supplementary Information},

doi = {10.1088/2058-9565/aaf5f3},

year  = {2019},

date = {2019-01-22},

urldate = {2019-01-22},

journal = {Quantum Science and Technology},

volume = {4},

pages = {024003},

abstract = {We show how charged levitated nano- and micro-particles can be cooled by interfacing them with an RLC circuit. All-electrical levitation and cooling is applicable to a wide range of particle sizes and materials, and will enable state-of-the-art force sensing within an electrically networked system. Exploring the cooling limits in the presence of realistic noise we find that the quantum regime of particle motion can be reached in cryogenic environments both for passive resistive cooling and for an active feedback scheme, paving the way to levitated quantum electromechanics.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{physscr1,

title = {Concepts for long-baseline high-mass matter-wave interferometry},

author = {F. Kia\lka and B. A. Stickler and K. Hornberger and Y. Fein and P. Geyer and L. Mairhofer and S. Gerlich and M. Arndt},

url = {https://www.klaus-hornberger.de/pdf/physscr1.pdf, PDF},

doi = {10.1088/1402-4896/aaf243},

year  = {2019},

date = {2019-01-19},

journal = {Physica Scripta},

volume = {94},

pages = {034001},

abstract = {Designing experiments which delocalize ever more complex and more massive particles requires a quantitative assessment of new interferometer configurations. Here, we introduce a figure of merit which quantifies the difference between a genuine quantum interference pattern and a classical shadow and use it to compare a number of near-field interferometer schemes. This allows us to identify the most promising setups for future tests of the quantum superposition principle, and to discuss the perspectives of interferometry with complex molecules and clusters.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{prl15,

title = {Rotational Alignment Decay and Decoherence of Molecular Superrotors},

author = {B. A. Stickler and F. T. Ghahramani and K. Hornberger},

url = {https://www.klaus-hornberger.de/pdf/prl15.pdf, PDF 

https://www.klaus-hornberger.de/pdf/prl15_supp.pdf, Supplementary Information},

doi = {10.1103/PhysRevLett.121.243402},

year  = {2018},

date = {2018-12-14},

urldate = {2018-12-14},

journal = {Physical Review Letters},

volume = {121},

pages = {243402},

abstract = {We present the quantum master equation describing the coherent and incoherent dynamics of a rapidly rotating molecule in the presence of a thermal background gas. The master equation relates the rate of rotational alignment decay and decoherence to the microscopic scattering amplitudes, which we calculate for anisotropic van der Waals scattering. For large rotational energies, we find quantitative agreement of the resulting alignment decay rate with recent superrotor experiments.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{njp5,

title = {Probing macroscopic quantum superpositions with nanorotors},

author = {B. A. Stickler and B. Papendell and S. Kuhn and B. Schrinski and J. Millen and M. Arndt and K. Hornberger},

url = {https://www.klaus-hornberger.de/pdf/njp5.pdf, PDF},

doi = {10.1088/1367-2630/aaece4},

year  = {2018},

date = {2018-12-05},

journal = {New Journal of Physics},

volume = {20},

pages = {122001},

abstract = {Whether quantum physics is universally valid is an open question with far-reaching implications. Intense research is therefore invested into testing the quantum superposition principle with ever heavier and more complex objects. Here we propose a radically new, experimentally viable route towards studies at the quantum-to-classical borderline by probing the orientational quantum revivals of a nanoscale rigid rotor. The proposed interference experiment testifies a macroscopic superposition of all possible orientations. It requires no diffraction grating, uses only a single levitated particle, and works with moderate motional temperatures under realistic environmental conditions. The first exploitation of quantum rotations of a massive object opens the door to new tests of quantum physics with submicron particles and to quantum gyroscopic torque sensors, holding the potential to improve state-of-the-art devices by many orders of magnitude.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{prl14,

title = {Conformer-selection by matter-wave interference},

author = {C. Brand and B. A. Stickler and C. Knobloch and A. Shayeghi and K. Hornberger and M. Arndt},

url = {https://www.klaus-hornberger.de/pdf/prl14.pdf, PDF 

https://www.klaus-hornberger.de/pdf/prl14_supp.pdf, Supplementary Information},

doi = {10.1103/PhysRevLett.121.173002},

year  = {2018},

date = {2018-10-23},

urldate = {2018-10-23},

journal = {Physical Review Letters},

volume = {121},

pages = {173002},

abstract = {We establish that matter-wave diffraction at near-resonant ultraviolet optical gratings can be used to spatially separate individual conformers of complex molecules. Our calculations show that the conformational purity of the prepared beam can be close to 100% and that all molecules remain in their electronic ground state. The proposed technique is independent of the dipole moment and the spin of the molecule and thus paves the way for structure-sensitive experiments with hydrocarbons and biomolecules, such as neurotransmitters and hormones, which have evaded conformer-pure isolation so far.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{prl13,

title = {Rotational friction and diffusion of quantum rotors},

author = {B. A. Stickler and B. Schrinski and K. Hornberger},

url = {https://www.klaus-hornberger.de/pdf/prl13.pdf, PDF 

https://www.klaus-hornberger.de/pdf/prl13_supp.pdf, Supplementary Information},

doi = {10.1103/PhysRevLett.121.040401},

year  = {2018},

date = {2018-07-23},

urldate = {2018-07-23},

journal = {Physical Review Letters},

volume = {121},

pages = {040401},

abstract = {We present the Markovian quantum master equation describing rotational decoherence, friction, diffusion, and thermalization of planar, linear, and asymmetric rotors in contact with a thermal environment. It describes how an arbitrary initial rotation state decoheres and evolves toward a Gibbs-like thermal ensemble, as we illustrate numerically for the linear and the planar top, and it yields the expected rotational Fokker-Planck equation of Brownian motion in the semiclassical limit.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pre2,

title = {Gas-induced friction and diffusion of rigid rotors},

author = {L. Martinetz and K. Hornberger and B. A. Stickler},

url = {https://www.klaus-hornberger.de/pdf/pre2.pdf, PDF 

https://www.klaus-hornberger.de/pdf/pre2_erratum.pdf, Erratum},

doi = {10.1103/PhysRevE.97.052112},

year  = {2018},

date = {2018-05-11},

urldate = {2018-05-11},

journal = {Physical Review E},

volume = {97},

pages = {052112},

abstract = {We derive the Boltzmann equation for the rotranslational dynamics of an arbitrary convex rigid body in a rarefied gas. It yields as a limiting case the Fokker-Planck equation accounting for friction, diffusion, and nonconservative drift forces and torques. We provide the rotranslational friction and diffusion tensors for specular and diffuse reflection off particles with spherical, cylindrical, and cuboidal shape, and show that the theory describes thermalization, photophoresis, and the inverse Magnus effect in the free molecular regime.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{njp4,

title = {Quantum angular momentum diffusion of rigid bodies},

author = {B. Papendell and B. A. Stickler and K. Hornberger},

url = {https://www.klaus-hornberger.de/pdf/njp4.pdf, PDF},

doi = {10.1088/1367-2630/aa99d1},

year  = {2017},

date = {2017-12-07},

journal = {New Journal of Physics},

volume = {19},

pages = {122001},

abstract = {We show how to describe the diffusion of the quantized angular momentum vector of an arbitrarily shaped rigid rotor as induced by its collisional interaction with an environment. We present the general form of the Lindblad-type master equation and relate it to the orientational decoherence of an asymmetric nanoparticle in the limit of small anisotropies. The corresponding diffusion coefficients are derived for gas particles scattering off large molecules and for ambient photons scattering off dielectric particles, using the elastic scattering amplitudes.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{natcom4,

title = {Optically driven ultra-stable nanomechanical rotor},

author = {S. Kuhn and B. A. Stickler and A. Kosloff and F. Patolsky and K. Hornberger and M. Arndt and J. Millen},

url = {https://www.klaus-hornberger.de/pdf/natcom4.pdf, PDF},

doi = {10.1038/s41467-017-01902-9},

year  = {2017},

date = {2017-11-21},

journal = {Nature Communications},

volume = {8},

pages = {1670},

abstract = {Nanomechanical devices have attracted the interest of a growing interdisciplinary research community, since they can be used as highly sensitive transducers for various physical quantities. Exquisite control over these systems facilitates experiments on the foundations of physics. Here, we demonstrate that an optically trapped silicon nanorod, set into rotation at MHz frequencies, can be locked to an external clock, transducing the properties of the time standard to the rod's motion with a remarkable frequency stability fr/Δfr of 7.7×1011. While the dynamics of this periodically driven rotor generally can be chaotic, we derive and verify that stable limit cycles exist over a surprisingly wide parameter range. This robustness should enable, in principle, measurements of external torques with sensitivities better than 0.25 zNm, even at room temperature. We show that in a dilute gas, real-time phase measurements on the locked nanorod transduce pressure values with a sensitivity of 0.3%},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{qst1,

title = {Sensing spontaneous collapse and decoherence with interfering Bose-Einstein condensates},

author = {B. Schrinski and K. Hornberger and S. Nimmrichter},

url = {https://www.klaus-hornberger.de/pdf/qst1.pdf, PDF},

doi = {10.1088/2058-9565/aa8682},

year  = {2017},

date = {2017-09-07},

journal = {Quantum Science and Technology},

volume = {2},

pages = {044010},

abstract = {We study how matter-wave interferometry with Bose-Einstein condensates is affected by hypothetical collapse models and by environmental decoherence processes. Motivated by recent atom fountain experiments with macroscopic arm separations, we focus on the observable signatures of first-order and higher-order coherence for different two-mode superposition states, and on their scaling with particle number. This can be used not only to assess the impact of environmental decoherence on many-body coherence, but also to quantify the extent to which macrorealistic collapse models are ruled out by such experiments. We find that interference fringes of phase-coherently split condensates are most strongly affected by decoherence, whereas the quantum signatures of independent interfering condensates are more immune against macrorealistic collapse. A many-body enhanced decoherence effect beyond the level of a single atom can be probed if higher-order correlations are resolved in the interferogram.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pra23,

title = {Electrically controlled quantum reflection},

author = {A. R. Barnea and B. A. Stickler and O. Cheshnovsky and K. Hornberger and U. Even},

url = {https://www.klaus-hornberger.de/pdf/pra23.pdf, PDF},

doi = {10.1103/PhysRevA.95.043639},

year  = {2017},

date = {2017-04-27},

journal = {Physical Review A},

volume = {95},

pages = {043639},

abstract = {We demonstrate experimentally that an electric field can be used to control quantum reflection of matter waves off periodically microstructured surfaces. Applying a voltage of alternating polarity between neighboring grating bars induces an electric field which modifies the interaction between the surface and the impinging matter wave so that quantum reflection is gradually reduced. We find that the measured reflectivities are in good agreement with our numerical simulations and that their suppression is well captured by a simple analytic model. This experiment constitutes a step towards electrically tuned reflective diffraction elements for atomic and molecular matter waves.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{josab1,

