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arXiv:2402.14686

Room-temperature ladder-type optical memory compatible with single photons from InGaAs quantum dots

Benjamin Maaß, Norman Vincenz Ewald, Avijit Barua, Stephan Reitzenstein, Janik Wolters

Published Feb 22, 2024• 0 citations
arXivHTMLPDF

Abstract

On-demand storage and retrieval of quantum information in coherent light-matter interfaces is a key requirement for future quantum networking and quantum communication applications. Alkali vapor memories offer scalable and robust high-bandwidth storage at high repetition rates which makes them a natural fit to interface with solid-state single-photon sources. Here, we experimentally realize a room-temperature ladder-type atomic vapor memory that operates on the Cs D1 line. We provide a detailed experimental characterization and demonstration of on-demand storage and retrieval of weak coherent laser pulses with 0.06 photons per pulse at a high signal-to-noise ratio of SNR$=830(80)$. The memory achieves a maximum internal storage efficiency of $η_{\text{int}}=15(1)\%$ and an estimated $1/e$-storage time of $τ_{\mathrm{s}}\approx32\,$ns. Benchmark properties for the storage of single photons from inhomogeneously broadened state-of-the-art solid-state emitters are estimated from the performance of the memory. Together with the immediate availability of high-quality InGaAs quantum dots emitting at 895\,nm, these results provide clear prospects for the development of a heterogeneous on-demand quantum light interface.

DOI
10.48550/arxiv.2402.14686

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Abstract Interfacing light from solid-state single-photon sources with scalable and robust room-temperature quantum memories has been a long-standing challenge in photonic quantum information technologies due to inherent noise processes and time-scale mismatches between the operating conditions of solid-state and atomic systems. Here, we demonstrate storage of single photons from a semiconductor quantum dot (QD) device in a room-temperature atomic vapor memory and their on-demand retrieval. A deterministically fabricated InGaAs QD light source emits single photons at the wavelength of the cesium D1 line at 895 nm which exhibit an inhomogeneously broadened linewidth of 5.1(7) GHz and are subsequently stored in a low-noise ladder-type cesium vapor memory. We show control over the interaction between the single photons and the atomic vapor, allowing for variable retrieval times of up to 19.8(3) ns. A maximum internal efficiency of η int = 0.6 ( 1 ) % is achieved. Our results expand the application space of both room-temperature vapor memories and semiconductor QDs in future quantum network architectures.
Quantum memories are a key technology for distributing entanglement in large-scale quantum networks. They allow for coherent control and temporal reordering of single photons which is a fundamental prerequisite for quantum repeaters, local synchronization and buffering of quantum information. These applications require bright and pure sources of indistinguishable single photons, as well as long-lived, efficient, and high-bandwidth quantum memories with minimal noise. The demonstration of robust, scalable, multi-mode photonic interfaces between different types of quantum memories and single-photon sources remains an open experimental challenge. This work contributes to this endeavor by investigating a heterogeneous interface between a semiconductor quantum dot single-photon source and a room-temperature atomic vapor memory. The first part of this work presents the first room-temperature, ladder-type atomic vapor memory that operates on the Cs D1 line at 895\,nm. The performance of the memory is characterized using attenuated laser pulses at the single-photon level. The memory achieves an internal efficiency of ηint=15(1) %\eta_\mathrm{int}=15(1)\,\%ηint​=15(1)% at a storage time of τs=17.4(2)\tau_\mathrm{s}=17.4(2)τs​=17.4(2)\,ns. We derive a quantitative benchmark for the memory compatibility with quantum dot single-photon sources. The memory's high signal-to-noise ratio of 830(80), and its spectral acceptance window of W=560\mathcal{W}=560W=560\,MHz promise compatibility with single photons from state-of-the-art InGaAs quantum dot devices. Furthermore, we present such a nano-integrated quantum dot device and characterize its optical properties. We measure a radiative lifetime of 1.3(1)\,ns and an inhomogeneously broadened linewidth of 5.1(1)\,GHz. The temperature tuning of the emission wavelength to the Cs D1 line allows coupling of the quantum dot to the memory in a joint experiment. The storage of single photons from a quantum dot source in a room-temperature atomic memory is demonstrated with on-demand retrieval. The variable storage time of up to τs=19.8\tau_\mathrm{s}=19.8τs​=19.8\,ns and the memory's fractional delay of Df=14(1)\mathrm{D}_\mathrm{f}=14(1)Df​=14(1) present a significant advancement in the research field. We compare our results with other types of interfaces between single-photon sources and quantum memories and discuss the performance in the context of quantum network applications. This work marks an important step towards local buffering and synchronization of quantum information in heterogeneous quantum network nodes.
Interfacing light from solid-state single-photon sources with scalable and robust room-temperature quantum memories has been a long-standing challenge in photonic quantum information technologies due to inherent noise processes and time-scale mismatches between the operating conditions of solid-state and atomic systems. Here, we demonstrate on-demand storage and retrieval of single photons from a semiconductor quantum dot device in a room-temperature atomic vapor memory. A deterministically fabricated InGaAs quantum dot light source emits single photons at the wavelength of the cesium D1 line at 895\,nm which exhibit an inhomogeneously broadened linewidth of 5.1(7)\,GHz and are subsequently stored in a low-noise ladder-type cesium vapor memory. We show control over the interaction between the single photons and the atomic vapor, allowing for variable retrieval times of up to 19.8(3)\,ns at an internal efficiency of ηint=0.6(1)%η_\mathrm{int}=0.6(1)\%ηint​=0.6(1)%. Our results significantly expand the application space of both room-temperature vapor memories and semiconductor quantum dots in future quantum network architectures.
Robust interfaces between single-photon sources and quantum memories are pivotal for tomorrow's quantum network architectures. The authors present a room-temperature ladder-type atomic memory for single photons at 895 nm. Comprehensive performance characterization reveals the capabilities of the memory for high bandwidth and low noise, and benchmarking shows its compatibility with state-of-the-art quantum dot single-photon sources. This work paves the way toward a heterogeneous on-demand interface between a single-photon source and an optical memory for buffering and synchronization in quantum network nodes.
Quantum memories can substantially increase the efficiency of long-distance communications by synchronizing entanglement swapping operations in quantum repeater nodes. To build a quantum memory, electromagnetically induced transparency (EIT) in atomic vapors can be exploited to coherently store light pulses even at room temperatures. As a quantum source of light, semiconductor quantum dots (QD) offer bright on-demand single photons with high purity.4 Interfacing QDs with atomic vapors has been shown by “slow light” but a quantum memory for QDs is yet to be demonstrated. In this work, we develop an EIT quantum memory hosted in warm cesium vapor. Storage of faint coherent light pulses on the single photon level shows high storage efficiency. A measured bandwidth in the order of 200 MHz makes the memory compatible with the Fourier-limited emission of QDs embedded in micropillar cavities. We show the first attempts to interface the emission from a QD-micropillar with our quantum memory by finetuning the emission wavelength of the emitters to one of the hyperfine transitions in Cs, where the EIT memory takes place. This work sets the base for a hybrid quantum memory based on atomic ensembles for an on-demand semiconductor single-photon source.