The Duan-Kimble cavity-atom quantum memory loading scheme revisited

TL;DR

This paper revisits and corrects the Duan-Kimble quantum memory loading scheme, introduces an improved push-pull configuration, and analyzes its performance to optimize quantum repeater protocols.

Contribution

It corrects a key error in the original scheme and proposes a new tuning method that enhances memory fidelity and loading rate.

Findings

The corrected analytical solution clarifies the phase shift behavior.

The push-pull configuration outperforms the original in fidelity and rate.

Performance metrics guide future quantum repeater optimization.

Abstract

We reexamine the well-known Duan-Kimble entanglement scheme, wherein the state of a single-photon qubit is entangled with a quantum memory consisting of a single-atom qubit in a strongly coupled optical cavity, providing the capability to load the photon's state into the memory. We correct a common error appearing in some subsequent papers regarding the validity of the single-photon reflectivity function that characterizes the essential phase shift at the heart of the protocol. Using the validated analytical solution, we introduce an improved scheme-the push-pull configuration-where the photon and cavity are tuned at the midpoint between atomic resonances and show that it can outperform the original on-off configuration in which the photon and cavity are tuned exactly to one of the atomic resonances. The performance metric used is the final memory-state fidelity versus the heralding probability, which determines the memory loading rate. The results should play a role in optimizing future quantum repeater schemes based on the Duan-Kimble protocol.