Efficient quantum memory for heralded single photons generated by cavity-enhanced spontaneous parametric downconversion

TL;DR

This paper demonstrates a highly efficient, polarization-encoded quantum memory for heralded single photons generated by cavity-enhanced SPDC, achieving 70% efficiency and 97% fidelity, advancing quantum network development.

Contribution

It introduces a novel interface between cavity-enhanced SPDC and cold atomic ensembles for high-efficiency quantum memory of polarization qubits.

Findings

70% storage-and-retrieval efficiency achieved

Stored photons maintain non-classical properties after retrieval

Fidelity of polarization qubits reaches approximately 97%

Abstract

We interface a spontaneous parametric down conversion (SPDC) crystal and a cold atomic ensemble and demonstrate a highly efficient quantum memory through polarization-encoded single-photon qubits. Specifically, narrowband heralded single photons from a cavity-enhanced SPDC source is stored using cold atomic ensemble, with ~70% storage-and-retrieval efficiency and ~10$\mu$s storage time at 50% efficiency. To prevent the degradation after storage, we also manipulate the single-photon wave profile so that the retrieved non-classical nature of single photon is preserved. On the other hand, the dual-rail storage is used for storing polarization-encoded qubits, and the corrected fidelity of flying qubits after storage reaches ~97%. The results pave the way toward large-scale quantum network.