Hornberger group - Welcome
Welcome to our website
We are exploring the complex dynamics of open nanoscale quantum systems, partly in collaboration with leading experimentalists.
Current projects focus on the study of coherence and entanglement phenomena in nanomechanical systems and molecular matter waves, and on the microscopic mechanisms that effect their quantum-to-classical transition.
April 23, 2021
Nanoparticles in the quantum ground state
An elliptically polarized laser beam tuned to an optical cavity can cool a nanoparticle to the quantum groundstate of its rotational and linear motion.
December 11, 2020
Quantum electromechanics with charged nanoparticles
Nanoparticles levitating in a Paul trap can be prepared and observed in quantum superposition by interfacing the endcap electrodes with a Cooper-pair box.
July 16, 2020
A Beam Splitter for Large Organic Molecules
The demonstration of Bragg diffraction of organic molecules off a standing laser beam paves the way to molecular interferometers with large path separation.
June 6, 2020
Dissertation Award for Björn Schrinski
Björn Schrinski was awarded the prize for the best PhD thesis from the Faculty of Physics. The award certificate was bestowed by the Rector of the University of Duisburg-Essen, Prof. Ulrich Radtke, at the Dies Academicus.
June 6, 2020
Thesis Award for Henning Rudolph
Henning Rudolph was awarded the prize for the best master thesis from the Faculty of Physics. The award certificate was bestowed by the Rector of the University of Duisburg-Essen, Prof. Ulrich Radtke, at the Dies Academicus.
May 6, 2020
Orbital angular momentum interference
A novel interference scheme for matter waves is based on the quanitzation of orbital anular momentum.
Physical Review Research 2, 022030 (2020) (Rapid Communication)
February 29, 2020
Poster award for Björn Schrinski
Björn Schrinski received the Best Poster Award for his poster presentation on the International Conference on Quantum Optics 2020.
January 29, 2020
Entangling levitated nanoparticles
An entangeld quantum state of two nanoparticles can be realistically demonstrated by levitating them with optical tweezers in a laser cavity.
Physical Review A 101, 011804 (2020) (Rapid Communication)
October 25, 2019
Marduk Bolaños Puchet, Ph.D.
Habemus etiam doctorem! Marduk Bolaños received a Ph.D. from the Faculty of Physics for his dissertation on the Decoherence of non-relativistic bosonic quantum fields.
September 24, 2019
Björn Schrinski, Ph.D.
Habemus doctorem! Björn Schrinski received a Ph.D. from the Faculty of Physics for his dissertation on Assessing the macroscopicity of quantum mechanical superposition tests via hypothesis falsification.
September 16, 2019
Schrödinger's cat put on the scale
We establish an objective scheme to determine the degree of macroscopicity reached in quantum mechanical superposition tests, i.e. the size of an experimentally realized Schrödinger's cat. Based on the Bayesian falsification of macrorealistic modifications, it uses the raw data of an experiment, taking into account all measurement uncertainties.
Applying the measure to advanced matter-wave experiments with Bose-Einstein-condensed atoms and large molecules shows that these reach the highest macroscpicities:
29 Jul - 1 Aug 2019
Workshop on Levitated Optomechanics
A WE-Heraeus seminar on Levitated Optomechanicswas held at Physikzentrum Bad Honnef, Germany on 29 Jul - 1 Aug 2019 (organized by K. Hornberger, J. Millen, and M. Arndt).
The seminar brought together leading scientists and young researchers working on the control of nanoparticles suspended in vacuum by optical or electric forces. The most recent advances were discussed of cooling untethered nano-mechanical systems into the quantum regime and of observing their rotranslational motion in the quantum-classical borderlands, as well as the perspectives of harnessing their coherent quantum dynamics for fundamental experiments and technological applications.
June 27, 2019
November 20, 2018
Coherence of molecular superrotors
Decoherence theory explains the surprising stability of the alignment of rapidly rotating molecules, in excellent quantitative agreement with the experimental observation.
