Vacuum-Induced Transparency

TL;DR

This paper demonstrates vacuum-induced transparency in a cold atom ensemble coupled to an optical cavity, enabling control of light transmission and delay at the few-photon level, with potential applications in quantum information processing.

Contribution

The experiment shows that the electromagnetic vacuum can induce transparency and control light propagation in a strongly coupled atom-cavity system, a novel quantum nonlinear effect.

Findings

Vacuum induces a 25 ns group delay on optical pulses.

Transparency increases from 40% to 80% with 10 photons in the cavity.

The effect enables photon-number-state filtering for quantum devices.

Abstract

Photons are excellent information carriers but normally pass through each other without consequence. Engineered interactions between photons would enable applications from quantum information processing to simulation of condensed matter systems. Using an ensemble of cold atoms strongly coupled to an optical cavity, we demonstrate experimentally that the transmission of light through a medium may be controlled with few photons and even by the electromagnetic vacuum field. The vacuum induces a group delay of 25 ns on the input optical pulse, corresponding to a light velocity of 1600 m/s, and a transparency of 40% that increases to 80% when the resonator is filled with 10 photons. This strongly nonlinear effect provides prospects for advanced quantum devices such as photon-number-state filters.