Decoherence-protected memory for a single-photon qubit

TL;DR

This paper demonstrates a single-atom-based photonic qubit memory with coherence times over 100 ms, surpassing previous limits and enabling long-distance quantum communication.

Contribution

It introduces a novel memory scheme that extends coherence time by mapping qubits between different bases, achieving over 100 ms coherence in a photonic qubit memory.

Findings

Coherence time exceeds 100 ms.

Storage-and-retrieval efficiency remains at 22%.

First photonic qubit memory surpassing the coherence time needed for quantum internet.

Abstract

The long-lived, efficient storage and retrieval of a qubit encoded on a photon is an important ingredient for future quantum networks. Although systems with intrinsically long coherence times have been demonstrated, the combination with an efficient light-matter interface remains an outstanding challenge. In fact, the coherence times of memories for photonic qubits are currently limited to a few milliseconds. Here we report on a qubit memory based on a single atom coupled to a high-finesse optical resonator. By mapping and remapping the qubit between a basis used for light-matter interfacing and a basis which is less susceptible to decoherence, a coherence time exceeding 100 ms has been measured with a time-independant storage-and-retrieval efficiency of 22%. This demonstrates the first photonic qubit memory with a coherence time that exceeds the lower bound needed for teleporting qubits in a global quantum internet.