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.
For many quantum-photonic applications highly efficient and fast single-photon detectors are of utmost importance. Resonant tunneling diode (RTD) photodetectors can be operated as low-noise and high-speed amplifiers of small optically generated electrical signals. For this purpose, RTD photodetectors exploit that the tunneling current is extremely sensitive to changes in the local electrostatic potential, which enables the detection of single photogenerated minority charge carriers, and hence the detection of single photons with the capability of photon-number resolution. Here, we present different RTD device geometries and operation schemes for enhanced quantum-efficiency and operation frequencies.
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