October 29, 2018
Orientational quantum superpositions of nanoscale rotors
In a recent preprint, we propose an experimentally viable scheme to probe orientational quantum revivals with nanoscale particles, an interference effect of the rotational degrees of freedom testifying a superposition of all orientations. This opens the door to tests of rotational quantum physics with submicron objects and to quantum gyroscopic torque sensors.
New Journal of Physics 20, 122001 (2018) (Fast Track Communication)
September 17, 2018
Conformer-selection by matter-wave interference
In almost all larger molecules, the spatial arrangement of the atoms can show up in different geometries, even with all binding links equal. We show that such conformers can be selected from a mixture using a matter-wave interferometer.
July 3, 2018
Best Talk Award for Björn Schrinski
At the Bayesian Young Statisticians Meeting (BAYSM 2018) in Warwick (UK) Björn Schrinski gave a lecture entitled "Towards Bayesian hypothesis testing of macrorealistic modifications of quantum mechanics", and he duly received a Best Talk Award for his presentation.
June 15, 2018
Rotational friction and diffusion of quantum rotors
We present the general quantum description of friction, diffusion, decoherence, and thermalization in the rotational motion of rigid bodies. In the semiclassical limit, one obtains the classical Fokker-Planck equation for the rotational dynamics of a top.
June 15, 2018
Thesis Award for Lukas Martinetz
Lukas Martinetz was awarded the prize for the best master thesis from the Faculty of Physics. The award certificate was presented by the Rector of the University of Duisburg-Essen, Prof. Ulrich Radtke, during the Dies Academicus ceremony.
May 11, 2018
Gas-induced friction and diffusion of classical rigid rotors
The impact of a rarefid gas on the coupled rotational and translational motion of arbitrarily shaped particles can be predicted microscopically from the Boltzmann equation, yielding the associated friction and diffusion tensors.
This article was designated as an Editor's Suggestion by Physical Review E.
December 7, 2017
Quantum Angular Momentum Diffusion of Nanoparticles
The rotational quantum dynamics of an arbitrarily shaped nanoparticle exhibits angular momentum diffusion due to the interaction with environmental gases and background fields.
New Journal of Physics 19 (2017) 122001 (Fast Track Communication)
This article was designated as Highlight 2017 by New Journal of Physics.
November 22, 2017
A nanoscale clock with precise dials
Suitably modulated laser beams imprint the precision of an electronic clock onto the intrinsically chaotic angular motion of a levitated nanoscale dial.
November 4, 2016
Kai Walter, Ph.D.
Habemus doctorem! Kai Walter received a Ph.D. from the Faculty of Physics for his dissertation on Coherence and Decoherence in High-mass Matter-wave Interferometry.
October 14, 2016
Rotranslational Cavity Cooling of Dielectric Rods and Disks
Nonspherical nanoparticles can be cooled to the quantum regime of their center-of-mass and rotational motion.Physical Review A 94, 033818 (2016)
October 10, 2016
Lutz Sörgel, Ph.D.
Habemus doctorem! Lutz Sörgel received a Ph.D. from the Faculty of Physics for his dissertation on Pointer state dynamics of dissipative quantum systems.
September 10, 2016
Björn Schrinski Receives Poster Award
Björn Schrinski presented his poster entitled Interference of Bose-Einstein Condensates under the Influence of Decoherence at the Conference Frontiers in Matter Wave Optics (FOMF2016) in Arcachon, France, and he received a poster award for his contribution.
July 4, 2016
Attending Bill Phillips' Master Class
Benjamin Stickler attended this year's Lindau Nobel Laureate Meeting at Lake Constance, and presented his research results in Bill Phillips' master class. Benjamin was also one of the few young researchers selected to present their work on a poster for all participants.
December 4, 2014
Stefan Nimmrichter receives Award of Excellence 2014
Stefan Nimmrichter was granted the Award of Excellence by the Federal Minister for Science, Research, and Commerce of the Republic of Austria.
