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Quantum Computing, Communication, and Simulation

On-demand storage of telecom photons for a millisecond with spectro-temporal multiplexing

Anuj Sethia, Nasser Gohari Kamel, Daniel Oblak

Published Mar 5, 2026• 0 citations
Publisher

Abstract

The quantum internet is envisioned to enable transformative applications such as distributed quantum computing, quantum-enhanced distributed sensing, precise clock distribution, and secure communication. However, the development of the envisioned quantum internet hinges upon high performance quantum memories (QMs). Rare-earth ions doped in solids are among the promising candidates for realizing QMs due to high multimode storage capability, long coherence time and high storage efficiency. In this work, we demonstrate a practical solid-state memory using Erbium ions (Er3+), operating at telecom wavelengths (1536 nm) compatible with existing fiber-optic infrastructure. We showcase on-demand storage and retrieval of weak coherent pulses for up to 1 ms, the longest storage time using Er\textsuperscript{3+} reported in the literature. Crucially, our storage protocol operates without involving spin-level transitions, simplifying the system design and improving its robustness. We further showcase a temporal and spectral multimode capacity with selective recall capabilities, essential for a scalable quantum repeater architecture.

DOI
10.1117/12.3078332

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arXiv:2212.12898•Dec 25, 2022•1 citation
The quantum internet is envisioned to enable transformative applications such as distributed quantum computing, quantum-enhanced distributed sensing, precise clock distribution, and secure communication. However, the development of the envisioned quantum internet hinges upon high performance quantum memories (QMs). Rare-earth ions doped in solids are among the promising candidates for realizing QMs due to high multimode storage capability, long coherence time and high storage efficiency. In this work, we demonstrate a practical solid-state memory using Erbium ions (Er3+), operating at telecom wavelengths (1536 nm) compatible with existing fiber-optic infrastructure. We showcase on-demand storage and retrieval of weak coherent pulses for up to 1 ms, the longest storage time using Er\textsuperscript{3+} reported in the literature. Crucially, our storage protocol operates without involving spin-level transitions, simplifying the system design and improving its robustness. We further showcase a temporal and spectral multimode capacity with selective recall capabilities, essential for a scalable quantum repeater architecture.
The realization of scalable quantum networks for distribution of entanglement over long distances hinges on quantum repeaters. To outperform the exponential transmission loss in optical fibers, quantum repeaters must employ multiplexing schemes in the temporal, spectral, or spatial domain. The performance of such a multiplexed scheme is contingent on efficient quantum memories offering both extended storage times and large multimode capacities. Towards this goal, we experimentally demonstrate a memory platform operating at telecom wavelength using an Er3+^{3+}3+:Y2_{2}2​SiO5_{5}5​ crystal. We record on-demand storage and recall of weak coherent pulses for up to 111 ms, exceeding by an order of magnitude that of previously reported demonstrations based on Er3+^{3+}3+. The memory exhibits an efficiency of 10.36 % at 300 μμμs storage time with a signal-to-noise ratio of 10.910.910.9, mainly limited by spontaneous emission noise. We also store two spectral modes representing a frequency-bin encoding and retrieve the state with an overlap of 81.8 %. Furthermore, we demonstrate multimode capacity by simultaneously storing 20 temporal and 3 spectral modes with on-demand and selective recall capabilities, serving as a promising step toward a scalable quantum repeater architecture.
The faithful storage and coherent manipulation of quantum states with matter-systems would enable the realization of large-scale quantum networks based on quantum repeaters. To achieve useful communication rates, highly multimode quantum memories are required to construct a multiplexed quantum repeater. Here, we present a demonstration of on-demand storage of orbital-angular-momentum states with weak coherent pulses at the single-photon-level in a rare-earth-ion-doped crystal. Through the combination of this spatial degree-of-freedom (DOF) with temporal and spectral degrees of freedom, we create a multiple-DOF memory with high multimode capacity. This device can serve as a quantum mode converter with high fidelity, which is a fundamental requirement for the construction of a multiplexed quantum repeater. This device further enables essentially arbitrary spectral and temporal manipulations of spatial-qutrit-encoded photonic pulses in real time. Therefore, the developed quantum memory can serve as a building block for scalable photonic quantum information processing architectures.
