Darkness of two-mode squeezed light in {\Lambda}-type atomic system

TL;DR

This paper demonstrates that two-mode squeezed vacuum states can propagate through a lossy {\

Contribution

It introduces a mechanism in {\

Findings

TMSV states can be preserved in lossy atomic media.

Losses can generate TMSV states from other inputs.

Theoretical predictions align with recent experiments.

Abstract

We show that, under certain circumstances, an optical field in a two-mode squeezed vacuum (TMSV) state can propagate through a lossy atomic medium without degradation or evolution. Moreover, the losses give rise to that state when a different state is initially injected into the medium. Such a situation emerges in a {\Lambda}-type atomic system, in which both optical transitions are driven by strong laser fields that are two-photon resonant with the respective signal modes. Then the interactions of the two signal modes with the ground-state atomic coherence interfere destructively, thereby ensuring the preservation of the TMSV with a particular squeezing parameter. This mechanism permits unified interpretation of recent experimental results and predicts new phenomena.