September 2, 2014
Near-field interferometry of a free-falling nanoparticle from a point-like source
Our proposal for a near-field interference scheme for 106 amu silicon particles based on the single-source Talbot effect appeared in Nature Communications. It would allow testing the quantum superposition principle at unrivaled scales.
August 6, 2014
Felix Lucas, Ph.D.
Habemus doctorem! Felix Lucas received a Ph.D. from the Faculty of Physics for his dissertation on Adaptive Resummation of Markovian Quantum Dynamics.
August 5, 2014
Incoherent Control of the Retinal Isomerization
The back-action of quantum measurements can provide a handle for controling relatively complex quantum systems. This is demonstrated by means of an important bio-chemical reaction, the photo-induced isomerization of retinal in the protein rhodopsin.
Optomechanical sensing of spontaneous wave-function collapse
Hypothetical modifications of the Schrödinger equation, which serve to destroy superpositions on macroscopic scales, can be sensed by monitoring a test mass. Surprisingly, this mass should not be much greater than a few picogramms.
April 29, 2014
Timo Fischer, Ph.D.
Habemus doctorem! Timo Fischer received a Ph.D. from the Faculty of Physics for his dissertation Decoherence of the Orientation State.
April 1, 2014
Testing the limits of quantum mechanical superpositions
A review article on tests of the quantum superposition principle in increasingly macroscopic systems appeared in Nature Physics.
This is part of a dedicated issue, a Nature Physics Insight, on the foundations of quantum mechanics.
January 15, 2014
Adaptive Resummation of Markovian Quantum Dynamics
Our method for deriving analytic approximations for the dynamics of open quantum systems appeared in Physical Review Letters.
A more detailled article discusses the convergence properties and the numerical implementation of the resummation: Phys. Rev. A 89, 012112 (2014)
Dezember 30, 2013
Quantum mechanics in curved phase spaces
Our consistent extension of the Wigner-Weyl-Moyal phase-space formulation of quantum mechanics to general curved configuration spaces appeared in Physical Review A.
October 29, 2013
Stefan Nimmrichter, Ph.D.
Habemus doctorem! Stefan Nimmrichter received a Ph.D. from the University of Vienna for his dissertation on Macroscopic matter wave interferometry.
The work was awarded a Springer Thesis Prize,and it will be published as a Springer Thesis — 'Recognizing Outstanding Ph.D. Research'.
July 9, 2013
Nonlocal Young tests with Einstein-Podolsky-Rosen-correlated particle pairs
Nonlocal interference based on EPR-correlated particles allows one to detect entanglement and non-classical particle behavior using simple position measurements.
June 7, 2013
Wigner function for the orientation state
Our extension of the Wigner-Weyl phase space representation to the rotation dynamics of solid quantum objects appeared in New Journal of Physics.
April 18, 2013
Macroscopicity of mechanical quantum superposition states
Our proposal for an experimentally accessible, objective, and universal measure for the macroscopicity of superposition states in material quantum systems appeared in Physical Review Letters.
Feature articles on this work can be found in New Scientist (Quantum effects get a weirdness scale), in Physics World (How fat is Schrödinger’s cat?) and in Physics (Quantumness put on the scale). See also phys.org (Physicists propose measure of macroscopicity) und phsycs.com (Physicists introduce magnitude of macroscopicity).
May 12th - 17th, 2013
Summer school on tests of the quantum superposition principle
A summer school on Exploring the quantum superposition principle took place at the Physikzentrum Bad Honnef (near Bonn/Germany) on May 12th-17th, 2013. Further information is available at the school website.
Generous funding is provided by the Wilhem & Else Heraeus Foundation
February 7th, 2013
Kickoff meeting of NANOQUESTFIT collaboration
The kickoff meeting of the NANOQUESTFIT collaboration took place at Campus Duisburg, MG 465 on February 7th and 8th. A goal of this EU research project (ICT FET Open STREP) is to use matter wave interferometry of large molecules and clusters to probe the limits of the quantum superposition principle.