title = {Collapse-induced Orientational Localization of Rigid Rotors},

author = {B. Schrinski and B. A. Stickler and K. Hornberger},

url = {https://www.klaus-hornberger.de/pdf/josab1.pdf, PDF},

doi = {10.1364/JOSAB.34.0000C1},

year  = {2017},

date = {2017-04-17},

journal = {Journal of the Optical Society of America B},

volume = {34},

pages = {C1-C7},

abstract = {We show how the ro-translational motion of anisotropic particles is affected by the model of Continuous Spontaneous Localization (CSL), the most prominent hypothetical modification of the Schr\"{o}dinger equation restoring realism on the macroscale. We derive the master equation describing collapse-induced spatio-orientational decoherence, and demonstrate how it leads to linear- and angular-momentum diffusion. Since the associated heating rates scale differently with the CSL parameters, the latter can be determined individually by measuring the random motion of a single levitated nanorotor.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{optica1,

title = {Full Rotational Control of Levitated Silicon Nanorods},

author = {S. Kuhn and A. Koslov and B. A. Stickler and F. Patolsky and K. Hornberger and M. Arndt and J. Millen},

url = {https://www.klaus-hornberger.de/pdf/optica1.pdf, PDF 

https://www.klaus-hornberger.de/pdf/optica1_supp.pdf, Supplementary Information},

doi = {10.1364/OPTICA.4.000356},

year  = {2017},

date = {2017-03-13},

urldate = {2017-03-13},

journal = {Optica},

volume = {4},

pages = {356-360},

abstract = {Optically levitated nano-objects in vacuum are among the highest quality mechanical oscillators, and thus of great interest for force sensing, cavity quantum optomechanics, and nanothermodynamic studies. These precision applications require exquisite control. Here, we present full control over the rotational and translational dynamics of an optically levitated silicon nanorod. We trap its center-of-mass and align it along the linear polarization of the laser field. The rod can be set into rotation at a predefined frequency by exploiting the radiation pressure exerted by elliptically polarized light. The rotational motion of the rod dynamically modifies the optical potential, which allows tuning of the rotational frequency over hundreds of kilohertz. Through nanofabrication, we can tailor all of the trapping frequencies and the optical torque, achieving reproducible dynamics that are stable over months, and analytically predict the motion with great accuracy. This first demonstration of full ro-translational control of nanoparticles in vacuum opens up the fields of rotational optomechanics, rotational ground state cooling, and the study of rotational thermodynamics in the underdamped regime.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{apb4,

title = {New avenues for matter-wave-enhanced spectroscopy},

author = {J. Rodewald and P. Haslinger and N. D\"{o}rre and B. A. Stickler and A. Shayeghi and K. Hornberger and M. Arndt},

url = {https://www.klaus-hornberger.de/pdf/apb4.pdf, PDF},

doi = {10.1007/s00340-016-6573-y},

year  = {2016},

date = {2016-12-09},

journal = {Applied Physics B},

volume = {123},

pages = {3},

abstract = {We present matter-wave interferometry as a tool to advance spectroscopy for a wide class of nanoparticles, clusters and molecules. The high sensitivity of de Broglie interference fringes to external perturbations enables measurements in the limit of an individual particle absorbing only a single photon on average, or even no photon at all. The method allows one to extract structural and electronic information from the loss of the interference contrast. It is minimally invasive and works even for dilute ensembles.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pra22,

title = {Multiphoton absorption in optical gratings for matter waves},

author = {K. Walter and S. Nimmrichter and K. Hornberger},

url = {https://www.klaus-hornberger.de/pdf/pra22.pdf, PDF},

doi = {10.1103/PhysRevA.94.043637},

year  = {2016},

date = {2016-10-20},

journal = {Physical Review A},

volume = {94},

pages = {043637},

abstract = {We present a theory for the diffraction of large molecules or nanoparticles at a standing light wave. Such particles can act as a genuine photon absorbers due to their numerous internal degrees of freedom effecting fast internal energy conversion. Our theory incorporates the interplay of three light-induced properties: the coherent phase modulation due to the dipole interaction, a nonunitary absorption-induced amplitude modulation described as a generalized measurement, and a coherent recoil splitting that resembles a quantum random walk in steps of the photon momentum. We discuss how these effects show up in near-field and far-field interference schemes, and we confirm our effective description by a dynamic evaluation of the grating interaction, which accounts for the internal states.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pra21,

title = {Spatio-Orientational Decoherence of Nanoparticles},

author = {B. A. Stickler and B. Papendell and K. Hornberger},

url = {https://www.klaus-hornberger.de/pdf/pra21.pdf, PDF},

doi = {10.1103/PhysRevA.94.033828},

year  = {2016},

date = {2016-09-16},

journal = {Physical Review A},

volume = {94},

pages = {033828},

abstract = {Motivated by trapping and cooling experiments with nonspherical nanoparticles, we discuss how their combined rotational and translational quantum state is affected by the interaction with a gaseous environment. Based on the quantum master equation in terms of orientation-dependent scattering amplitudes, we evaluate the localization rate for gas collisions off an anisotropic van der Waals-type potential and for photon scattering off an anisotropic dielectric. We also show how pure angular momentum diffusion arises from these open quantum dynamics in the limit of weak anisotropies.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{fdp1,

title = {On the role of the electric dipole moment in the diffraction of biomolecules at nanomechanical gratings},

author = {C. Knobloch and B. A. Stickler and C. Brand and M. Sclafani and Y. Lilach and T. Juffmann and O. Cheshnovsky and K. Hornberger and M. Arndt},

url = {https://www.klaus-hornberger.de/pdf/fdp1.pdf, PDF},

doi = {10.1002/prop.201600025},

year  = {2016},

date = {2016-09-12},

journal = {Fortschritte der Physik},

volume = {65},

pages = {1600025},

abstract = {We investigate effects of a permanent electric dipole moment on matter-wave diffraction at nanomechanical grids. Specifically, the diffraction patterns of hypericin at ultra-thin carbonaceous diffraction masks are compared with those of a polar and a non-polar porphyrin derivative of similar mass and de Broglie wavelength. We present a theoretical analysis of the diffraction of a rotating dipole highlighting that small local electric charges in the material mask can strongly reduce the interference visibility. We discuss the relevance of this finding for single grating diffraction and multi-grating interferometry with biomolecules.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pra20,

title = {Rotranslational Cavity Cooling of Dielectric Rods and Disks},

author = {B. A. Stickler and S. Nimmrichter and L. Martinetz and S. Kuhn and M. Arndt and K. Hornberger},

url = {https://www.klaus-hornberger.de/pdf/pra20.pdf, PDF},

doi = {10.1103/PhysRevA.94.033818},

year  = {2016},

date = {2016-09-12},

journal = {Physical Review A},

volume = {94},

pages = {033818},

abstract = {We study the interaction of dielectric rods and disks with the laser field of a high-finesse cavity. The quantum master equation for the coupled particle-cavity dynamics, including Rayleigh scattering, is derived for particle sizes comparable to the laser wavelength. We demonstrate that such anisotropic nanoparticles can be captured from free flight at velocities higher than those required to capture dielectric spheres of the same volume and that efficient rotranslational cavity cooling into the deep quantum regime is achievable.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pra19,

title = {Collisional decoherence of polar molecules},

author = {K. Walter and B. A. Stickler and K. Hornberger},

url = {https://www.klaus-hornberger.de/pdf/pra19.pdf, PDF},

doi = {10.1103/PhysRevA.93.063612},

year  = {2016},

date = {2016-06-10},

journal = {Physical Review A},

volume = {93},

pages = {063612},

abstract = {The quantum state of motion of a large and rotating polar molecule can lose coherence through the collisions with gas atoms. We show how the associated quantum master equation for the center of mass can be expressed in terms of the orientationally averaged differential and total scattering cross sections, for which we provide approximate analytic expressions. The master equation is then utilized to quantify collisional decoherence in a interference experiment with polar molecules.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pra18,

title = {Unraveling quantum Brownian motion: Pointer states and their classical trajectories},

author = {L. S\"{o}rgel and K. Hornberger},

url = {https://www.klaus-hornberger.de/pdf/pra18.pdf, PDF},

doi = {10.1103/PhysRevA.92.062112},

year  = {2015},

date = {2015-12-09},

journal = {Physical Review A},

volume = {92},

pages = {062112},

abstract = {We characterize the pointer states generated by the master equation of quantum Brownian motion and derive stochastic equations for the dynamics of their trajectories in phase space. Our method is based on a Poissonian unraveling of the master equation whose deterministic part exhibits soliton-like solutions that can be identified with the pointer states. In the semiclassical limit, their equations of motion in phase space turn into those of classical diffusion, yielding a clear picture of the quantum-classical transition induced by environmental decoherence.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pra17,

title = {Molecular rotations in matter-wave interferometry},

author = {B. A. Stickler and K. Hornberger},

url = {https://www.klaus-hornberger.de/pdf/pra17.pdf, PDF},

doi = {10.1103/PhysRevA.92.023619},

year  = {2015},

date = {2015-08-13},

journal = {Physical Review A},

volume = {92},

pages = {023619},

abstract = {We extend the theory of matter-wave interferometry of pointlike particles to nonspherical objects by taking the orientational degrees of freedom into account. In particular, we derive the grating transformation operator, which maps the impinging state onto the outgoing state, for a general, orientation-dependent interaction potential between the grating and the molecule. The grating operator is then worked out for the diffraction of symmetric top molecules from standing light waves, and the resulting interference pattern is calculated in the near field. This allows us to identify a signature of the orientational degrees of freedom in near-field matter-wave experiments.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nanolett1,

title = {Cavity-assisted manipulation of freely rotating silicon nanorods in high vacuum},

author = {S. Kuhn and P. Asenbaum and A. Kosloff and M. Sclafani and B. A. Stickler and S. Nimmrichter and K. Hornberger and O. Cheshnovsky and F. Patolsky and M. Arndt},

url = {https://www.klaus-hornberger.de/pdf/nanolett1.pdf, PDF 

 https://www.klaus-hornberger.de/pdf/nanolett1_supp.pdf, Supplementary Information},

