Simulating quantum transport for a quasi-one-dimensional Bose gas in an optical lattice: the choice of fluctuation modes in the truncated Wigner approximation

TL;DR

This study investigates how different basis sets for initial quantum fluctuations affect the simulated dynamics of a quasi-one-dimensional Bose gas in an optical lattice, revealing significant differences in transport properties and coherence.

Contribution

It compares the effects of plane-wave, harmonic-oscillator, and Bogoliubov modes in the truncated Wigner approximation for quantum fluctuation modeling.

Findings

SCB modes predict greater phase decoherence and number fluctuations.

PW modes overestimate atom expulsion from the cloud core.

Other modes align better with experimental observations.

Abstract

We study the effect of quantum fluctuations on the dynamics of a quasi-one-dimensional Bose gas in an optical lattice at zero-temperature using the truncated Wigner approximation with a variety of basis sets for the initial fluctuation modes. The initial spatial distributions of the quantum fluctuations are very different when using a limited number of plane-wave (PW), simple-harmonic-oscillator (SHO) and self-consistently determined Bogoliubov (SCB) modes. The short-time transport properties of the Bose gas, characterized by the phase coherence in the PW basis are distinct from those gained using the SHO and SCB basis. The calculations using the SCB modes predict greater phase decoherence and stronger number fluctuations than the other choices. Furthermore, we observe that the use of PW modes overestimates the extent to which atoms are expelled from the core of the cloud, while the use of the other modes only breaks the cloud structure slightly which is in agreement with the experimental observations [1].