Quantum Storage of Frequency-Multiplexed Photons Exhibiting Nonclassical Correlations with Telecom C-Band Photons

TL;DR

This paper demonstrates the integration of a cavity-enhanced photon-pair source with a broadband quantum memory, achieving high-frequency multiplexing and preserving nonclassical correlations, advancing scalable quantum communication networks.

Contribution

It presents the first integration of a cavity-enhanced telecom-band photon source with a rare-earth-ion-doped quantum memory for high-frequency multiplexing.

Findings

Up to 83 frequency modes stored in the quantum memory.

Maintained strong nonclassical correlations after storage.

Achieved broadband storage of 606 nm photons with high spectral multiplexing.

Abstract

Multiplexing is essential for improving entanglement distribution rates in quantum communication. Frequency multiplexing provides a promising and scalable path toward large-capacity quantum networks. Further progress requires increasing the number of frequency modes and developing broadband photon-pair sources and quantum memories that are spectrally compatible. Here, we report the integration of a cavity-enhanced spontaneous parametric down-conversion source in the telecom C-band with a frequency-multiplexed atomic frequency comb memory. The bow-tie cavity source was simultaneously resonant at 606 nm and 1550 nm, generating non-degenerate photon pairs exhibiting a clustered frequency-comb spectrum. The atomic frequency comb memory, implemented in Praseodymium-doped Yttrium Orthosilicate crystals, provided up to 83 frequency modes with 123 MHz spacing and enabled broadband storage of 606 nm signal photons. By filtering the main cluster, we obtained $32.7 \pm 4.8$ effective modes, as confirmed from coincidence measurements. Importantly, we observed strong nonclassical correlations after storage, with cross-correlation values of $g_{s,i}^{(2)} = 8.1\pm0.7$. Our experimental results demonstrate the feasibility of integrating cavity-enhanced photon-pair sources with rare-earth-ion-doped solid-state memories. The integration reveals a high frequency multiplicity that is essential for scalable quantum networks.