Theoretical analysis on quantum interference effect in fast-light media

TL;DR

This paper provides a systematic theoretical analysis of quantum interference effects in various fast-light media, revealing conditions for stable superluminal signal propagation and potential applications in quantum information processing.

Contribution

It identifies the presence or absence of quantum interference in different gain-assisted atomic systems and explores how control field modulation affects these effects.

Findings

Fast-light media can eliminate absorption and suppress gain.

Quantum interference varies across different atomic configurations.

Control field modulation can switch interference effects.

Abstract

We make a systematic theoretical analysis on the quantum interference (QI) effects in various fast-light media (including gain-assisted $N$, gain-assisted ladder-I, and gain-assisted ladder-II atomic systems). We show that such fast-light media are capable of not only completely eliminating the absorption but also suppressing the gain of signal field, and hence provide the possibility to realize a stable propagation of the signal field with a superluminal velocity. We find that there is a destructive (constructive) QI effect in gain-assisted ladder-I (gain-assisted N) system, but no QI in the gain-assisted ladder-II system; furthermore, a crossover from destructive (constructive) QI to Autler-Townes splitting may occur for the gain-assisted ladder-I (gain-assisted N) system when the control field of the system is modulated. Our theoretical analysis can be applied to other multi-level systems, and the results obtained may have promising applications in optical and quantum information processing and transmission.