Decay, scattering, and decoherence in many-body quanum systems
Final Report Abstract
We studied various aspects of decay, scattering and decoherence in many-body quantum systems. The systems studied for this purpose comprise the helium atom (consisting of two interacting electrons) as well as interacting bosons in optical lattices, double well potentials or disordered potentials. Our general aim was to identify the signatures of interactions between these particles on the respective decay, scattering or decoherence processes. In total, our results can be summarized under the following five topics: (1) Decay of interacting many-body quantum systems: We studied, by means of numerically exact solution of the microscopic dynamics, the decay of two interacting particles in two different scenarios: (i) two interacting bosons in a double well, where we found that pairwise tunneling of the bosons may be realized for comparable widths of the two wells, whereas the decay process (corresponding to a broad initially unoccupied well) is dominated by uncorrelated single-particle decay, and (ii) ionization within a collinear model of microwave-driven doubly excited Rydberg helium atoms, where we proved that dynamical localization survives the impact of electron-electron interaction. (2) Probing Bose-Einstein condensates on lattices via scattering: The central purpose of this topic has been to probe Bose-Einstein condensates on lattices by a scattering particle without destroying the condensate. We showed that traces of the underlying classical mean-field phase space – which may be integrable (e.g. for lattices consisting of two wells) or chaotic (for more than two wells) manifest themselves in various, experimentally accessible scattering quantities such as the inelastic scattering cross section as a function of the energy of the incident probe particle. (3) Interaction-induced decoherence of Bose-Einstein condensates on optical lattices: In this part of our project, we investigated the dynamical evolution of ultracold bosons confined on a one-dimensional tilted optical lattice. Whereas, in the absence of interactions, the tilt induces periodic oscillations of the atoms on the lattice (‘Bloch oscillations’), we investigated the interaction-induced decay of these oscillations. We demonstrated that the associated decay rate undergoes a characteristic transition as the spectral structure of the Bose-Hubbard Hamiltonian changes from regular to chaotic. (4) Many-body quantum correlations: (i) We performed a theoretical study of the polarization entanglement of two photons emitted in the decay of metastable ionic states, showing in particular a reduction of entanglement for heavier ions due to relativistic effects. (ii) Furthermore, we investigated the creation of multi-photon entanglement via interference in linear optics setups. We developed a unifying framework providing a general representation of the states that can be created for bosons and fermions for any particle number and for any dimensionality of the entangled degree of freedom. (5) Interplay of disorder and interaction-induced nonlinearity: In the last topic, we studied multiple scattering of interacting quantum particles (i.e. bosonic atoms or photons) propagating in weakly disordered media. In particular, we developed a microscopic N-particle scattering theory that extends the stationary scattering theory of nonlinear bosonic matter waves in random potentials to the quantum many-particle regime beyond the mean field description. This theory allowed us to evaluate the impact of inelastic collisions on the coherently backscattered atomic flux density.
Publications
- Quantum dynamics in the bosonic Josephson junction, Phys. Rev. A 82, 053617 (2010)
Maya Chuchem, Katrina Smith-Mannschott, Moritz Hiller, Tsampikos Kottos, Amichay Vardi, Doron Cohen
(See online at https://doi.org/10.1103/PhysRevA.82.053617) - Scattering laser light on cold atoms: Toward multiple scattering signals from single-atom responses, Phys. Rev. A 82, 013832 (2010)
Thomas Wellens, Tobias Geiger, Vyacheslav Shatokhin, and Andreas Buchleitner
(See online at https://doi.org/10.1103/PhysRevA.82.013832) - Inelastic chaotic scattering on a Bose-Einstein condensate, J. Phys. B 45, 085302 (2012)
Stefan Hunn, Moritz Hiller, Doron Cohen, Tsampikos Kottos, and Andreas Buchleitner
(See online at https://doi.org/10.1088/0953-4075/45/8/085302) - Inelastic Multiple Scattering of Interacting Bosons in Weak Random Potentials, Phys. Rev. Lett. 109, 030601 (2012)
Tobias Geiger, Thomas Wellens, and Andreas Buchleitner
(See online at https://doi.org/10.1103/PhysRevLett.109.030601) - Unsharp continuous measurement of a Bose-Einstein condensate: Full quantum state estimation and the transition to classicality, Phys. Rev. A 86, 033624 (2012)
Moritz Hiller, Magnus Rehn, Francesco Petruccione, Andreas Buchleitner, and Thomas Konrad
(See online at https://doi.org/10.1103/PhysRevA.86.033624) - Weak disorder corrections of the scattering and transport mean free path, J. Phys. A 45, 395101 (2012)
Felix Eckert, Andreas Buchleitner, and Thomas Wellens
(See online at https://doi.org/10.1088/1751-8113/45/39/395101) - Limits to multipartite entanglement generation with bosons and fermions, Phys. Rev. A 87, 022319 (2013)
Malte C. Tichy, Florian Mintert, and Andreas Buchleitner
(See online at https://doi.org/10.1103/PhysRevA.87.022319) - Microscopic scattering theory for interacting bosons in weak random potentials, New J. Phys. 15, 115015 (2013)
Tobias Geiger, Andreas Buchleitner, and Thomas Wellens
(See online at https://doi.org/10.1088/1367-2630/15/11/115015) - Tunneling decay of two interacting bosons in an asymmetric double-well potential: A spectral approach, Phys. Rev. A 87, 043626 (2013)
Stefan Hunn, Klaus Zimmermann, Moritz Hiller, and Andreas Buchleitner
(See online at https://doi.org/10.1103/PhysRevA.87.043626)
