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Journal of Experimental and Theoretical Physics Letters

Quantum Memory Based on a Eu:YSO Crystal: the Storage and Retrieval of Single-Photon States Generated via Spontaneous Parametric Down-Conversion

Ахмеджанов Ринат Абдулхаевич, Л. А. Гущин, I. V. Zelensky, А. А. Калачев, Латыпов Ильнур Зиннурович, В. А. Низов, Н. А. Низов, D. A. Sobgayda, D. A. Turaykhanov, N. M. Shafeev, А. В. Шкаликов

Published Nov 1, 2025• 0 citations
Publisher

Abstract

The storage of single photons generated via nondegenerate spontaneous parametric down-conversion in a cavity with a PPKTP crystal in quantum memory based on an atomic frequency comb in a Eu:YSO crystal is demonstrated. A technique for preparing spectral profiles within the absorption line of a doped crystal that are matched to the spectrum of single-photon radiation is developed. For storage times of 250 and 166 ns, quantum memory efficiencies of 3 and 7% have been obtained with signal-to-noise ratios of 1/4 and 1/2, respectively.

DOI
10.1134/s0021364025609376

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EPJ Web of Conferences•Jan 1, 2017•1 citation
The storage of single photons generated via nondegenerate spontaneous parametric down-conversion in a cavity with a PPKTP crystal in quantum memory based on an atomic frequency comb in a Eu:YSO crystal is demonstrated. A technique for preparing spectral profiles within the absorption line of a doped crystal that are matched to the spectrum of single-photon radiation is developed. For storage times of 250 and 166 ns, quantum memory efficiencies of 3 and 7% have been obtained with signal-to-noise ratios of 1/4 and 1/2, respectively.
The storage of a signal of a single-photon source based on spontaneous parametric down-conversion in a periodically poled MgO:PPLN crystal in a quantum memory based on an atomic frequency comb in an isotopically pure 143Nd:Y7LiF4^{{{\text{143}}}}{\text{Nd}}{\kern 1pt} {\text{:}}{\kern 1pt} {{{\text{Y}}}^{{\text{7}}}}{\text{Li}}{{{\text{F}}}_{{\text{4}}}}143Nd:Y7LiF4​ crystal has been demonstrated.
In an isotopically pure 143Nd3+:Y7LiF4 crystal we demonstrate an optical quantum memory on a single photon level using the atomic frequency comb memory protocol. Using weakened laser pulses we demonstrate storage efficiency of 6.5% with the storage time of ∼ \sim ∼ 60 ns and signal to noise ratio of around 3.
A light-storage experiment with a total (storage and retrieval) efficiency η=56% is carried out by enclosing a sample, with a single-pass absorption of 10%, in an impedance-matched cavity. The experiment is carried out using the atomic frequency comb (AFC) technique in a praseodymium-doped crystal (0.05%Pr(3+):Y2SiO5) and the cavity is created by depositing reflection coatings directly onto the crystal surfaces. The AFC technique has previously by far demonstrated the highest multimode capacity of all quantum memory concepts tested experimentally. We claim that the present work shows that it is realistic to create efficient, on-demand, long storage time AFC memories.
Rare-earth-ion doped crystals are state-of-the-art materials for optical quantum memories and quantum transducers between optical and microwave photons. Here we describe our progress towards a nanophotonic quantum memory based on a rare-earth (Neodymium) doped yttrium orthosilicate (YSO) photonic crystal resonator. The Purcell-enhanced coupling of the 883 nm transitions of Neodymium (Nd3+) ions to the nano-resonator results in increased optical depth, which could in principle facilitate highly efficient photon storage via cavity impedance matching. The atomic frequency comb (AFC) memory protocol can be implemented in the Nd:YSO nano-resonator by efficient optical pumping into the long-lived Zeeman state. Coherent optical signals can be stored and retrieved from the AFC memory. We currently measure a storage efficiency on par with a bulk crystal Nd:YSO memory that is millimeters long. Our results will enable multiplexed on-chip quantum storage and thus quantum repeater devices using rare-earth-ions.
We report on the realization of an efficient solid-state spin-wave quantum memory, with on-demand readout, using the full atomic frequency comb (AFC) scheme in a Pr^{3+}:Y_{2}SiO_{5} crystal embedded in an impedance-matched cavity. We demonstrate operation at the single-photon level by storing weak coherent states with an efficiency up to (40±2)% and a signal-to-noise ratio of 14 for an input photon number of 0.42 photons per pulse. We also investigated the enhancement of the incoherent noise due to the impedance-matched cavity and characterized the quantum memory performance, showing a two-way transfer from excited to spin states and back of up to 83%. Finally, we confirmed the quantum nature of our memory by storing nonclassical states of light, i.e., a heralded single photon from a nondegenerate spontaneous parametric down-conversion source, and achieved nonclassical correlations between the heralding and the stored-and-retrieved photon. These results demonstrate that impedance-matched AFC spin-wave quantum memories with on-demand readout can be used for experiments involving the storage of photonic quantum states. They also open the door to solid-state on-demand quantum memories with very high efficiencies, serving as a key resource for quantum networks and quantum repeaters.
We report on the realization of a tunable single-photon source compatible with quantum memories based on isotopically pure Y7LiF4 crystals doped with Nd3+ ions. The source is based on spontaneous parametric down-conversion in a PPLN crystal placed in a resonator. The latter is formed by two mirrors which are transparent for the pump (532 nm) and idler (1377 nm) fields but high reflective for the signal field (867 nm). The width of the second-order cross-correlation function between the signal and idler photons is determined to be 1.5 ns for the cavity length of 8 cm, which corresponds to a cavity bandwidth of 100 MHz.