Multimode Raman light-atom interface in warm atomic ensemble as multiple three-mode quantum operations

TL;DR

This paper investigates a multimode Raman light-atom interface in warm atomic ensembles, revealing its potential for quantum memory and entanglement generation through a universal multimode transformation model.

Contribution

It introduces a comprehensive model of multimode Raman interactions in warm atoms, including both Stokes and anti-Stokes processes, with a mode basis analysis and practical implications.

Findings

Modes are coupled via a transformation combining beamsplitters and two-mode squeezing.

The model applies to warm rubidium-87 vapor, bridging Stokes-only and anti-Stokes-only regimes.

Provides a universal description for multimode quantum state evolution in warm atomic ensembles.

Abstract

We analyze the properties of a Raman quantum light-atom interface in long atomic ensemble and its applications as a quantum memory or two-mode squeezed state generator. We consider the weak-coupling regime and include both Stokes and anti-Stokes scattering and the effects of Doppler broadening in buffer gas assuming frequent velocity-averaging collisions. We find the Green functions describing multimode transformation from input to output fields of photons and atomic excitations. Proper mode basis is found via singular value decomposition for short interaction times. It reveals that triples of modes are coupled by a transformation equivalent to a combination of two beamsplitters and a two-mode squeezing operation. We analyze the possible transformations on an example of warm rubidium-87 vapor. The model we present bridges the gap between the Stokes only and anti-Stokes only interactions providing simple, universal description in a temporally and longitudinally multimode situation. Our results also provide an easy way to find an evolution of the states in a Schr\"odinger picture thus facilitating understanding and design.