Scalable photonic network architecture based on motional averaging in room temperature gas

TL;DR

This paper introduces a scalable quantum memory and photon source architecture using motional averaging in room temperature atomic vapors, enabling long-lived quantum states and coherent photon production at ambient conditions.

Contribution

It develops a theoretical framework and demonstrates a proof-of-principle experiment for room temperature quantum memories based on motional averaging, overcoming previous limitations of atomic motion.

Findings

Long coherence times of scattered photons demonstrated

Efficient collective coupling achieved through motional averaging

Feasibility of scalable quantum memories at room temperature confirmed

Abstract

Quantum interfaces between photons and ensembles of atoms have emerged as powerful tools for quantum technologies. A major objective for such interfaces is high fidelity storage and retrieval of a photon in a collective quantum state of many atoms. This requires long-lived collective superposition states, which is typically achieved with immobilized atoms. Thermal atomic vapors, which present a simple and scalable resource, have, so far, only been used for continuous variable processing or for discrete variable processing on short time scales where atomic motion is negligible. We develop a theory based on the concept of motional averaging to enable room temperature discrete variable quantum memories and coherent single photon sources. We show that by choosing the interaction time so that atoms kept under spin protecting conditions can cross the light beam several times during the interaction combined with suitable spectral filtering, we erase the "which atom" information and obtain an efficient and homogenous coupling between all atoms and the light. Heralded single excitations can thus be created and stored as collective spinwaves, which can later be read out to produce coherent single photons in a scalable fashion. We demonstrate the feasibility of this approach to scalable quantum memories with a proof-of-principle experiment with room temperature atoms contained in microcells with spin protecting coating, placed inside an optical cavity. The experiment is performed at conditions corresponding to a few photons per pulse and clearly demonstrates a long coherence time of the forward scattered photons, which is the essential feature of the motional averaging.