Quantum fluctuation effects on the quench dynamics of thermal quasicondensates

TL;DR

This paper investigates how quantum fluctuations affect the dynamics of a trapped quasicondensate after an interaction quench, using a novel quantum-inclusive stochastic approach that combines quantum and thermal effects.

Contribution

The authors develop a quantum-enhanced stochastic Gross-Pitaevskii equation using the positive-P representation to include quantum fluctuations in quench dynamics analysis.

Findings

Observation of antibunching effects.

Generation of counter-propagating atom pairs.

Enhanced phase fluctuations after quench.

Abstract

We study the influence of quantum fluctuations on the phase, density, and pair correlations in a trapped quasicondensate after a quench of the interaction strength. To do so, we derive a description similar to the stochastic Gross-Pitaevskii equation (SGPE) but keeping a fully quantum description of the low-energy fields using the positive-P representation. This allows us to treat both the quantum and thermal fluctuations together in an integrated way. A plain SGPE only allows for thermal fluctuations. The approach is applicable to such situations as finite temperature quantum quenches, but not equilibrium calculations due to the time limitations inherent in positive-P descriptions of interacting gases. One sees the appearance antibunching, the generation of counter-propagating atom pairs, and increased phase fluctuations. We show that the behavior can be estimated by adding the T=0 quantum fluctuation contribution to the thermal fluctuations described by the plain SGPE.