Mainz 2017 – scientific programme

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A: Fachverband Atomphysik

A 7: Ultracold atoms and BEC - II (with Q)

A 7.4: Talk

Monday, March 6, 2017, 17:45–18:00, N 1

Realization of balanced gain and loss in a Bose-Hubbard model beyond the mean-field approximation — •Daniel Dizdarevic, Kirill Alpin, Johannes Reiff, Jörg Main, and Günter Wunner — 1. Institut für Theoretische Physik, Universität Stuttgart, Germany

In recent years there has been a growing interest in non-hermitian and especially PT symmetric quantum mechanics, since they allow for an effective description of open quantum systems. A quantum system exhibiting PT symmetry is given by a BEC in a double well with balanced particle gain and loss, which can be described in the mean-field limit by a Gross-Pitaevskii equation with a complex potential. Although a complex potential renders the Hamiltonian non-hermitian, PT-symmetric stationary states with real eigenvalue spectra exist.

We present a possible experimental realization of such a system by embedding it into a hermitian time-dependent four-mode optical lattice, where additional potential wells act as reservoirs and particle exchange happens via tunneling [1]. Since particle influx and outflux have to be controlled explicitly, a set of conditions on the potential parameters is derived. In contrast to previous work, our focus lies on a full many-particle description beyond the mean-field approximation using a Bose-Hubbard model, where especially the differences arising are of interest. Furthermore, we examine whether PT symmetric stationary states still appear in the limit of low particle numbers.

[1] Kreibich et al., Phys. Rev. A 87, 051601(R) (2013)