Superradiant Emission of Ultra-Bright Photon Pairs in Doppler-Broadened Atomic Ensemble

TL;DR

This paper demonstrates superradiant emission of ultra-bright photon pairs in a Doppler-broadened atomic ensemble, highlighting enhanced photon generation rates and the observation of superradiant beating, advancing quantum communication technologies.

Contribution

It reports the first observation of superradiant beating in a Doppler-broadened atomic system and achieves ultra-bright photon pair generation via superradiance in thermal vapor.

Findings

Photon pair rate of 64,600 cps/mW achieved.

Quadratic relation between heralded photon probability and optical depth.

First observation of superradiant beating at high optical depth.

Abstract

With a recent rising interest of single photon superradiance due to its potential usefulness for efficient collection of single photon from an atomic ensemble, bright and narrow photon pair source is a key component in realization of quantum communication and quantum computer based on coherent interaction between light and atomic ensemble. We report the superradiant emission of ultra-bright photon pairs with a coincidence counting rate per input power of 64,600 cps/mW via spontaneous four-wave mixing in a thermal vapour cell. The photon-pair generation rate is enhanced by the contribution of two-photon coherence of almost atomic velocity groups in the Doppler-broadened ladder-type atomic system. The quadratic proportionality of the probability of detecting a heralded single photon as a function of the optical depth clarifies that the ultra-brightness results from the superradiance. In addition, a single photon superradiant beating at a high optical depth of the atomic ensemble is observed for the first time.