Diffusion induced decoherence of stored optical vortices

TL;DR

This paper investigates how thermal diffusion affects the coherence of stored optical vortices in atomic ensembles, revealing unexpected decoherence behavior and implications for quantum information storage.

Contribution

It demonstrates that stored optical vortices can decohere faster than Gaussian modes under diffusion, challenging assumptions about their robustness in quantum memory applications.

Findings

Stored vortex coherence is more fragile than Gaussian modes under diffusion.

The vortex center becomes incoherent and shows nonzero intensity upon readout.

Less phase gradient in vortices correlates with increased robustness against diffusion.

Abstract

We study the coherence properties of optical vortices stored in atomic ensembles. In the presence of thermal diffusion, the topological nature of stored optical vortices is found not to guarantee slow decoherence. Instead the stored vortex state has decoherence surprisingly larger than the stored Gaussian mode. Generally, the less phase gradient, the more robust for stored coherence against diffusion. Furthermore, calculation of coherence factor shows that the center of stored vortex becomes completely incoherent once diffusion begins and, when reading laser is applied, the optical intensity at the center of the vortex becomes nonzero. Its implication for quantum information is discussed. Comparison of classical diffusion and quantum diffusion is also presented.