Optical quantum memories operating directly at telecom wavelengths are a key enabling technology for long-distance quantum networks, yet on-demand storage onto long-lived ground-state spins in this spectral region has remained elusive due to the challenge of coherently transferring optical excitations to hyperfine spin states. Here we demonstrate spin-wave storage in 167^{167}167Er3+^{3+}3+:Y2_22​SiO5_55​ at 0.8 K and 1.1 T, establishing the core operational primitive required for on-demand telecom quantum memories. Using classical optical control pulses, we coherently transfer collective optical excitations to erbium hyperfine states with transfer efficiency exceeding 12%, enabling on-demand retrieval. We measure a hyperfine population lifetime of 25 s and demonstrate spin-wave storage for up to 25 μμμs. By identifying hyperfine inhomogeneous broadening as the dominant present limitation, our measurements define a clear pathway toward second-scale storage through improved spectral tailoring and dynamical decoupling. The results highlight the application of erbium-based solid-state memories for scalable fiber-compatible quantum repeater architectures.
Abstract To advance the full potential of quantum networks one should be able to distribute quantum resources over long distances at appreciable rates. As a consequence, all components in the networks need to have large multimode capacity to manipulate photonic quantum states. Towards this end, a multimode photonic quantum memory, especially one operating at telecom wavelength, remains a key challenge. Here we demonstrate a spectro-temporally multiplexed quantum memory at 1532 nm. Multimode quantum storage of telecom-band heralded single photons is realized by employing the atomic frequency comb protocol in a 10-m-long cryogenically cooled erbium doped silica fibre. The multiplexing encompasses five spectral channels - each 10 GHz wide - and in each of these up to 330 temporal modes, resulting in the simultaneous storage of 1650 modes of single photons. Our demonstrations open doors for high-rate quantum networks, which are essential for future quantum internet.
Photonic links between disparate quantum technologies−-−such as photon sources, memories, processors, clocks, and sensors−-−are key to scaling quantum networks and realizing a versatile quantum internet for secure quantum communication, distributed quantum computing, and entanglement-enhanced metrology. In practice, each technology is most suitably implemented on a different quantum platform; the substantial spectral mismatch between them, along with scarce native telecom interfaces, thus poses a major bottleneck to achieving efficient interconnections over long distances. Here we demonstrate the first deployed two-node hybrid network that operates entirely in the telecom C-band. Our approach uses no quantum frequency conversion or external filtering; instead, we develop a neutral atom single photon source and a solid-state rare-earth quantum memory that both operate in previously unexplored telecom regimes with state-of-the-art performance. The source achieves a high single-photon purity at 46 kcps, and the memory a storage efficiency of 10.6% with high multimode capacity. We leverage the intrinsic tunability of both systems to optimize their spectral overlap and demonstrate microsecond-level storage and retrieval with a large time-bandwidth product. Moreover, we showcase real-world networking competencies such as support for multiplexing across 37 temporal modes and preservation of non-classicality over fibers of 10.6 km (metropolitan) and 49.2 km (laboratory). Our work establishes a backbone for telecom-native quantum repeater links and unlocks a path towards high-bandwidth, large-scale quantum networking.
The quantum internet -- in synergy with the internet that we use today -- promises an enabling platform for next-generation information processing, including exponentially speed-up distributed computation, secure communication, and high-precision metrology. The key ingredients for realizing such a global network are the distribution and storage of quantum entanglement. As ground-based quantum networks are likely to be based on existing fiber networks, telecom-wavelength entangled photons and corresponding quantum memories are of central interest. Recently, 167Er3+\rm^{167}Er^{3+}167Er3+ ions have been identified as a promising candidate for an efficient, broadband quantum memory at telecom wavelength. However, to date, no storage of entangled photons, the crucial step of quantum memory using these promising ions, 167Er3+\rm^{167}Er^{3+}167Er3+, has been reported. Here, we demonstrate the storage and recall of the entangled state of two telecom photons generated from an integrated photonic chip based on a silicon nitride micro-ring resonator. Combining the natural narrow linewidth of the entangled photons and long storage time of 167Er3+\rm^{167}Er^{3+}167Er3+ ions, we achieve storage time of 1.936 μμμs, more than 387 times longer than in previous works. Successful storage of entanglement in the crystal is certified by a violation of an entanglement witness with more than 23 standard deviations (-0.234 ±\pm± 0.010) at 1.936 μμμs storage time. These results pave the way for realizing quantum networks based on solid-state devices.