doi = {10.1021/acs.nanolett.5b02302},

year  = {2015},

date = {2015-07-13},

journal = {Nano Letters},

volume = {15},

pages = {5604},

abstract = {Optical control of nanoscale objects has recently developed into a thriving field of research with far-reaching promises for precision measurements, fundamental quantum physics and studies on single-particle thermodynamics. Here, we demonstrate the optical manipulation of silicon nanorods in high vacuum. Initially, we sculpture these particles into a silicon substrate with a tailored geometry to facilitate their launch into high vacuum by laser-induced mechanical cleavage. We manipulate and trace their center-of-mass and rotational motion through the interaction with an intense intracavity field. Our experiments show that the anisotropy of the nanorotors leads to optical forces that are three times stronger than on silicon nanospheres of the same mass. The optical torque experienced by the spinning rods will enable cooling of the rotational motion and torsional optomechanics in a dissipation-free environment.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{natcom3,

title = {Coherence in the presence of absorption and heating in a molecule interferometer},

author = {J. P. Cotter and S. Eibenberger and L. Mairhofer and X. Cheng and P. Asenbaum and M. Arndt and K. Walter and S. Nimmrichter and K. Hornberger},

url = {https://www.klaus-hornberger.de/pdf/natcom3.pdf, PDF 

https://www.nature.com/articles/ncomms10121, Erratum},

doi = {10.1038/ncomms8336},

year  = {2015},

date = {2015-06-11},

urldate = {2015-06-11},

journal = {Nature Communications},

volume = {6},

pages = {7336},

abstract = {Matter-wave interferometry can be used to probe the foundations of physics and to enable precise measurements of particle properties and fundamental constants. It relies on beam splitters that coherently divide the wave function. In atom interferometers, such elements are often realised using lasers by exploiting the dipole interaction or through photon absorption. It is intriguing to extend these ideas to complex molecules where the energy of an absorbed photon can rapidly be redistributed across many internal degrees of freedom. Here, we provide evidence that center-of-mass coherence can be maintained even when the internal energy and entropy of the interfering particle are substantially increased by absorption of photons from a standing light wave. Each photon correlates the molecular center-of-mass wave function with its internal temperature and splits it into a superposition with opposite momenta in addition to the beam-splitting action of the optical dipole potential.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{physikj3,

title = {C\"{a}sium mag es unrealistisch},

author = {K. Hornberger},

url = {mailto:klaus-hornberger@uni-due.de, PDF available upon request 

https://www.pro-physik.de/physik-journal/april-2015-0, Journal},

year  = {2015},

date = {2015-04-01},

urldate = {2014-04-01},

journal = {Physik Journal},

volume = {14},

number = {4},

pages = {24},

abstract = {Nichtinvasive Messungen atomarer Positionen erlauben die Falsifizierung makrorealistischer Modelle.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pra16,

title = {Quantum reflection and interference of matter waves from periodically doped surfaces},

author = {B. A. Stickler and U. Even and K. Hornberger},

url = {https://www.klaus-hornberger.de/pdf/pra16.pdf, PDF},

doi = {10.1103/PhysRevA.91.013614},

year  = {2015},

date = {2015-01-13},

urldate = {2015-01-13},

journal = {Physical Review A},

volume = {91},

pages = {013614},

abstract = {We show that periodically doped, flat surfaces can act as reflective diffraction gratings for atomic and molecular matter waves. The diffraction element is realized by exploiting the fact that charged dopants locally suppress quantum reflection from the Casimir-Polder potential. We present a general quantum scattering theory for reflection off periodically charged surfaces and discuss the requirements for the observation of multiple diffraction peaks.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{prd1,

title = {Stochastic extensions of the regularized Schr\"{o}dinger-Newton equation},

author = {S. Nimmrichter and K. Hornberger},

url = {https://www.klaus-hornberger.de/pdf/prd1.pdf, PDF},

doi = {10.1103/PhysRevD.91.024016},

year  = {2015},

date = {2015-01-12},

journal = {Physical Review D},

volume = {91},

pages = {024016},

abstract = {We show that the Schr\"{o}dinger-Newton equation, which describes the nonlinear time evolution of self-gravitating quantum matter, can be made compatible with the no-signaling requirement by elevating it to a stochastic differential equation. In the deterministic form of the equation, as studied so far, the nonlinearity would lead to diverging energy corrections for localized wave packets and would create observable correlations admitting faster-than-light communication. By regularizing the divergencies and adding specific random jumps or a specific Brownian noise process, the effect of the nonlinearity vanishes in the stochastic average and gives rise to a linear and Galilean invariant evolution of the density operator.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{natcom2,

title = {Near-field interferometry of a free-falling nanoparticle from a point-like source},

author = {J. Bateman and S. Nimmrichter and K. Hornberger and H. Ulbricht},

url = {https://www.klaus-hornberger.de/pdf/natcom2.pdf, PDF 

 https://www.klaus-hornberger.de/pdf/natcom2_supp.pdf, Supplementary Information},

doi = {10.1038/ncomms5788},

year  = {2014},

date = {2014-09-02},

journal = {Nature Communications},

volume = {5},

pages = {4788},

abstract = {Matter-wave interferometry performed with massive objects elucidates their wave nature and thus tests the quantum superposition principle at large scales. Whereas standard quantum theory places no limit on particle size, alternative, yet untested theories can be conceived which forbid macroscopic superpositions. Here we propose an interferometer with a levitated, optically cooled, and then free-falling silicon nanoparticle in the mass range of one million atomic mass units delocalized over more than 150 nm. The scheme employs the near-field Talbot effect with a single standing-wave laser pulse as a phase grating. Our analysis, which accounts for all relevant sources of decoherence, indicates that this is a viable route towards macroscopic high-mass superpositions using available technology.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{prl12,

title = {Incoherent Control of the Retinal Isomerization in Rhodopsin},

author = {F. Lucas and K. Hornberger},

url = {https://www.klaus-hornberger.de/pdf/prl12.pdf, PDF},

doi = {10.1103/PhysRevLett.113.058301},

year  = {2014},

date = {2014-08-11},

urldate = {2014-08-11},

journal = {Physical Review Letters},

volume = {113},

pages = {058301},

abstract = {We propose to control the retinal photoisomerization yield through the back-action dynamics imparted by a nonselective optical measurement of the molecular electronic state. This incoherent effect is easier to implement than comparable coherent pulse shaping techniques, and is also robust to environmental noise. A numerical simulation of the quantum dynamics shows that the isomerization yield of this important biomolecule can be substantially increased above the natural limit.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{prl11,

title = {Optomechanical sensing of spontaneous wave-function collapse},

author = {S. Nimmrichter and K. Hornberger and K. Hammerer},

url = {https://www.klaus-hornberger.de/pdf/prl11.pdf, PDF 

 https://www.klaus-hornberger.de/pdf/prl11_supp.pdf, Supplementary Information 

 https://www.klaus-hornberger.de/pdf/prl11_erratum.pdf, Erratum},

doi = {10.1103/PhysRevLett.113.020405},

year  = {2014},

date = {2014-07-10},

journal = {Physical Review Letters},

volume = {113},

pages = {020405},

abstract = {Quantum experiments with nanomechanical oscillators are regarded as a test bed for hypothetical modifications of the Schr\"{o}dinger equation, which predict a breakdown of the superposition principle and induce classical behavior at the macroscale. It is generally believed that the sensitivity to these unconventional effects grows with the mass of the mechanical quantum system. Here we show that the opposite is the case for optomechanical systems in the presence of generic noise sources, such as thermal and measurement noise. We determine conditions for distinguishing these decoherence processes from possible collapse-induced decoherence in continuous optomechanical force measurements.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{naturephysics2,

title = {Testing the limits of quantum mechanical superpositions},

author = {M. Arndt and K. Hornberger},

url = {https://www.klaus-hornberger.de/pdf/naturephysics2.pdf, PDF 

 http://dx.doi.org/10.1038/nphys2934, Editorial},

doi = {10.1038/nphys2863},

year  = {2014},

date = {2014-04-01},

journal = {Nature Physics},

volume = {10},

pages = {271-277},

abstract = {Quantum physics has intrigued scientists and philosophers alike, because it challenges our notions of reality and locality \textemdash concepts that we have grown to rely on in our macroscopic world. It is an intriguing open question whether the linearity of quantum mechanics extends into the macroscopic domain. Scientific progress over the past decades inspires hope that this debate may be settled by table-top experiments.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pra15,

title = {Optimally Convergent Quantum Jump Expansion},

author = {F. Lucas and K. Hornberger},

url = {https://www.klaus-hornberger.de/pdf/pra15.pdf, PDF},

doi = {10.1103/PhysRevA.89.012112},

year  = {2014},

date = {2014-01-15},

journal = {Physical Review A},

volume = {89},

pages = {012112},

abstract = {A method for deriving accurate analytic approximations for Markovian open quantum systems was recently introduced by Lucas and Hornberger [Phys. Rev. Lett. 110 240401 (2013)]. Here, we present a detailed derivation of the underlying nonperturbative jump expansion, which involves an adaptive resummation to ensure optimal convergence. Applying this to a set of exemplary master equations, we find that the resummation typically leads to convergence within the lowest two to five orders. Besides facilitating analytic approximations, the optimal jump expansion thus provides a numerical scheme for the efficient simulation of open quantum systems.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pra14,

title = {Quantum phase space representation for curved configuration spaces},

author = {C. Gneiting and T. Fischer and K. Hornberger},

url = {https://www.klaus-hornberger.de/pdf/pra14.pdf, PDF 

https://www.klaus-hornberger.de/pdf/pra14_erratum.pdf, Erratum},

doi = {10.1103/PhysRevA.88.062117},

year  = {2013},

date = {2013-12-30},

urldate = {2013-12-30},

journal = {Physical Review A},

volume = {88},

pages = {062117},

abstract = {We extend the Wigner-Weyl-Moyal phase-space formulation of quantum mechanics to general curved configuration spaces. The underlying phase space is based on the chosen coordinates of the manifold and their canonically conjugate momenta. The resulting Wigner function displays the axioms of a quasiprobability distribution, and any Weyl-ordered operator gets associated with the corresponding phase-space function, even in the absence of continuous symmetries. The corresponding quantum Liouville equation reduces to the classical curved space Liouville equation in the semiclassical limit. We demonstrate the formalism for a point particle moving on two-dimensional manifolds, such as a paraboloid or the surface of a sphere. The latter clarifies the treatment of compact coordinate spaces, as well as the relation of the presented phase-space representation to symmetry groups of the configuration space.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{piuz3,

title = {Wann ist Schr\"{o}dingers Katze wirklich tot?},

author = {S. Nimmrichter and K. Hornberger},

url = {mailto:klaus-hornberger@uni-due.de, PDF available upon request},

doi = {10.1002/piuz.201390083},

year  = {2013},

date = {2013-09-02},

journal = {Physik in unserer Zeit},

volume = {44},

issue = {5},

pages = {214},

abstract = {Moderne Experimente best\"{a}tigen die Gesetze der Quantenmechanik auf immer gr\"{o}\sseren Skalen. Dabei stellt sich die Frage, wo der \"{U}bergang vom quantenmechanischen zum klassischen Verhalten stattfindet und ob das quantenmechanische Superpositionsprinzip seine G\"{u}ltigkeit verliert. Wir haben ein Ma\ss vorgeschlagen, das es erm\"{o}glicht, unterschiedliche quantenmechanische Experimente danach zu bewerten, wie sehr sie unser allt\"{a}gliches, klassisches Weltbild in Frage stellen.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pra13,

