Dual-rail optical gradient echo memory

TL;DR

This paper presents a dual-rail optical gradient echo memory scheme that enables high-fidelity storage of frequency-separated signals in cold atoms, demonstrating promising results for quantum information processing.

Contribution

It introduces a novel dual-rail storage method using Zeeman-split Raman lines, enhancing the capability to store and manipulate frequency qubits in optical memories.

Findings

35% recall efficiency for dual-frequency pulses

82% interference fringe visibility

6 degrees phase stability

Abstract

We introduce a scheme for the parallel storage of frequency separated signals in an optical memory and demonstrate that this dual-rail storage is a suitable memory for high fidelity frequency qubits. The two signals are stored simultaneously in the Zeeman-split Raman absorption lines of a cold atom ensemble using gradient echo memory techniques. Analysis of the split-Zeeman storage shows that the memory can be configured to preserve the relative amplitude and phase of the frequency separated signals. In an experimental demonstration dual-frequency pulses are recalled with 35% efficiency, 82% interference fringe visibility, and 6 degrees phase stability. The fidelity of the frequency-qubit memory is limited by frequency-dependent polarisation rotation and ambient magnetic field fluctuations, our analysis describes how these can be addressed in an alternative configuration.