Efficient cavity-assisted storage of photonic qubits in a solid-state quantum memory

TL;DR

This paper demonstrates highly efficient storage and retrieval of photonic qubits in a solid-state quantum memory using a cavity-enhanced atomic frequency comb, achieving record efficiencies and fidelity for quantum information storage.

Contribution

The work introduces a cavity-enhanced AFC quantum memory in a solid-state crystal with record storage efficiency and fidelity for photonic qubits at the single-photon level.

Findings

Achieved up to 62% efficiency for single-photon level pulse storage.

Stored time-bin qubits with over 51% efficiency and 94.8% fidelity.

Extended storage times up to 70 microseconds with impedance matching.

Abstract

We report on the high-efficiency storage and retrieval of weak coherent optical pulses and photonic qubits in a cavity-enhanced solid-state quantum memory. By using an atomic frequency comb (AFC) memory in a $Pr^{3+}:Y_2 SO_5$ crystal embedded in a low-finesse impedance-matched cavity, we stored weak coherent pulses at the single photon level with up to 62% efficiency for a pre-determined storage time of 2 $\mu$s. We also confirmed that the impedance-matched cavity enhances the efficiency for longer storage times up to 70 $\mu$s. Taking advantage of the temporal multimodality of the AFC scheme, we then store weak coherent time-bin qubits with (51+-2)% efficiency and a measurement-device limited fidelity over (94.8+-1.4)% for the retrieved qubits. These results represent the most efficient storage in a single photon level AFC memory and the most efficient qubit storage in a solid-state quantum memory up-to-date.