title = {Nonlocal Young tests with Einstein-Podolsky-Rosen-correlated particle pairs},

author = {C. Gneiting and K. Hornberger},

url = {https://www.klaus-hornberger.de/pdf/pra13.pdf, PDF},

doi = {10.1103/PhysRevA.88.013610},

year  = {2013},

date = {2013-07-08},

journal = {Physical Review A},

volume = {88},

pages = {013610},

abstract = {We evaluate the nonlocal spatial interference displayed by Einstein-Podolsky-Rosen entangled particle pairs after they pass through a double-grating arrangement. An entanglement criterion is derived which serves to certify the underlying entanglement only from the observed spatial correlations. We discuss the robustness of the scheme along with a number of possible realizations with matter waves.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{prl10,

title = {Adaptive Resummation of Markovian Quantum Dynamics},

author = {F. Lucas and K. Hornberger},

url = {https://www.klaus-hornberger.de/pdf/prl10.pdf, PDF},

doi = {10.1103/PhysRevLett.110.240401},

year  = {2013},

date = {2013-06-12},

journal = {Physical Review Letters},

volume = {110},

pages = {240401},

abstract = {We introduce a method for obtaining analytic approximations to the evolution of Markovian open quantum systems. It is based on resumming a generalized Dyson series in a way that ensures optimal convergence even in the absence of a small parameter. The power of this approach is demonstrated by two benchmark examples: the spatial detection of a free particle and the Landau-Zener problem in the presence of dephasing. The derived approximations are asymptotically exact and exhibit errors on the per mill level over the entire parameter range.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{njp3,

title = {Wigner function for the orientation state},

author = {T. Fischer and S. Nimmrichter and K. Hornberger},

url = {https://www.klaus-hornberger.de/pdf/njp3.pdf, PDF 

 http://iopscience.iop.org/1367-2630/15/6/063004/media, Movie of molecular alignment dynamics},

doi = {10.1088/1367-2630/15/6/063004},

year  = {2013},

date = {2013-06-06},

journal = {New Journal of Physics},

volume = {15},

pages = {06004},

abstract = {We introduce a quantum phase space representation for the orientation state of extended quantum objects, using the Euler angles and their conjugate momenta as phase space coordinates. It exhibits the same properties as the standard Wigner function and thus provides an intuitive framework for discussing quantum effects and semiclassical approximations in the rotational motion. Examples illustrating the viability of this quasi-probability distribution include the phase space description of a molecular alignment effect.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{prl9,

title = {Macroscopicity of mechanical quantum superposition states},

author = {S. Nimmrichter and K. Hornberger},

url = {https://www.klaus-hornberger.de/pdf/prl9.pdf, PDF 

 https://www.klaus-hornberger.de/pdf/prl9_supp.pdf, Supplementary Information 

 https://www.newscientist.com/article/mg21829144-700-quantum-effects-get-a-weirdness-scale, Featured in New Scientist 

 http://physics.aps.org/synopsis-for/10.1103/PhysRevLett.110.160403, Featured in Physics 6 (2013) 

 https://physicsworld.com/a/how-fat-is-schrodingers-cat, Featured in Physics World},

doi = {10.1103/PhysRevLett.110.160403},

year  = {2013},

date = {2013-04-18},

journal = {Physical Review Letters},

volume = {110},

pages = {160403},

abstract = {We propose an experimentally accessible, objective measure for the macroscopicity of superposition states in mechanical quantum systems. Based on the observable consequences of a minimal, macrorealist extension of quantum mechanics, it allows one to quantify the degree of macroscopicity achieved in different experiments.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{jcp1,

title = {Effect of molecular rotation on enantioseparation},

author = {A. Jacob and K. Hornberger},

url = {https://www.klaus-hornberger.de/pdf/jcp1.pdf, PDF},

doi = {10.1063/1.4738753},

year  = {2012},

date = {2012-07-31},

urldate = {2012-07-31},

journal = {Journal of Chemical Physics},

volume = {137},

pages = {044313},

abstract = {Recently, several laser schemes have been proposed to separate racemic mixtures of enantiomers by splitting a molecular beam into subbeams consisting of molecules of definite chirality [Y. Li, C. Bruder, and C. P. Sun, Phys. Rev. Lett. 99, 130403 (2007); X. Li and M. Shapiro, J. Chem. Phys. 132, 194315 (2010)]. These ideas rely on laser-induced effective gauge potentials in an adiabatic basis which lead to a chirality dependent force on the center-of-mass. However, the effect of molecular rotation has been neglected in these studies. Accounting for the full molecular quantum state we find that the potentials from the adiabatic dressed state approach cannot be recovered once the molecular orientation dynamics is included, even in the rotational ground state. This affects substantially the ability to perform enantioseparation in the above mentioned setups.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pra12,

title = {Casimir-Polder interaction of fullerene molecules with surfaces},

author = {S. Y. Buhmann and S. Scheel and S. r{A}. Ellingsen and K. Hornberger and A. Jacob},

url = {https://www.klaus-hornberger.de/pdf/pra12.pdf, PDF},

doi = {10.1103/PhysRevA.85.042513},

year  = {2012},

date = {2012-04-17},

journal = {Physical Review A},

volume = {85},

pages = {042513},

abstract = {We calculate the thermal Casimir-Polder potential of C60 and C70 fullerene molecules near gold and silicon nitride surfaces, motivated by their relevance for molecular matter wave interference experiments. We obtain the coefficients governing the asymptotic power laws of the interaction in the thermal, retarded and nonretarded distance regimes and evaluate the full potential numerically. The interaction is found to be dominated by electronic transitions, and hence independent of the internal temperature of the molecules. The contributions from phonon transitions, which are affected by the molecular temperature, give rise to only a small correction. Moreover, we find that the sizeable molecular line widths of thermal fullerenes may modify the nonretarded interaction, depending on the model used. Detailed measurements of the nonretarded potential of fullerene thus allow one to distinguish between different theories of incorporating damping.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{rmp1,

title = {Colloquium: Quantum interference of clusters and molecules},

author = {K. Hornberger and S. Gerlich and P. Haslinger and S. Nimmrichter and M. Arndt},

url = {https://www.klaus-hornberger.de/pdf/rmp1.pdf, PDF},

doi = {10.1103/RevModPhys.84.157},

year  = {2012},

date = {2012-02-08},

journal = {Reviews of Modern Physics},

volume = {84},

pages = {157-173},

abstract = {We review recent progress and future prospects of matter wave interferometry with complex organic molecules and inorganic clusters. Three variants of a near-field interference effect, based on diffraction by material nanostructures, at optical phase gratings, and at ionizing laser fields are considered. We discuss the theoretical concepts underlying these experiments and the experimental challenges. This includes optimizing interferometer designs as well as understanding the role of decoherence. The high sensitivity of matter wave interference experiments to external perturbations is demonstrated to be useful for accurately measuring internal properties of delocalized nanoparticles. We conclude by investigating the prospects for probing the quantum superposition principle in the limit of high particle mass and complexity.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{njp2,

title = {Concept of an ionizing time-domain matter-wave interferometer},

author = {S. Nimmrichter and P. Haslinger and K. Hornberger and M. Arndt},

url = {https://www.klaus-hornberger.de/pdf/njp2.pdf, PDF},

doi = {10.1088/1367-2630/13/7/075002},

year  = {2011},

date = {2011-07-05},

journal = {New Journal of Physics},

volume = {13},

pages = {075002},

abstract = {We discuss the concept of an all-optical and ionizing matter-wave interferometer in the time domain. The proposed setup aims at testing the wave nature of highly massive clusters and molecules, and it will enable new precision experiments with a broad class of atoms, using the same laser system. The propagating particles are illuminated by three pulses of a standing ultraviolet laser beam, which detaches an electron via efficient single photon-absorption. Optical gratings may have periods as small as 80 nm, leading to wide diffraction angles for cold atoms and to compact setups even for very massive clusters. Accounting for the coherent and the incoherent parts of the particle-light interaction, we show that the combined effect of phase and amplitude modulation of the matter waves gives rise to a Talbot-Lau-like interference effect with a characteristic dependence on the pulse delay time.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{prl8,

title = {Detecting entanglement in spatial interference},

author = {C. Gneiting and K. Hornberger},

url = {https://www.klaus-hornberger.de/pdf/prl8.pdf, PDF},

doi = {10.1103/PhysRevLett.106.210501},

year  = {2011},

date = {2011-05-24},

journal = {Physical Review Letters},

volume = {106},

pages = {210501},

abstract = {We discuss an experimentally amenable class of two-particle states of motion giving rise to nonlocal spatial interference under position measurements. Using the concept of modular variables, we derive a separability criterion which is violated by these non-Gaussian states. While we focus on the free motion of material particles, the presented results are valid for any pair of canonically conjugate continuous variable observables and should apply to a variety of bipartite interference phenomena.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pra11,

title = {Testing spontaneous localization theories with matter-wave interferometry},

author = {S. Nimmrichter and K. Hornberger and P. Haslinger and M. Arndt},

url = {https://www.klaus-hornberger.de/pdf/pra11.pdf, PDF},

doi = {10.1103/PhysRevA.83.043621},

year  = {2011},

date = {2011-04-07},

journal = {Physical Review A},

volume = {83},

pages = {043621},

abstract = {We propose to test the theory of continuous spontaneous localization (CSL) in an all-optical time-domain Talbot-Lau interferometer for clusters with masses exceeding 106 amu. By assessing the relevant environmental decoherence mechanisms, as well as the growing size of the particles relative to the grating fringes, we argue that it will be feasible to test the quantum superposition principle in a mass range excluded by recent estimates of the CSL effect.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{natcom1,

title = {Quantum interference of large organic molecules},

author = {S. Gerlich and S. Eibenberger and M. Tomandl and S. Nimmrichter and K. Hornberger and P. J. Fagan and J. T\"{u}xen and M. Mayor and M. Arndt},

url = {https://www.klaus-hornberger.de/pdf/natcom1.pdf, PDF 

https://www.klaus-hornberger.de/pdf/natcom1_supp.pdf, Supplementary Information},

