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)% at a storage time of
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\,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\,ns and the memory's fractional delay of
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.
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
ηint=15(1)% and an estimated
1/e-storage time of
τs≈32ns. 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.
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)%. Our results significantly expand the application space of both room-temperature vapor memories and semiconductor quantum dots in future quantum network architectures.
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.
Future quantum photonic networks require coherent optical memories, preferably operating at room temperature, for synchronizing quantum sources and gates of probabilistic nature. Until now, however, room-temperature atomic memories have suffered from an intrinsic read-out noise. Here we demonstrate a fast ladder memory (FLAME) mapping the optical field onto the superposition between electronic orbitals of rubidium vapor. Employing a ladder level-system of orbital transitions with nearly degenerate frequencies simultaneously enables high bandwidth, low noise, and long memory lifetime. We store and retrieve 1.7-ns-long pulses, containing 0.5 photons on average, and observe short-time external efficiency of 25%, memory lifetime (1/e) of 86 ns, and below 10−4 added noise photons. Consequently, coupling this memory to a probabilistic source would enhance the on-demand photon generation probability by a factor of 12, the highest number yet reported for a noise-free, room-temperature memory. This paves the way towards the controlled production of large quantum states of light from probabilistic photon sources.