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arXiv:2106.02530 · Physical Review Letters

Long-Lived Solid-State Optical Memory for High-Rate Quantum Repeaters

Mohsen Falamarzi Askarani, Antariksha Das, Jacob H. Davidson, Gustavo Castro do Amaral, Neil Sinclair, Joshua A. Slater, Sara Marzban, Charles W. Thiel, Rufus L. Cone, Daniel Oblak, Wolfgang Tittel

Published Nov 22, 2021• 53 citations
arXivHTMLPDF

Abstract

We argue that long optical storage times are required to establish entanglement at high rates over large distances using memory-based quantum repeaters. Triggered by this conclusion, we investigate the $795.325\text{ }\text{ }{\mathrm{nm}}^{3}$ ${\mathrm{H}}_{6}\ensuremath{\leftrightarrow}{^{3}\mathrm{H}}_{4}$ transition of $\mathrm{Tm}:{\mathrm{Y}}_{3}{\text{Ga}}_{5}{\mathrm{O}}_{12}$ (Tm:YGG). Most importantly, we find that the optical coherence time can reach 1.1 ms, and, using laser pulses, we demonstrate optical storage based on the atomic frequency comb protocol during up to $100\text{ }\text{ }\ensuremath{\mu}\mathrm{s}$ as well as a memory decay time ${T}_{m}$ of $13.1\text{ }\text{ }\ensuremath{\mu}\mathrm{s}$. Possibilities of how to narrow the gap between the measured value of ${T}_{m}$ and its maximum of $275\text{ }\text{ }\ensuremath{\mu}\mathrm{s}$ are discussed. In addition, we demonstrate multiplexed storage, including with feed-forward selection, shifting and filtering of spectral modes, as well as quantum state storage using members of nonclassical photon pairs. Our results show the potential of Tm:YGG for creating multiplexed quantum memories with long optical storage times, and open the path to repeater-based quantum networks with high entanglement distribution rates.

DOI
10.1103/physrevlett.127.220502

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We argue that long optical storage times are required to establish entanglement at high rates over large distances using memory-based quantum repeaters. Triggered by this conclusion, we investigate the 795.325  nm3795.325\text{ }\text{ }{\mathrm{nm}}^{3}795.325  nm3 H6\ensuremath↔3H4{\mathrm{H}}_{6}\ensuremath{\leftrightarrow}{^{3}\mathrm{H}}_{4}H6​\ensuremath↔3H4​ transition of Tm:Y3Ga5O12\mathrm{Tm}:{\mathrm{Y}}_{3}{\text{Ga}}_{5}{\mathrm{O}}_{12}Tm:Y3​Ga5​O12​ (Tm:YGG). Most importantly, we find that the optical coherence time can reach 1.1 ms, and, using laser pulses, we demonstrate optical storage based on the atomic frequency comb protocol during up to 100  \ensuremathμs100\text{ }\text{ }\ensuremath{\mu}\mathrm{s}100  \ensuremathμs as well as a memory decay time Tm{T}_{m}Tm​ of 13.1  \ensuremathμs13.1\text{ }\text{ }\ensuremath{\mu}\mathrm{s}13.1  \ensuremathμs. Possibilities of how to narrow the gap between the measured value of Tm{T}_{m}Tm​ and its maximum of 275  \ensuremathμs275\text{ }\text{ }\ensuremath{\mu}\mathrm{s}275  \ensuremathμs are discussed. In addition, we demonstrate multiplexed storage, including with feed-forward selection, shifting and filtering of spectral modes, as well as quantum state storage using members of nonclassical photon pairs. Our results show the potential of Tm:YGG for creating multiplexed quantum memories with long optical storage times, and open the path to repeater-based quantum networks with high entanglement distribution rates.
Long optical storage times are an essential requirement to establish high-rate entanglement distribution over large distances using memory-based quantum repeaters. Rare earth ion-doped crystals are arguably well-suited candidates for building such quantum memories. Toward this end, we investigate the 795.32 nm 3H6 ↔ 3H4 transition of 1% thulium-doped yttrium gallium garnet crystal (Tm3+:Y3Ga5O12 : Tm3+:YGG). Most essentially, we find that the optical coherence time can reach 1.1 ms, and, using laser pulses, we demonstrate optical storage based on the atomic frequency comb (AFC) protocol up to 100 µs. In addition, we demonstrate multiplexed storage, including feed-forward selection, shifting, and filtering of spectral modes, as well as quantum state storage using members of non-classical photon pairs. Our results show that Tm:YGG can be a potential candidate for creating multiplexed quantum memories with long optical storage times.
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Photon loss in optical fibers prevents long-distance distribution of quantum information on the ground. Quantum repeater is proposed to overcome this problem, but the communication distance is still limited so far because of the system complexity of the quantum repeater scheme. Alternative solutions include transportable quantum memory and quantum-memory-equipped satellites, where long-lived optical quantum memories are the key components to realize global quantum communication. However, the longest storage time of the optical memories demonstrated so far is approximately 1 minute. Here, by employing a zero-first-order-Zeeman magnetic field and dynamical decoupling to protect the spin coherence in a solid, we demonstrate coherent storage of light in an atomic frequency comb memory over 1 hour, leading to a promising future for large-scale quantum communication based on long-lived solid-state quantum memories.
Abstract Photon loss in optical fibers prevents long-distance distribution of quantum information on the ground. Quantum repeater is proposed to overcome this problem, but the communication distance is still limited so far because of the system complexity of the quantum repeater scheme. Alternative solutions include transportable quantum memory and quantum-memory-equipped satellites, where long-lived optical quantum memories are the key components to realize global quantum communication. However, the longest storage time of the optical memories demonstrated so far is approximately 1 minute. Here, by employing a zero-first-order-Zeeman magnetic field and dynamical decoupling to protect the spin coherence in a solid, we demonstrate coherent storage of light in an atomic frequency comb memory over 1 hour, leading to a promising future for large-scale quantum communication based on long-lived solid-state quantum memories.
Future multiphoton applications of quantum optics and quantum information science require quantum memories that simultaneously store many photon states, each encoded into a different optical mode, and enable one to select the mapping between any input and a specific retrieved mode during storage. Here we show, with the example of a quantum repeater, how to employ spectrally multiplexed states and memories with fixed storage times that allow such mapping between spectral modes. Furthermore, using a Ti:Tm:LiNbO_{3} waveguide cooled to 3 K, a phase modulator, and a spectral filter, we demonstrate storage followed by the required feed-forward-controlled frequency manipulation with time-bin qubits encoded into up to 26 multiplexed spectral modes and 97% fidelity.