doi = {10.1038/ncomms1263},

year  = {2011},

date = {2011-04-05},

urldate = {2011-04-05},

journal = {Nature Communications},

volume = {2},

pages = {263},

abstract = {The wave nature of matter is a key ingredient of quantum physics and yet it defies our classical intuition. First proposed by Louis de Broglie a century ago, it has since been confirmed with a variety of particles from electrons up to molecules. Here we demonstrate new high-contrast quantum experiments with large and massive tailor-made organic molecules in a near-field interferometer. Our experiments prove the quantum wave nature and delocalization of compounds composed of up to 430 atoms, with a maximal size of up to 60 r{A}, masses up to m=6,910 AMU, and de Broglie wavelengths down to λdB=h/mv≅1pm. We show that even complex systems, with more than 1,000 internal degrees of freedom, can be prepared in quantum states that are sufficiently well isolated from their environment to avoid decoherence and to show almost perfect coherence.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{fop1,

title = {New prospects for de Broglie interferometry},

author = {T. Juffmann and S. Nimmrichter and M. Arndt and H. Gleiter and K. Hornberger},

url = {https://www.klaus-hornberger.de/pdf/fop1.pdf, PDF},

doi = {10.1007/s10701-010-9520-5},

year  = {2010},

date = {2010-11-20},

journal = {Foundations of Physics},

volume = {42},

pages = {98},

abstract = {We consider various effects that are encountered in matter wave interference experiments with massive nanoparticles. The text-book example of far-field interference at a grating is compared with diffraction into the dark field behind an opaque aperture, commonly designated as Poisson's spot or the spot of Arago. Our estimates indicate that both phenomena may still be observed in a mass range exceeding present-day experiments by at least two orders of magnitude. They both require, however, the development of sufficiently cold, intense and coherent cluster beams. While the observation of Poisson's spot offers the advantage of non-dispersiveness and a simple distinction between classical and quantum fringes in the absence of particle wall interactions, van der Waals forces may severely limit the distinguishability between genuine quantum wave diffraction and classically explicable spots already for moderately polarizable objects and diffraction elements as thin as 100 nm.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{physikj1,

title = {Interferometrie mit komplexen Molek\"{u}len},

author = {M. Arndt and S. Gerlich and K. Hornberger and M. Mayor},

url = {mailto:klaus-hornberger@uni-due.de, PDF available upon request 

https://www.pro-physik.de/physik-journal/oktober-2010, Journal},

year  = {2010},

date = {2010-10-01},

urldate = {2010-10-01},

journal = {Physik Journal},

volume = {9},

number = {10},

pages = {37},

abstract = {In einem Pionierexperiment gelang es Immanuel ­Estermann und Otto Stern 1929, die Beugung von Wasserstoffmolek\"{u}len an einer Kristalloberfl\"{a}che nachzuweisen. Dieser konzeptionell einfache und elegante Versuch st\"{o}\sst bei immer komplexeren Molek\"{u}len jedoch bald an eine Grenze. Eine neue experimentelle Methode, die auf Ideen aus zwei Jahrhunderten zur\"{u}ckgeht, erlaubt es hingegen, den quantenmechanischen Welle-Teilchen-Dualismus mit Molek\"{u}len aus \"{u}ber hundert Atomen zu untersuchen. Wir verfolgen hier insbesondere die Frage, wie sich die innere Struktur und Dynamik komplexer Teilchen auf das Wellen­verhalten ihrer Schwerpunktsbewegung auswirkt. 

einklappen},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pra10,

title = {Comment on "Quantum linear Boltzmann equation with finite intercollision time"},

author = {K. Hornberger and B. Vacchini},

url = {https://www.klaus-hornberger.de/pdf/pra10.pdf, PDF},

doi = {10.1103/PhysRevA.82.036101},

year  = {2010},

date = {2010-09-27},

journal = {Physical Review A},

volume = {82},

pages = {036101},

abstract = {Inconsistencies are pointed out in a recent proposal [L. Diosi, Phys. Rev. A 80, 064104 (2009)] for a quantum version of the classical linear Boltzmann equation.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pre1,

title = {Stochastic simulation algorithm for the quantum linear Boltzmann equation},

author = {M. Busse and P. Pietrulewicz and H. -P. Breuer and K. Hornberger},

url = {https://www.klaus-hornberger.de/pdf/pre1.pdf, PDF},

doi = {10.1103/PhysRevE.82.026706},

year  = {2010},

date = {2010-08-30},

journal = {Physical Review E},

volume = {82},

pages = {026706},

abstract = {We develop a Monte Carlo wave function algorithm for the quantum linear Boltzmann equation, a Markovian master equation describing the quantum motion of a test particle interacting with the particles of an environmental background gas. The algorithm leads to a numerically efficient stochastic simulation procedure for the most general form of this integrodifferential equation, which involves a five-dimensional integral over microscopically defined scattering amplitudes that account for the gas interactions in a nonperturbative fashion. The simulation technique is used to assess various limiting forms of the quantum linear Boltzmann equation, such as the limits of pure collisional decoherence and quantum Brownian motion, the Born approximation, and the classical limit. Moreover, we extend the method to allow for the simulation of the dissipative and decohering dynamics of superpositions of spatially localized wave packets, which enables the study of many physically relevant quantum phenomena, occurring e.g., in the interferometry of massive particles.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{ospec1,

title = {Entangling the free motion of a particle pair: an experimental scenario},

author = {C. Gneiting and K. Hornberger},

url = {https://www.klaus-hornberger.de/pdf/ospec1.pdf, PDF},

doi = {10.1134/S0030400X10020074},

year  = {2010},

date = {2010-03-20},

journal = {Optics and Spectroscopy},

volume = {108},

pages = {188},

abstract = {The concept of dissociation-time entanglement provides a means of manifesting non-classical correlations in the motional state of two counter-propagating atoms. In this article, we discuss in detail the requirements for a specific experimental implementation, which is based on the Feshbach dissociation of a molecular Bose-Einstein condensate of fermionic lithium. A sequence of two magnetic field pulses serves to delocalize both of the dissociation products into a superposition of consecutive wave packets, which are separated by a macroscopic distance. This allows to address them separately in a switched Mach-Zehnder configuration, permitting to conduct a Bell experiment with simple position measurements. We analyze the expected form of the two-particle wave function in a concrete experimental setup that uses lasers as atom guides. Assuming viable experimental parameters the setup is shown to be capable of violating a Bell inequality.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pra9,

title = {Influence of conformational molecular dynamics on matter wave interferometry},

author = {M. Gring and S. Gerlich and S. Eibenberger and S. Nimmrichter and T. Berrada and M. Arndt and H. Ulbricht and K. Hornberger and M. M\"{u}ri and M. Mayor and M. B\"{o}ckmann and N. L. Doltsinis},

url = {https://www.klaus-hornberger.de/pdf/pra9.pdf, PDF 

https://www.klaus-hornberger.de/pdf/pra9_supp.pdf, Supplementary Information},

doi = {10.1103/PhysRevA.81.031604},

year  = {2010},

date = {2010-03-08},

urldate = {2010-03-08},

journal = {Physical Review A},

volume = {81},

pages = {031604(R)},

abstract = {We investigate the influence of thermally activated internal molecular dynamics on the phase shifts of matter waves inside a molecule interferometer. While de Broglie physics generally describes only the center-of-mass motion of a quantum object, our experiment demonstrates that the translational quantum phase is sensitive to dynamic conformational state changes inside the diffracted molecules. The structural flexibility of tailor-made organic particles is sufficient to admit a mixture of strongly fluctuating dipole moments. These modify the electric susceptibility and through this the quantum interference pattern in the presence of an external electric field. Detailed molecular dynamics simulations combined with density-functional theory allow us to quantify the time-dependent structural reconfigurations and to predict the ensemble-averaged square of the dipole moment which is found to be in good agreement with the interferometric result. The experiment thus opens a different perspective on matter wave interferometry, as we demonstrate here that it is possible to collect structural information about molecules even if they are delocalized over more than 100 times their own diameter.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pra8,

title = {Molecular Feshbach dissociation as a source for motionally entangled atoms},

author = {C. Gneiting and K. Hornberger},

url = {https://www.klaus-hornberger.de/pdf/pra8.pdf, PDF},

doi = {10.1103/PhysRevA.81.013423},

year  = {2010},

date = {2010-01-29},

journal = {Physical Review A},

volume = {81},

pages = {013423},

abstract = {We describe the dissociation of a diatomic Feshbach molecule due to a time-varying external magnetic field in a realistic trap and guide setting. An analytic expression for the asymptotic state of the two ultracold atoms is derived, which can serve as a basis for the analysis of dissociation protocols to generate motionally entangled states. For instance, the gradual dissociation by sequences of magnetic field pulses may delocalize the atoms into macroscopically distinct wave packets, whose motional entanglement can be addressed interferometrically. The established relation between the applied magnetic field pulse and the generated dissociation state reveals that square-shaped magnetic field pulses minimize the momentum spread of the atoms. This is required to control the detrimental influence of dispersion in a recently proposed experiment to perform a Bell test in the motion of the two atoms [Phys. Rev. Lett. 101, 260503 (2008)].},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{jpa3,

title = {Pointer basis induced by collisional decoherence},

author = {M. Busse and K. Hornberger},

url = {https://www.klaus-hornberger.de/pdf/jpa3.pdf, PDF},

doi = {10.1088/1751-8113/43/1/015303},

year  = {2009},

date = {2009-12-08},

urldate = {2009-12-08},

journal = {Journal of Physics A},

volume = {43},

pages = {015303},

abstract = {We study the emergence and dynamics of pointer states in the motion of a quantum test particle affected by collisional decoherence. These environmentally distinguished states are shown to be exponentially localized solitonic wave functions which evolve according to the classical equations of motion. We explain their formation using the orthogonal unraveling of the master equation, and we demonstrate that the statistical weights of the arising mixture are given by projections of the initial state onto the pointer basis.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{jpa2,

title = {Emergence of pointer states in a non-perturbative environment},

author = {M. Busse and K. Hornberger},

url = {https://www.klaus-hornberger.de/pdf/jpa2.pdf, PDF},

doi = {10.1088/1751-8113/42/36/362001},

year  = {2009},

date = {2009-08-19},

journal = {Journal of Physics A},

volume = {42},

pages = {362001},

abstract = {We show that the pointer basis distinguished by collisional decoherence consists of exponentially localized, solitonic wave packets. Based on the orthogonal unraveling of the quantum master equation, we characterize their formation and dynamics, and we demonstrate that the statistical weights arising from an initial superposition state are given by the required projection. Since the spatial width of the pointer states can be obtained by accounting for the gas environment in a microscopically realistic fashion, one may thus calculate the coherence length of a strongly interacting gas.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{prl7,

