Quantum Interference of Stored Coherent Spin-wave Excitations in a Two-channel Memory

TL;DR

This paper demonstrates a two-channel quantum memory in a tripod atomic system that preserves quantum coherence and allows phase-controlled interference, advancing quantum information storage capabilities.

Contribution

It introduces a phase-sensitive two-channel quantum memory scheme that overcomes previous limitations in storing and manipulating dual spin-wave excitations.

Findings

Quantum coherence between stored spin-wave excitations confirmed.

Controlled interference (constructive/destructive) demonstrated.

Elimination of collapse and revival effects in readout signals.

Abstract

Quantum memories are essential elements in long-distance quantum networks and quantum computation. Significant advances have been achieved in demonstrating relative long-lived single-channel memory at single-photon level in cold atomic media. However, the qubit memory corresponding to store two-channel spin-wave excitations (SWEs) still faces challenges, including the limitations resulting from Larmor procession, fluctuating ambient magnetic field, and manipulation/measurement of the relative phase between the two channels. Here, we demonstrate a two-channel memory scheme in an ideal tripod atomic system, in which the total readout signal exhibits either constructive or destructive interference when the two-channel SWEs are retrieved by two reading beams with a controllable relative phase. Experimental result indicates quantum coherence between the stored SWEs. Based on such phase-sensitive storage/retrieval scheme, measurements of the relative phase between the two SWEs and Rabi oscillation, as well as elimination of the collapse and revival of the readout signal, are experimentally demonstrated.