Generation of perfect-cavity-enhanced atom-photon entanglement with a millisecond lifetime via a spatially-multiplexed cavity

TL;DR

This paper demonstrates a multiplexed cavity system that significantly improves atom-photon entanglement efficiency and lifetime, enabling scalable quantum information processing with long-lived qubits.

Contribution

It introduces a multiplexed ring cavity with a polarization interferometer to eliminate cross readouts, achieving high-efficiency, long-lived entanglement.

Findings

50% intrinsic retrieval efficiency for 540 microsecond storage

13.5 times longer storage time than previous results

Avoids efficiency loss at all storage times

Abstract

A qubit memory is the building block for quantum information. Cavity-enhanced spin-wave-photon entanglement has been achieved by applying dual-control modes. However, owing to cross readouts between the modes, the qubit retrieval efficiency is about one quarter lower than that for a single spin-wave mode at all storage times. Here, we overcome cross readouts using a multiplexed ring cavity. The cavity is embedded with a polarization interferometer, and we create a write-out photonic qubit entangled with a magnetic-field-insensitive spin-wave qubit by applying a single-mode write-laser beam to cold atoms. The spin-wave qubit is retrieved with a single-mode read-laser beam, and the quarter retrieval-efficiency loss is avoided at all storage times. Our experiment demonstrates 50% intrinsic retrieval efficiency for 540 microsecond storage time, which is 13.5 times longer than the best reported result. Importantly, our multiplexed-cavity scheme paves one road to generate perfect-cavity-enhanced and large-scale multiplexed spin-wave-photon entanglement with a long lifetime.