Subnatural-linewidth biphotons from a Doppler-broadened hot atomic vapor cell

TL;DR

This paper demonstrates an efficient method to generate narrowband biphotons with subnatural linewidth from a hot atomic vapor cell, enabling potential applications in quantum communication and quantum information processing.

Contribution

The authors introduce a backward phase-matching scheme with optical pumping to produce subnatural-linewidth biphotons from a Doppler-broadened hot atomic vapor, improving spectral purity and controllability.

Findings

Achieved biphotons with linewidth less than 6 MHz.

Controlled bandwidth and coherence time of photon pairs.

Minimized uncorrelated photons via backward phase-matching.

Abstract

We report the efficient generation of subnatural-linewidth (< 6 MHz, for Rb D1/D2 lines) biphotons from a Doppler-broadened (530 MHz) hot atomic vapor cell. We use on-resonance spontaneous four-wave mixing in a hot paraffin-coated 87Rb vapor cell at 63 C to produce time-frequency entangled photon pairs with controllable bandwidth (1.9 - 3.2 MHz) and coherence time (47 - 94 ns). Our backward phase-matching scheme with optical pumping is the key to minimize the generation of uncorrelated photons from resonance fluorescence. The result paves the way toward miniature narrowband biphoton source based on atomic cells