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Open quantum system theory for Bose polarons in a trapped Bose-Einstein condensate

Research paper by Aniello Lampo, Christos Charalambous, Miguel Ángel García-March, Maciej Lewenstein

Indexed on: 23 Mar '18Published on: 23 Mar '18Published in: arXiv - Condensed Matter - Quantum Gases



Abstract

We study the dynamics of an impurity embedded in a trapped Bose-Einstein condensate, i.e. the Bose polaron problem, with the open quantum systems techniques. In this framework, the impurity corresponds to a particle performing quantum Brownian motion, and the excitation modes of the Bose-Einstein condensate play the role of the environment. We solve the associated quantum Langevin equation to find the position and momentum variances of the impurity. When the impurity is untrapped, its long-time dynamics is super-diffusive. When the impurity is trapped, we find position squeezing. To consider a Bose-Einstein condensate in a trapping potential is crucial to study this system in experimental realistic conditions. We detail how, for the untrapped case, the diffusion coefficient, which is a measurable quantity, depends on the Bose-Einstein condensate trap frequency. Also, we show that, for the trapped case, the squeezing can be enhanced or inhibited by tuning the Bose-Einstein condensate trap frequency.