A Cavity-Enhanced Room-Temperature Broadband Raman Memory

TL;DR

This paper demonstrates a room-temperature broadband Raman quantum memory enhanced by a birefringent cavity, significantly reducing control energy and suppressing noise, achieving record low noise floor and high efficiency.

Contribution

It introduces a cavity-enhanced Raman memory that reduces energy requirements and noise, enabling more practical quantum memory implementations at room temperature.

Findings

Achieved the lowest unconditional noise floor in warm vapour Raman memory.

Demonstrated a total efficiency of approximately 9.5%.

Reduced control pulse energy significantly compared to previous implementations.

Abstract

Broadband quantum memories hold great promise as multiplexing elements in future photonic quantum information protocols. Alkali vapour Raman memories combine high-bandwidth storage, on-demand read-out, and operation at room temperature without collisional fluorescence noise. However, previous implementations have required large control pulse energies and suffered from four-wave mixing noise. Here we present a Raman memory where the storage interaction is enhanced by a low-finesse birefringent cavity tuned into simultaneous resonance with the signal and control fields, dramatically reducing the energy required to drive the memory. By engineering anti-resonance for the anti-Stokes field, we also suppress the four-wave mixing noise and report the lowest unconditional noise floor yet achieved in a Raman-type warm vapour memory, $(15\pm2)\times10^{-3}$ photons per pulse, with a total efficiency of $(9.5\pm0.5)$%.