Combined molecular dynamics and quantum trajectories simulation of laser-driven, collisional systems

TL;DR

This paper presents a combined molecular dynamics and quantum trajectories simulation to study laser-driven collisional systems, revealing how collisions influence quantum state evolution and laser cooling dynamics in ultracold plasmas.

Contribution

The authors develop a novel multiscale simulation method integrating MD and QT to analyze laser-driven collisional systems, capturing velocity-dependent quantum effects not described by traditional models.

Findings

Collisions suppress electromagnetically induced transparency.

Velocity changes affect quantum state evolution.

Thermalization occurs between cooled and uncooled directions.

Abstract

We introduce a combined molecular dynamics (MD) and quantum trajectories (QT) code to simulate the effects of near-resonant optical fields on state-vector evolution and particle motion in a collisional system. In contrast to collisionless systems, in which the quantum dynamics of multi-level, laser-driven particles with spontaneous emission can be described with the optical Bloch equations (OBEs), particle velocities in sufficiently collisional systems change on timescales comparable to those of the laser-induced, quantum-state dynamics. These transient velocity changes can cause the time-averaged velocity dependence of the quantum state to differ from the OBE solution. We use this multiscale code to describe laser-cooling in a strontium ultracold neutral plasma. Important phenomena described by the simulation include suppression of electromagnetically induced transparencies through rapid velocity changing collisions and thermalization between cooled and un-cooled directions for anisotropic laser cooling.