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Physica Scripta

Efficient light storage in modified superradiance lattice: overcoming the optical depth constraint

Atif Shabbir

Published Aug 14, 2026• 0 citations

Abstract

Abstract We propose an efficient light-storage scheme based on a modified superradiance lattice that achieves high storage efficiency with a significantly reduced dependence on optical depth (OD). Our results demonstrate storage efficiencies in the ranges of 25 % − 79 % , 66 % − 84 % , and 80 % − 86 % for ODs of 20, 156, and 500, respectively, under identical parameters with a fixed group delay of 10 μ s . Notably, the largest efficiency change is observed for the small OD of 20, highlighting the scheme’s robustness against variations in OD. Fidelity approaches near unity at optimized parameters, particularly at higher storage efficiency, i.e. greater than 80%. These results demonstrate that high-performance quantum memory can be realized without requiring excessively large ODs. Additionally, the difference in storage efficiency across ODs decreases with increasing group delay, making the scheme more independent of OD. The scheme also enables highly directional emission, improving experimental feasibility, and can be implemented using rubidium ( 87 Rb) atoms. Overall, this approach provides robust and scalable light storage, offering a promising platform for practical quantum memory and photonic information-processing applications.

DOI: 10.1088/1402-4896/ae9a0f

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Abstract We propose an efficient light-storage scheme based on a modified superradiance lattice that achieves high storage efficiency with a significantly reduced dependence on optical depth (OD). Our results demonstrate storage efficiencies in the ranges of 25 % − 79 % , 66 % − 84 % , and 80 % − 86 % for ODs of 20, 156, and 500, respectively, under identical parameters with a fixed group delay of 10 μ s . Notably, the largest efficiency change is observed for the small OD of 20, highlighting the scheme’s robustness against variations in OD. Fidelity approaches near unity at optimized parameters, particularly at higher storage efficiency, i.e. greater than 80%. These results demonstrate that high-performance quantum memory can be realized without requiring excessively large ODs. Additionally, the difference in storage efficiency across ODs decreases with increasing group delay, making the scheme more independent of OD. The scheme also enables highly directional emission, improving experimental feasibility, and can be implemented using rubidium ( 87 Rb) atoms. Overall, this approach provides robust and scalable light storage, offering a promising platform for practical quantum memory and photonic information-processing applications.

Abstract We propose modified superradiance lattice (MSL) based scheme to realize quantum memory where intensity of the control field plays an important role in achieving high storage efficiency. We report that via proposed scheme one can store light with 96% storage efficiency having corresponding fidelity of 99% and group delay 1 μs. We notice that the group delay can be enhanced to 10 μs via manipulation of the control field, however, the storage efficiency is reduced to 87%. The benefit of considering MSL for the quantum memory is that one can obtain directional light. The main advantage of the proposed scheme is that it does not require large optical depth to obtain high storage efficiency, which makes it experimentally more viable.

Quantum storage of flying optical qubits, namely coherently mapping photonic states into and out of an optically controlled memory on demand, constitutes an essential component in the optical quantum information processing science, with applications to long-distance optical communication [1]. In this context, practical protocols require sufficiently large storage efficiency to achieve a performance better than direct transmission. Theoretically, the storage and retrieval efficiency can only be improved with the increase of the optical depth (OD). Recent progresses have shown that high OD media enable to reach high-efficiency electromagnetically induced transparency (EIT)-based optical storage, albeit without the demonstration of qubit storage [2, 3]. Here we experimentally implement an optical quantum memory with single-photon-level probes, showing a EIT-based storage efficiency around 70%. Furthermore, thanks to the spatial multiplexing of the dense atomic ensemble, highly efficient storage of polarization qubit is performed.

A quantum memory with a high storage efficiency and a long coherence time is an essential element in quantum information applications. Here, we report our recent development of an optical quantum memory with a rubidium-87 cold atom ensemble. By increasing the optical depth of the medium, we have achieved a storage efficiency of 65% and a coherence time of 51 μs for a weak laser pulse. The result of a numerical analysis based on the Maxwell-Bloch equations agrees well with the experimental results. Our result paves the way toward an efficient optical quantum memory and may find applications in photonic quantum information processing.

The effects of high optical depth phenomena, such as superradiance, are investigated in potential quantum memory materials. The results may have relevance for several schemes, including controlled reversible inhomogeneous broadening, atomic frequency combs, and quantum memories based on electromagnetically induced transparency, which are based on using ensembles as storage media. It is shown that strong superradiant effects manifested as decay rates larger than $1/{T}_{2}^{\ensuremath{\ast}}$ are present even for moderate values of $\ensuremath{\alpha}L\ensuremath{\le}5$ and increases as a function of $\ensuremath{\alpha}L$. For even higher $\ensuremath{\alpha}L$, effects such as off-resonant slow light is demonstrated and discussed and, finally, the efficiency of time-reversed optimized input pulses is tested. A maximum retrieval efficiency of $\ensuremath{\sim}20%$ is reached and agreement with the theoretically expected result is discussed.

Quantum memory is an important component in the long-distance quantum communication system based on the quantum repeater protocol. To outperform the direct transmission of photons with quantum repeaters, it is crucial to develop quantum memories with high fidelity, high efficiency and a long storage time. Here, we achieve a storage efficiency of 96\% for a photonic memory based on the electromagnetically induced transparency (EIT) scheme in cold atomic media with an optical depth of near 1000. At a storage efficiency of 50\%, we also obtain a fractional delay of 1200. Both are the best record to date in all kinds of the schemes for the realization of quantum memory. Our work significantly advances the pursuit of a high-performance photonic memory and should have important applications in quantum information science.

We investigate optical memory efficiency and storage time across

^{85}\mathrm{Rb}

and

^{87}\mathrm{Rb}

isotopes on both the D

_1

and D

_2

transitions. Maximum efficiency of up to

44\%

was achieved using the D

_1

line in both isotopes, with up to 1.5 ms storage time. %Maximum efficiencies of

44\%

were measured for both isotopes on the D

_1

line, in agreement within

1σ

, while the longest storage time reached is

1.5

ms. These performance levels are enabled by warm vapor rubidium buffer-gas filled cells, large optical depth, and a near-resonant EIT scheme optimized with respect to the one- and two-photon detuning. Our results provide practical guidelines for optimizing the performance of warm rubidium vapor optical memories in simplified experimental configurations. We expect that the optimization approach employed here, specifically operating at elevated temperatures while identifying the optimal single-photon and two-photon detunings, should lead to improved performance of the quantum memory.