The coherent storage, buffering and retrieval of photons in a quantum memory enables the scalable creation of photonic entangled states via linear optics and repeat-until success, unlocking applications in quantum communications and photonic quantum computing. Quantum memories based on off-resonant cascaded absorption (ORCA) in atomic vapors allow this storage to be broadband, noise free, and high efficiency. Here, we implement a cavity-enhanced ORCA memory with reduced footprint and reduced power requirements compared to conventional single-pass schemes. By combining a strong magnetic field with polarization control, we maintain a Doppler-free interaction and eliminate the need for optical pumping. Our design establishes the feasibility of large arrays of ultracompact, low-power, near-unit efficiency, noiseless quantum memories running at GHz bandwidth, without the need for atom trapping or cryogenics.
The coherent storage, buffering and retrieval of photons in a quantum memory enables the scalable creation of photonic entangled states via linear optics and repeat-until success, unlocking applications in quantum communications and photonic quantum computing. Quantum memories based on off-resonant cascaded absorption (ORCA) in atomic vapors allow this storage to be broadband, noise free, and high efficiency. Here, we implement a cavity-enhanced ORCA memory with reduced footprint and reduced power requirements compared to conventional single-pass schemes. By combining a strong magnetic field with polarization control, we maintain a Doppler-free interaction and eliminate the need for optical pumping. Our design establishes the feasibility of large arrays of ultracompact, low-power, near-unit efficiency, noiseless quantum memories running at GHz bandwidth, without the need for atom trapping or cryogenics.
Optical quantum memories are devices that store and recall quantum light and are vital to the realization of future photonic quantum networks. To date, much effort has been put into improving storage times and efficiencies of such devices to enable long-distance communications. However, less attention has been devoted to building quantum memories which add zero noise to the output. Even small additional noise can render the memory classical by destroying the fragile quantum signatures of the stored light. Therefore, noise performance is a critical parameter for all quantum memories. Here we introduce an intrinsically noise-free quantum memory protocol based on two-photon off-resonant cascaded absorption (ORCA). We demonstrate successful storage of GHz-bandwidth heralded single photons in a warm atomic vapor with no added noise, confirmed by the unaltered photon-number statistics upon recall. Our ORCA memory meets the stringent noise requirements for quantum memories while combining high-speed and room-temperature operation with technical simplicity, and therefore is immediately applicable to low-latency quantum networks.
Light is an ideal information carrier for quantum networks: its quantum properties are not degraded by noise in ambient conditions and it has a large information capacity owing to its high bandwidth. However, quantum technologies based on photonic networks have been hampered by the exponentially poor scaling of the underlying probabilistic quantum operations. Quantum optical memories, devices that store, manipulate, and release on- demand quantum light, have been identified as an indispensable network component, because they facilitate scalability. Noise-free operation of the memory is critical, since even small additional noise can render the memory classical by destroying the quantum character of the light. Here I introduce a new broadband quantum memory protocol - the off-resonant cas- caded absorption (ORCA) memory - that is inherently noise-free and operates in ambient conditions. I model ORCA theoretically, after which I characterise the classical perfor- mance of a proof-of-concept implementation in warm caesium vapour, using weak near- infrared coherent states. In order to verify quantum operation of the ORCA memory, I interface it with a broadband heralded single-photon source. I measure and compare the quantum statistics of the stored and retrieved light, observing for the first time their full preservation in a room-temperature atomic quantum memory. Finally, I make headway into integrating the ORCA vapour memory by investigating an alkali-filled hollow-core fibre platform. I use light-induced atomic desorption (LIAD) to demonstrate record- breaking alkali vapour densities in fibre, a prerequisite for efficient memory operation. Because of its technical simplicity and integrability, its high bandwidth and its low noise, ORCA provides a viable route towards next generation, photonic quantum network technologies.
Future optical quantum technologies, such as quantum networks, distributed quantum computing and sensing, demand efficient, broadband quantum memories. However, achieving high efficiency without introducing noise, reducing bandwidth, or limiting scalability remains a challenge. Here, we present an approach to enhance quantum memory protocols by leveraging constructive light–matter interference, leading to an increase in memory efficiency without increasing atomic density or laser intensity. We implement this method in a Raman quantum memory in warm cesium vapor and achieve more than a threefold improvement in total efficiency, reaching (34.3±8.4)%, while retaining GHz-bandwidth operation and low noise levels. Numerical simulations predict that this approach can boost efficiencies in systems limited by atomic density, such as cold atomic ensembles, from 65% to beyond 96%, while in warm atomic vapors, it could reduce the laser intensity needed to reach a given efficiency by over an order-of-magnitude, exceeding 95% total efficiency. Furthermore, our method preserves the single-mode nature of the memory at high efficiencies. This protocol is applicable to various memory architectures, paving the way toward scalable, efficient, low-noise, and high-bandwidth quantum memories.
Future optical quantum technologies, such as quantum networks, distributed quantum computing and sensing, demand efficient, broadband quantum memories. However, achieving high efficiency without introducing noise, reducing bandwidth, or limiting scalability remains a challenge. Here, we present a new approach to enhance quantum memory protocols by leveraging constructive light-matter interference, leading to an increase in memory efficiency without increasing atomic density or laser intensity. We implement this method in a Raman quantum memory in warm Cesium vapor, and achieve more than a three-fold improvement in total efficiency reaching (34.3±8.4)%, while retaining GHz-bandwidth operation and low noise levels. Numerical simulations predict that this approach can boost efficiencies in systems limited by atomic density, such as cold atomic ensembles, from 65% to beyond 96%, while in warm atomic vapors it could reduce the laser intensity needed to reach a given efficiency by over an order-of-magnitude, exceeding 95% total efficiency. Furthermore, our method preserves the single-mode nature of the memory at high efficiencies. This new protocol is applicable to various memory architectures, paving the way toward scalable, efficient, low-noise, and high-bandwidth quantum memories.
We present a demonstration of simultaneous high-efficiency, high-speed, and low-noise operation of a photonic quantum memory. By leveraging controllable collisional dephasing in a neutral barium atomic vapor, we demonstrate a significant improvement in memory efficiency and bandwidth over existing techniques. We achieve greater than 95% storage efficiency and 26% total efficiency of 880 GHz bandwidth photons, with O(10−5) noise photons per retrieved pulse. These ultrabroad bandwidths enable rapid quantum information processing and contribute to the development of practical quantum memories with potential applications in quantum communication, computation, and networking.
The Off-Resonant Cascaded Absorption (ORCA) protocol in warm atomic vapors offers a scalable platform for high-bandwidth, low noise quantum memories, but its coherence time is fundamentally limited by Doppler-induced dephasing. We introduce and experimentally demonstrate a dynamic rephasing protocol that counteracts Doppler dephasing in a telecom-band ORCA quantum memory. By transferring the stored excitation to an auxiliary shelving state, we effectively reverse the accumulated Doppler phase and extend the storage time by a factor of 50 while preserving the memory's GHz bandwidth and low noise. Using this protocol, we then demonstrate on-demand storage and retrieval of four independent time-bin modes within a single warm vapor memory -- showing that Doppler dephasing can alternatively be harnessed for high-dimensional temporal mode processing. Our results establish rephasing in warm atomic vapors as a viable route toward high-bandwidth, temporally multiplexed quantum memories operating at room temperature.