Cavity-assisted squeezing and entanglement: Non-adiabatic effects and optimal cavity-atomic ensemble matching

TL;DR

This paper explores how increasing cavity field lifetime and optimizing cavity-atomic ensemble matching can enhance quantum entanglement and control in cavity-assisted Raman schemes, especially beyond the bad cavity limit, considering non-adiabatic effects.

Contribution

It introduces methods to optimize cavity and atomic ensemble parameters for improved entanglement and control in non-adiabatic regimes, extending beyond traditional bad cavity assumptions.

Findings

Optimal control field profiles enable predefined output signal shapes.

Enhanced light-matter coupling reduces the need for intense control fields.

Proper cavity-ensemble matching minimizes nonlinear effects and improves entanglement.

Abstract

We investigate theoretically quantum entanglement of light with the collective spin polarization of a cold atomic ensemble in cavity-assisted Raman schemes. Previous works concentrated mostly on the bad cavity limit where the signals are much longer than the cavity field lifetime. In view of atomic relaxation and other imperfections, there may arise a need to speed-up the light-atoms interface operation. By increasing the cavity field lifetime, one can achieve better light-matter coupling and entanglement. In our work, we consider the non-adiabatic effects that become important beyond the bad cavity limit in both low-photon and continuous variables regime. We find classical control field time profiles that allow one to retrieve from the cavity an output quantized signal of a predefined time shape and duration, which is optimal for the homodyne detection, optical mixing or further manipulation. This is done for a wide range of the signal duration as compared to the cavity field lifetime. We discuss an optimal cavity-atomic ensemble matching in terms of the cavity field lifetime which allows one to apply less intense control field and to minimize a variety of non-linear effects, such as AC light shifts, four-wave mixing, etc, which may be potentially harmful to an experiment.