The faithful storage and coherent manipulation of quantum states with matter-systems would enable the realization of large-scale quantum networks based on quantum repeaters. To achieve useful communication rates, highly multimode quantum memories are required to construct a multiplexed quantum repeater. Here, we present a demonstration of on-demand storage of orbital-angular-momentum states with weak coherent pulses at the single-photon-level in a rare-earth-ion-doped crystal. Through the combination of this spatial degree-of-freedom (DOF) with temporal and spectral degrees of freedom, we create a multiple-DOF memory with high multimode capacity. This device can serve as a quantum mode converter with high fidelity, which is a fundamental requirement for the construction of a multiplexed quantum repeater. This device further enables essentially arbitrary spectral and temporal manipulations of spatial-qutrit-encoded photonic pulses in real time. Therefore, the developed quantum memory can serve as a building block for scalable photonic quantum information processing architectures.

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151 Eu 3+ -doped yttrium silicate ( 151 Eu 3+ : Y 2 SiO 5 ) crystal is a unique material that possesses hyperfine states with coherence time up to 6 h. Many efforts have been devoted to the development of this material as optical quantum memories based on the bulk crystals, but integrable structures (such as optical waveguides) that can promote 151 Eu 3+ : Y 2 SiO 5 -based quantum memories to practical applications, have not been demonstrated so far. Here we report the fabrication of type II waveguides in a 151 Eu 3+ : Y 2 SiO 5 crystal using femtosecond-laser micromachining. The resulting waveguides are compatible with single-mode fibers and have the smallest insertion loss of 4.95 dB. On-demand light storage is demonstrated in a waveguide by employing the spinwave atomic frequency comb (AFC) scheme and the revival of silenced echo (ROSE) scheme. We implement a series of interference experiments based on these two schemes to characterize the storage fidelity. Interference visibility of the readout pulse is 0.99 ± 0.03 for the spin-wave AFC scheme and 0.97 ± 0.02 for the ROSE scheme, demonstrating the reliability of the integrated optical memory.

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Stretchable and piezoelectrically self-chargeable supercapacitor designed by sandwiching piezo-electrolyte shows high efficiency of energy collection, conversion, and self-charging, either under continuous slight palm patting or repeated stretching.

In this paper, a systematic design and analysis of thin film crystalline silicon solar cells incorporated with a new style of multilayer silver (Ag) nanoparticles (NPs) array is presented. Using numerical simulations, we showed that multilayer Ag NPs provide better light trapping than single layer Ag NPs when the Ag NPs are located on the rear of the solar cell. Furthermore, Ag NP double layers on the rear achieved the best light absorption enhancement for solar cells. Ag NP double layers showed a 6.65% increase in intergraded quantum efficiency across the solar spectrum compared with single layer structures. The parasitic absorption occurring in Ag NP bottom layers was also discussed.