title = {Hund's paradox and the collisional stabilization of chiral molecules},

author = {J. Trost and K. Hornberger},

url = {https://www.klaus-hornberger.de/pdf/prl7.pdf, PDF 

 http://dx.doi.org/10.1063/1.3226702, Featured in Physics Today 

 https://www.klaus-hornberger.de/pdf/prl7_erratum.pdf, Erratum},

doi = {10.1103/PhysRevLett.103.023202},

year  = {2009},

date = {2009-07-10},

journal = {Physical Review Letters},

volume = {103},

pages = {023202},

abstract = {We identify the dominant collisional decoherence mechanism which serves to stabilize and super-select the configuration states of chiral molecules. A high-energy description of this effect is compared to the results of the exact molecular scattering problem, obtained by solving the coupled-channel equations. It allows to predict the experimental conditions for observing the collisional suppression of the tunneling dynamics between the left-handed and the right-handed configuration of D2S2 molecules.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{physrep2,

title = {Quantum linear Boltzmann equation},

author = {B. Vacchini and K. Hornberger},

url = {https://www.klaus-hornberger.de/pdf/physrep2.pdf, PDF},

doi = {10.1016/j.physrep.2009.06.001},

year  = {2009},

date = {2009-06-11},

journal = {Physics Reports},

volume = {478},

pages = {71},

abstract = {We review the quantum version of the linear Boltzmann equation, which describes in a non-perturbative fashion, by means of scattering theory, how the quantum motion of a single test particle is affected by collisions with an ideal background gas. A heuristic derivation of this Lindblad master equation is presented, based on the requirement of translation-covariance and on the relation to the classical linear Boltzmann equation. After analyzing its general symmetry properties and the associated relaxation dynamics, we discuss a quantum Monte Carlo method for its numerical solution. We then review important limiting forms of the quantum linear Boltzmann equation, such as the case of quantum Brownian motion and pure collisional decoherence, as well as the application to matter wave optics. Finally, we point to the incorporation of quantum degeneracies and self-interactions in the gas by relating the equation to the dynamic structure factor of the ambient medium, and we provide an extension of the equation to include internal degrees of freedom.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{njp1,

title = {Theory and experimental verification of Kapitza-Dirac-Talbot-Lau interferometry},

author = {K. Hornberger and S. Gerlich and H. Ulbricht and L. Hackerm\"{u}ller and S. Nimmrichter and I. V. Goldt and O. Boltalina and M. Arndt},

url = {https://www.klaus-hornberger.de/pdf/njp1.pdf, PDF},

doi = {10.1088/1367-2630/11/4/043032},

year  = {2009},

date = {2009-04-27},

journal = {New Journal of Physics},

volume = {11},

pages = {043032},

abstract = {Kapitza-Dirac-Talbot-Lau interferometry (KDTLI) has recently been established for demonstrating the quantum wave nature of large molecules. A phase space treatment permits us to derive closed equations for the near-field interference pattern, as well as for the Moire-type pattern that would arise if the molecules were to be treated as classical particles. The model provides a simple and elegant way to account for the molecular phase shifts related to the optical dipole potential as well as for the incoherent effect of photon absorption at the second grating. We present experimental results for different molecular masses, polarizabilities and absorption cross sections using fullerenes and fluorofullerenes and discuss the alignment requirements. Our results with C60, C70, C60F36 and C60F48 verify the theoretical description to a high degree of precision.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{apb3,

title = {Nonclassical correlations from dissociation-time entanglement},

author = {C. Gneiting and K. Hornberger},

url = {https://www.klaus-hornberger.de/pdf/apb3.pdf, PDF},

doi = {10.1007/s00340-009-3457-4},

year  = {2009},

date = {2009-03-14},

journal = {Applied Physics B},

volume = {95},

pages = {237},

abstract = {We discuss a strongly entangled two-particle state of motion that emerges naturally from the double-pulse dissociation of a diatomic molecule. This state, which may be called dissociation-time entangled, permits the unambiguous demonstration of non-classical correlations by violating a Bell inequality based on switched single particle interferometry and only position measurements. We apply time-dependent scattering theory to determine the detrimental effect of dispersion. The proposed setup brings into reach the possibility of establishing non-classical correlations with respect to system properties that are truly macroscopically distinct.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{prl6,

title = {Bell test for the free motion of material particles},

author = {C. Gneiting and K. Hornberger},

url = {https://www.klaus-hornberger.de/pdf/prl6.pdf, PDF},

doi = {10.1103/PhysRevLett.101.260503},

year  = {2008},

date = {2008-12-24},

journal = {Physical Review Letters},

volume = {101},

pages = {260503},

abstract = {We present a scheme to establish non-classical correlations in the motion of two macroscopically separated massive particles without resorting to entanglement in their internal degrees of freedom. It is based on the dissociation of a diatomic molecule with two temporally separated Feshbach pulses generating a motional state of two counter-propagating atoms that is capable of violating a Bell inequality by means of correlated single particle interferometry. We evaluate the influence of dispersion on the Bell correlation, showing it to be important but manageable in a proposed experimental setup. The latter employs a molecular BEC of fermionic Lithium atoms, uses laser-guided atom interferometry, and seems to be within the reach of present-day technology.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pra7,

title = {Absolute absorption spectroscopy based on molecule interferometry},

author = {S. Nimmrichter and K. Hornberger and H. Ulbricht and M. Arndt},

url = {https://www.klaus-hornberger.de/pdf/pra7.pdf, PDF},

doi = {10.1103/PhysRevA.78.063607},

year  = {2008},

date = {2008-12-09},

journal = {Physical Review A},

volume = {78},

pages = {063607},

abstract = {We propose a new method to measure the absolute photon absorption cross section of neutral molecules in a molecular beam. It is independent of our knowledge of the particle beam density, nor does it rely on photo-induced fragmentation or ionization. The method is based on resolving the recoil resulting from photon absorption by means of near-field matter-wave interference, and it thus applies even to very dilute beams with low optical densities. Our discussion includes the possibility of internal state conversion as well as fluorescence. We assess the influence of various experimental uncertainties and show that the measurement of absolute absorption cross sections is conceivable with high precision and using existing technologies.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pra6,

title = {Theory of near-field matter wave interference beyond the eikonal approximation},

author = {S. Nimmrichter and K. Hornberger},

url = {https://www.klaus-hornberger.de/pdf/pra6.pdf, PDF},

doi = {10.1103/PhysRevA.78.023612},

year  = {2008},

date = {2008-08-06},

journal = {Physical Review A},

volume = {78},

pages = {023612},

abstract = {A generalized description of Talbot-Lau interference with matter waves is presented, which accounts for arbitrary grating interactions and realistic beam characteristics. The dispersion interaction between the beam particles and the optical elements strongly influences the interference pattern in this near-field effect, and it is known to dominate the fringe visibility if increasingly massive and complex particles are used. We provide a general description of the grating interaction process by combining semiclassical scattering theory with a phase space formulation. It serves to systematically improve the eikonal approximation used so far, and to assess its regime of validity.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{angewchem1,

title = {Matter-Wave Metrology as a Complementary Tool for Mass Spectroscopy},

author = {S. Gerlich and M. Gring and H. Ulbricht and K. Hornberger and J. T\"{u}xen and M. Mayor and M. Arndt},

url = {https://www.klaus-hornberger.de/pdf/angewchem1.pdf, PDF 

 https://doi.org/10.1002/anie.200803290, Featured in Angew. Chem. Int. Ed 

 https://doi.org/10.1002/ange.200801942, German Version [Angew. Chem. 120 p. 6290-6293 (2008)]},

doi = {10.1002/anie.200801942},

year  = {2008},

date = {2008-07-29},

journal = {Angewandte Chemie},

volume = {47},

pages = {6195},

abstract = {Quantum interferometry can serve as a useful complement to mass spectrometry. The interferogram reveals important information on molecular properties, such as mass and polarizability. The method is applicable to a wide range of molecular species and it is particularly valuable for characterizing neutral molecular beams. The proof-of-principle experiment shows that for complex molecules, matter-wave interferometry allows fragmentation in the source to be distinguished from molecular dissociation in the detector stage.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pra5,

title = {Monitoring derivation of the quantum linear Boltzmann equation},

author = {K. Hornberger and B. Vacchini},

url = {https://www.klaus-hornberger.de/pdf/pra5.pdf, PDF},

doi = {10.1103/PhysRevA.77.022112},

year  = {2008},

date = {2008-02-19},

journal = {Physical Review A},

volume = {77},

pages = {022112},

abstract = {We show how the effective equation of motion for a distinguished quantum particle in an ideal gas environment can be obtained by means of the monitoring approach introduced in [EPL 77, 50007 (2007)]. The resulting Lindblad master equation accounts for the quantum effects of the scattering dynamics in a non-perturbative fashion and it describes decoherence and dissipation in a unified framework. It incorporates various established equations as limiting cases and reduces to the classical linear Boltzmann equation once the state is diagonal in momentum.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{epj1,

title = {Relaxation dynamics of a quantum Brownian particle in an ideal gas},

author = {B. Vacchini and K. Hornberger},

url = {https://www.klaus-hornberger.de/pdf/epj1.pdf, PDF},

doi = {10.1140/epjst/e2007-00362-9},

year  = {2007},

date = {2007-12-01},

urldate = {2007-12-01},

journal = {European Physical Journal Special Topics},

volume = {151},

pages = {59-72},

abstract = {We show how the quantum analog of the Fokker-Planck equation for describing Brownian motion can be obtained as the diffusive limit of the quantum linear Boltzmann equation. The latter describes the quantum dynamics of a tracer particle in a dilute, ideal gas by means of a translation-covariant master equation. We discuss the type of approximations required to obtain the generalized form of the Caldeira-Leggett master equation, along with their physical justification. Microscopic expressions for the diffusion and relaxation coefficients are obtained by analyzing the limiting form of the equation in both the Schr\"{o}dinger and the Heisenberg picture.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{apb2,

title = {Optical polarizabilities of large molecules measured in near-field interferometry},

author = {L. Hackerm\"{u}ller and K. Hornberger and S. Gerlich and M. Gring and H. Ulbricht and M. Arndt},

url = {https://www.klaus-hornberger.de/pdf/apb2.pdf, PDF},

doi = {10.1007/s00340-007-2873-6},

year  = {2007},

date = {2007-11-23},

journal = {Applied Physics B},

volume = {89},

pages = {469-473},

abstract = {We discuss a novel application of matter wave interferometry to characterize the scalar optical polarizability of molecules at 532 nm. The interferometer presented here consists of two material absorptive gratings and one central optical phase grating. The interaction of the molecules with the standing light wave is determined by the optical dipole force and is therefore directly dependent on the molecular polarizability at the wavelength of the diffracting laser light. By comparing the observed matter-wave interference contrast with a theoretical model for several intensities of the standing light wave and molecular velocities we can infer the polarizability in this first proof-of-principle experiment for the fullerenes C60 and C70 and we find a good agreement with literature values.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{naturephysics1,

