Telecom-heralded entanglement between multimode solid-state quantum memories

Topical White Paper: A Case for Quantum Memories in Space

“…This feature, in conjunction with the absence of thermal motion, render REIDs as a high-performance QM platform. The recent achievements include but are not limited to; heralded entanglement generation between two QMs [69,70] in a quantum repeater setting, bright pulse storage from minute [71] to hourlong time scales [10] and demonstration of temporal [72][73][74] spectral [75,76] and spatial [77] multimode storage. The other research direction is the miniaturization of these devices: waveguide structures [78][79][80] and nanophotonic cavities [81,82] offer an enhanced compactness and interaction strength.…”

“…More effectively, the SPDC source can be placed inside a resonant cavity to reduce the linewidth while maintaining a high level of photon counts, which can yield very narrow, tunable bandwidth. For example, a highly degenerate photon-pair source that emits one photon resonant with a Prdoped REID QM and the other at the telecommunications C-band [91] was successfully used for entangling two crystals [69], and a sub-MHz linewidth source that operates at the Rb D1 line [92] was demonstrated. Even though there is great progress towards creating such narrow band sources, the strict bandwidth requirements can further be relaxed for coupling to larger bandwidth QMs.…”

“…We should note that the different quantum memory platforms we summarized above are all in different stages of development and they offer different performances for different applications. For example, the current status of single photon level experiments with REIDs are relatively advanced [69,115,116] but these systems require cryogenics and even high B-fields for specific experiments (> 1 T) [10,117]. On the other hand, such experiments are not nearly as advanced in warm vapour systems; nevertheless they do not need cryogenics or additional trapping lasers such as those needed in ultracold atoms, thus opening a path towards miniaturization and robust integration into satellite platforms.…”

Sample-efficient adaptive calibration of quantum networks using Bayesian optimization

“…Yet, there has been little effort on algorithmic optimization of quantum communications and networks [15][16][17][18]. In particular, to use such methods to overcome unavoidable channel-induced variations of properties (degrees of freedom) of photons, along with the well-known impacts of loss and noise, which restrict demonstrations of advanced, multi-qubit, quantum networks, especially those which crucially rely on interference [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33]. These variations, which originate from changes in the environment, render photons distinguishable, thereby restricting their ability to interfere [34].…”

Linear and continuous variable spin-wave processing using a cavity-coupled atomic ensemble

“…Recent experiments have introduced a path to use collective spin-wave excitations, holographically multiplexed, to achieve high-capacity quantum memories [6][7][8][9][10], but these experiments have not introduced a method to achieve full linear controllability of spin-wave excitations, a prerequisite for a universal quantum processor. Spin-wave quantum systems are being realized in multiple physical platforms including atomic vapors [7][8][9][10], solid-state crystals [11][12][13], and superconducting circuits [14]. Proposals for spin-wave readout of atomic arrays have also been developed [15][16][17].…”