title = {A Kapitza-Dirac-Talbot-Lau interferometer for highly polarizable molecules},

author = {S. Gerlich and L. Hackerm\"{u}ller and K. Hornberger and A. Stibor and H. Ulbricht and M. Gring and F. Goldfarb and T. Savas and M. M\"{u}ri and M. Mayor and M. Arndt},

url = {https://www.klaus-hornberger.de/pdf/naturephysics1.pdf, PDF 

https://www.klaus-hornberger.de/pdf/naturephysics1_supp.pdf, Supplementary Information 

http://dx.doi.org/10.1038/448842a, Featured in Nature 448 p. 842 (2007)},

doi = {10.1038/nphys701},

year  = {2007},

date = {2007-08-19},

urldate = {2007-08-19},

journal = {Nature Physics},

volume = {3},

pages = {711-715},

abstract = {Research on matter waves is a thriving field of quantum physics and has recently stimulated many investigations with electrons, neutrons, atoms, Bose-condensed ensembles, cold clusters and hot molecules. Coherence experiments with complex objects are of interest for exploring the transition to classical physics, for measuring molecular properties, and they have even been proposed for testing new models of space-time. For matter-wave experiments with complex molecules, the strongly dispersive effect of the interaction between the diffracted molecule and the grating wall is a major challenge because it imposes enormous constraints on the velocity selection of the molecular beam. Here, we describe the first experimental realization of a new set-up that solves this problem by combining the advantages of a so-called Talbot-Lau interferometer with the benefits of an optical phase grating.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{chemphys1,

title = {The twisted arc model for chiral molecules},

author = {J. Trost and K. Hornberger},

url = {https://www.klaus-hornberger.de/pdf/chemphys1.pdf, PDF},

doi = {10.1016/j.chemphys.2007.04.005},

year  = {2007},

date = {2007-04-20},

journal = {Chemical Physics},

volume = {335},

pages = {115-123},

abstract = {We present a simple model for chiral molecules which yields the frequency-dependent multipole-multipole polarizabilities required for calculating the dispersive van der Waals constants in a simple, closed, and consistent form. The model consists of a single effective charge confined to a one-dimensional wire formed by two circular arcs, which are twisted with respect to each other by an angle characterizing the chirality. The resulting polarizabilities show a simple functional dependence on the model parameters, and they serve to mimic the chiral properties of small molecules, such as H2S2, in a reasonably realistic way.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{epl2,

title = {Monitoring approach to open quantum dynamics using scattering theory},

author = {K. Hornberger},

url = {https://www.klaus-hornberger.de/pdf/epl2.pdf, PDF

https://www.klaus-hornberger.de/pdf/epl2_erratum.pdf, Erratum},

doi = {10.1209/0295-5075/77/50007},

year  = {2007},

date = {2007-02-27},

urldate = {2007-02-27},

journal = {Europhysics Letters},

volume = {77},

pages = {50007},

abstract = {It is shown how S-matrix theory and the concept of continuous quantum measurements can be combined to yield Markovian master equations which describe the environmental interaction non-perturbatively. The method is then applied to obtain the master equation for the effects of a gas on the internal dynamics of an immobile complex quantum system, such as a trapped molecule, in terms of the exact multi-channel scattering amplitudes.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{prl5,

title = {Master Equation for a Quantum Particle in a Gas},

author = {K. Hornberger},

url = {https://www.klaus-hornberger.de/pdf/prl5.pdf, PDF},

doi = {10.1103/PhysRevLett.97.060601},

year  = {2006},

date = {2006-08-07},

journal = {Physical Review Letters},

volume = {97},

pages = {060601},

abstract = {The equation for the quantum motion of a Brownian particle in a gaseous environment is derived by means of S-matrix theory. This quantum version of the linear Boltzmann equation accounts nonperturbatively for the quantum effects of the scattering dynamics and describes decoherence and dissipation in a unified framework. As a completely positive master equation it incorporates both the known equation for an infinitely massive Brownian particle and the classical linear Boltzmann equation as limiting cases.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pra4,

title = {Thermal limitation of far-field matter-wave interference},

author = {K. Hornberger},

url = {https://www.klaus-hornberger.de/pdf/pra4.pdf, PDF},

doi = {10.1103/PhysRevA.73.052102},

year  = {2006},

date = {2006-05-08},

journal = {Physical Review A},

volume = {73},

pages = {052102},

abstract = {We assess the effect of the heat radiation emitted by mesoscopic particles on their ability to show interference in a double slit arrangement. The analysis is based on a stationary, phase-space based description of matter wave interference in the presence of momentum-exchange mediated decoherence.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{aamop1,

title = {Quantum Chaos, Transport and Control - in quantum optics},

author = {J. Madronero and A. Ponomarev and A. R. R. Carvalho and S. Wimberger and C. Viviescas and A. Kolovsky and K. Hornberger and P. Schlagheck and A. Krug and A. Buchleitner},

url = {https://www.klaus-hornberger.de/pdf/aamop1.pdf, PDF},

doi = {10.1016/S1049-250X(06)53002-2},

year  = {2006},

date = {2006-01-01},

urldate = {2006-01-01},

journal = {Advances in Atomic, Molecular, and Optical Physics},

volume = {53},

pages = {33-73},

publisher = {Elsevier},

address = {Amsterdam},

abstract = {Chaos implies unpredictability, fluctuations, and the need for statistical modelling. Quantum optics has developed into one of the most advanced subdisciplines of modern physics in terms of the control of matter on a microscopic scale, and, in particular, of isolated, single quantum objects. Prima facie, both fields therefore appear rather distant in philosophy and outset. However, as we shall discuss in the present review, chaos, and, more specifically, quantum chaos opens up novel perspectives for our understanding of the dynamics of increasingly complex quantum systems, and of ultimate quantum control by tailoring complexity.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{piuz1,

title = {Wann wird ein Quantenobjekt klassisch? Interferenzexperimente mit molekularen Quantenwellen},

author = {M. Arndt and L. Hackerm\"{u}ller and K. Hornberger},

url = {mailto:klaus-hornberger@uni-due.de, PDF available upon request},

doi = {10.1002/piuz.200501091},

year  = {2005},

date = {2005-12-16},

urldate = {2005-12-16},

journal = {Physik in unserer Zeit},

volume = {37},

issue = {1},

pages = {24-29},

abstract = {Moderne Interferenzexperimente zeigen die quantenmechanische Wellennatur gro\sser, einzelner Molek\"{u}le. Bislang wurden Fullerene und Biomolek\"{u}le untersucht, die aus mehr als hundert Atomen bestehen. Die De-Broglie-Wellenl\"{a}nge solcher Molek\"{u}le liegt bei wenigen Tausendstel ihres Durchmessers. Seit kurzem l\"{a}sst sich auch im Detail beobachten, wie verschiedene Wechselwirkungen der Molek\"{u}le mit ihrer Umgebung zum Verlust der Quanteneigenschaften f\"{u}hren: Nach erfolgter Dekoh\"{a}renz unterscheiden sich die Molek\"{u}le nicht mehr von “klassischen” Teilchen. Bislang wurden dabei zwei Wechselwirkungsmechanismen untersucht: St\"{o}\sse mit anderen Molek\"{u}len und das Aussenden von Photonen durch W\"{a}rmestrahlung.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{physicsworld1,

title = {Probing the limits of the quantum world},

author = {M. Arndt and K. Hornberger and A. Zeilinger},

url = {mailto:klaus.hornberger@uni-due.de, PDF available upon request},

doi = {10.1088/2058-7058/18/3/28},

year  = {2005},

date = {2005-03-01},

urldate = {2005-03-01},

journal = {Physics World},

volume = {18},

number = {3},

pages = {35},

abstract = {Ever since quantum theory was developed during the first quarter of the 20th century, we have lived with a strange division. Objects in our daily lives behave "normally" \textendash they appear to obey classical physics \textendash whereas microscopic objects can behave counter-intuitively and reveal intriguing features of quantum physics. But where exactly is the boundary between the quantum and classical worlds \textendash if, indeed, there is one? If quantum physics is a universal theory, why is it respectable to talk about the quantum behaviour of electrons but not, say, of footballs?},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pra3,

title = {Influence of molecular temperature on the coherence of fullerenes in a near-field interferometer},

author = {K. Hornberger and L. Hackerm\"{u}ller and M. Arndt},

url = {https://www.klaus-hornberger.de/pdf/pra3.pdf, PDF},

doi = {10.1103/PhysRevA.71.023601},

year  = {2005},

date = {2005-02-03},

journal = {Physical Review A},

volume = {71},

pages = {023601},

abstract = {We study C70 fullerene matter waves in a Talbot-Lau interferometer as a function of their temperature. While the ideal fringe visibility is observed at moderate molecular temperatures, we find a gradual degradation of the interference contrast if the molecules are heated before entering the interferometer. A method is developed to assess the distribution of the micro-canonical temperatures of the molecules in free flight. This way the heating-dependent reduction of interference contrast can be compared with the predictions of quantum theory. We find that the observed loss of coherence agrees quantitatively with the expected decoherence rate due to the thermal radiation emitted by the hot molecules.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{laserphys,

title = {Talbot-Lau interferometry with fullerenes: Sensitivity to inertial forces and vibrational dephasing},

author = {A. Stibor and K. Hornberger and L. Hackerm\"{u}ller and A. Zeilinger and M. Arndt},

url = {https://www.klaus-hornberger.de/pdf/laserphys.pdf, PDF},

doi = {10.48550/arXiv.quant-ph/0411118},

year  = {2005},

date = {2005-01-01},

journal = {Laser Physics},

volume = {15},

pages = {10-17},

abstract = {We discuss matter wave experiments in a near-field interferometer and focus on dephasing phenomena due to inertial forces. Their presence may result in a significant reduction of the observed interference contrast, even though they do not lead to genuine decoherence. We provide quantitative estimates for the most important effects and demonstrate experimentally the strong influence of acoustic vibrations. Since the effects of inertial forces get increasingly important for the interferometry with more massive particles they have to be identified and compensated in future experiments.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pra2,

title = {Theory of decoherence in a matter wave Talbot-Lau interferometer},

author = {K. Hornberger and J. E. Sipe and M. Arndt},

url = {https://www.klaus-hornberger.de/pdf/pra2.pdf, PDF},

doi = {10.1103/PhysRevA.70.053608},

year  = {2004},

date = {2004-11-11},

journal = {Physical Review A},

volume = {70},

pages = {053608},

abstract = {We present a theoretical framework to describe the effects of decoherence on matter waves in Talbot-Lau interferometry. Using a Wigner description of the stationary beam the loss of interference contrast can be calculated in closed form. The formulation includes both the decohering coupling to the environment and the coherent interaction with the grating walls. It facilitates the quantitative distinction of genuine quantum interference from the expectations of classical mechanics. We provide realistic microscopic descriptions of the experimentally relevant interactions in terms of the bulk properties of the particles and show that the treatment is equivalent to solving the corresponding master equation in paraxial approximation.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nature1,

title = {Decoherence of matter waves by thermal emission of radiation},

author = {L. Hackerm\"{u}ller and K. Hornberger and B. Brezger and A. Zeilinger and M. Arndt},

url = {https://www.klaus-hornberger.de/pdf/nature1.pdf, PDF 

 https://doi.org/10.1126/science.303.5661.1119a, Featured in Science 

 https://www.pro-physik.de/physik-journal/april-2004#section-150326, Featured in Physik Journal 

 https://doi.org/10.1063/1.1768665, Featured in Physics Today 

 https://www.newscientist.com/issue/2447, Featured in New Scientist},

doi = {10.1038/nature02276},

year  = {2004},

date = {2004-02-19},

journal = {Nature},

volume = {427},

pages = {711-714},

abstract = {Emergent quantum technologies have led to increasing interest in decoherence - the processes that limit the appearance of quantum effects and turn them into classical phenomena. One important cause of decoherence is the interaction of a quantum system with its environment, which 'entangles' the two and distributes the quantum coherence over so many degrees of freedom as to render it unobservable. Decoherence theory has been complemented by experiments using matter waves coupled to external photons or molecules, and by investigations using coherent photon states, trapped ions and electron interferometers. Large molecules are particularly suitable for the investigation of the quantum-classical transition because they can store much energy in numerous internal degrees of freedom; the internal energy can be converted into thermal radiation and thus induce decoherence. Here we report matter wave interferometer experiments in which C70 molecules lose their quantum behaviour by thermal emission of radiation. We find good quantitative agreement between our experimental observations and microscopic decoherence theory. Decoherence by emission of thermal radiation is a general mechanism that should be relevant to all macroscopic bodies.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{apb1,

title = {Decoherence in a Talbot-Lau interferometer: the influence of molecular scattering},

author = {L. Hackerm\"{u}ller and K. Hornberger and B. Brezger and A. Zeilinger and M. Arndt},

url = {https://www.klaus-hornberger.de/pdf/apb1.pdf, PDF},

doi = {10.1007/s00340-003-1312-6},

year  = {2003},

date = {2003-12-01},

journal = {Applied Physics B},

volume = {77},

pages = {781-787},

abstract = {We study the interference of C70 fullerenes in a Talbot-Lau interferometer with a large separation between the diffraction gratings. This permits the observation of recurrences of the interference contrast both as a function of the de Broglie wavelength and in dependence of the interaction with background gases. We observe an exponential decrease of the fringe visibility with increasing background pressure and find good quantitative agreement with the predictions of decoherence theory. From this we extrapolate the limits of matter wave interferometry and conclude that the influence of collisional decoherence may be well under control in future experiments with proteins and even larger objects.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{prl4,

title = {Wave nature of biomolecules and fluorofullerenes},

author = {L. Hackerm\"{u}ller and S. Uttenthaler and K. Hornberger and E. Reiger and B. Brezger and A. Zeilinger and M. Arndt},

url = {https://www.klaus-hornberger.de/pdf/prl4.pdf, PDF},

doi = {10.1103/PhysRevLett.91.090408},

year  = {2003},

date = {2003-08-28},

journal = {Physical Review Letters},

volume = {91},

pages = {090408},

abstract = {We demonstrate quantum interference for tetraphenylporphyrin, the first biomolecule exhibiting wave nature, and for the fluorofullerene C60F48 using a near-field Talbot-Lau interferometer. For the porphyrins, which are distinguished by their low symmetry and their abundant occurence in organic systems, we find the theoretically expected maximal interference contrast and its expected dependence on the de Broglie wavelength. For C60F48 the observed fringe visibility is below the expected value, but the high contrast still provides good evidence for the quantum character of the observed fringe pattern. The fluorofullerenes therefore set the new mark in complexity and mass (1632 amu) for de Broglie wave experiments, exceeding the previous mass record by a factor of two.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pra1,

title = {Collisional decoherence reexamined},

author = {K. Hornberger and J. E. Sipe},

url = {https://www.klaus-hornberger.de/pdf/pra1.pdf, PDF},

doi = {10.1103/PhysRevA.68.012105},

year  = {2003},

date = {2003-07-21},

journal = {Physical Review A},

volume = {68},

pages = {012105},

abstract = {We rederive the quantum master equation for the decoherence of a massive Brownian particle due to collisions with the lighter particles from a thermal environment. Our careful treatment avoids the occurrence of squares of Dirac delta functions. It leads to a decoherence rate which is smaller by a factor of 2π compared to previous findings. This result, which is in agreement with recent experiments, is confirmed by both a physical analysis of the problem and by a perturbative calculation in the weak coupling limit.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{prl3,

title = {Collisional decoherence observed in matter wave interferometry},

author = {K. Hornberger and S. Uttenthaler and B. Brezger and L. Hackerm\"{u}ller and M. Arndt and A. Zeilinger},

url = {https://www.klaus-hornberger.de/pdf/prl3.pdf, PDF},

doi = {10.1103/PhysRevLett.90.160401},

year  = {2003},

date = {2003-04-22},

journal = {Physical Review Letter},

volume = {90},

pages = {160401},

abstract = {We study the loss of spatial coherence in the extended wave function of fullerenes due to collisions with background gases. From the gradual suppression of quantum interference with increasing gas pressure we are able to support quantitatively both the predictions of decoherence theory and our picture of the interaction process. We thus explore the practical limits of matter wave interferometry at finite gas pressures and estimate the required experimental vacuum conditions for interferometry with even larger objects.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{physrep1,

title = {Magnetic Edge States},

author = {K. Hornberger and U. Smilansky},

url = {https://www.klaus-hornberger.de/pdf/physrep1.pdf, PDF},

doi = {10.1016/S0370-1573(02)00141-2},

year  = {2002},

date = {2002-05-28},

journal = {Physics Reports},

volume = {367},

pages = {249-385},

abstract = {Magnetic edge states are responsible for various phenomena of magneto- transport. Their importance is due to the fact that, unlike the bulk of the eigenstates in a magnetic system, they carry electric current along the boundary of a confined domain. Edge states can exist both as interior (quantum dot) and exterior (anti-dot) states. In the present report we develop a consistent and practical spectral theory for the edge states encountered in magnetic billiards. It provides an objective definition for the notion of edge states, is applicable for interior and exterior problems, facilitates efficient quantization schemes, and forms a convenient starting point for both the semiclassical description and the statistical analysis. After elaborating these topics we use the semiclassical spectral theory to uncover nontrivial spectral correlations between the interior and the exterior edge states. We show that they are the manifestation of a duality between the classical trajectories of interior and exterior magnetic billiards.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{prl2,

title = {Spectral cross correlations of magnetic edge states},

author = {K. Hornberger and U. Smilansky},

url = {https://www.klaus-hornberger.de/pdf/prl2.pdf, PDF},

doi = {10.1103/PhysRevLett.88.024101},

year  = {2001},

date = {2001-12-26},

journal = {Physical Review Letters},

volume = {88},

pages = {024101},

abstract = {We observe strong, non-trivial cross-correlations between the edge states found in the interior and the exterior of magnetic quantum billiards. Our analysis is based on a novel definition of the edge state spectral density which is rigorous, practical and semiclassically accessible.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nobel_scripta,

title = {The exterior and interior edge states of magnetic billiards: spectral statistics and correlations},

author = {K. Hornberger and U. Smilansky},

url = {https://www.klaus-hornberger.de/pdf/nobel_scripta.pdf, PDF},

doi = {10.1238/Physica.Topical.090a00064},

year  = {2001},

date = {2001-01-01},

journal = {Physica Scripta},

volume = {T90},

pages = {64-74},

abstract = {We study the properties of quantum states in the interior and the exterior of magnetic billiards. A weight is associated to each state, providing an objective criterion to distinguish between bulk and edge states. We define a spectral density of edge states, which is then studied statistically and semiclassically. In particular, we observe strong cross-correlations between the interior and exterior edge spectra. They are identified as the quantum signature of a classical duality of periodic orbits.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{jpa1,

title = {The boundary integral method for magnetic billiards},

author = {K. Hornberger and U. Smilansky},

url = {https://www.klaus-hornberger.de/pdf/jpa1.pdf, PDF},

doi = {10.1088/0305-4470/33/14/315},

year  = {2000},

date = {2000-01-01},

journal = {Journal of Physics A},

volume = {33},

pages = {2829-2855},

abstract = {We introduce a boundary integral method for two-dimensional quantum billiards subjected to a constant magnetic field. It allows to calculate spectra and wave functions, in particular at strong fields and semiclassical values of the magnetic length. The method is presented for interior and exterior problems with general boundary conditions. We explain why the magnetic analogues of the field-free single and double layer equations exhibit an infinity of spurious solutions and how these can be eliminated at the expense of dealing with (hyper-)singular operators. The high efficiency of the method is demonstrated by numerical calculations in the extreme semiclassical regime.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{prl1,

title = {Comment on "Physical Reality of Light-Induced Atomic States"},

author = {P. Schlagheck and K. Hornberger and A. Buchleitner},

url = {https://www.klaus-hornberger.de/pdf/prl1.pdf, PDF},

doi = {10.1103/PhysRevLett.82.664},

year  = {1998},

date = {1998-06-04},

journal = {Physical Review Letters},

volume = {82},

pages = {664},

abstract = {A Comment on the Letter by J. C. Wells, I. Simbotin, and M. Gavrila, Phys. Rev. Lett. 80, 3479 (1998). The authors of the Letter offer a Reply.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{epl1,

title = {Radiative Decay of Nondispersive Wave Packets},

author = {K. Hornberger and A. Buchleitner},

url = {https://www.klaus-hornberger.de/pdf/epl1.pdf, PDF},

doi = {10.1209/epl/i1998-00161-8},

year  = {1998},

date = {1998-02-15},

journal = {Europhysics Letters},

volume = {41},

pages = {383-388},

abstract = {We study the decay of nondispersive electronic wave packets in strongly driven hydrogen atoms, which are coupled to the atomic continuum and to the vacuum modes of the electromagnetic field. A novel implementation of complex scaling allows to derive a master equation that incorporates the interplay of the coherent and the incoherent decay process. Ample numerical data predict a crossover from ionization via chaos-assisted tunneling to radiative decay, at experimentally accessible Rydberg levels.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}