Quantum memories play a pivotal role in establishing long-distance communication by entanglement swapping operations within quantum repeater nodes. Constructing such a quantum memory involves Electromagnetically Induced Transparency (EIT) within atomic vapors at room temperatures to store highly attenuated coherent light pulses down to the level of single photons. The photons may be generated from quantum nodes containing stationary quantum systems, such as atoms or semiconductor quantum dots (QDs). QDs serve as a potent source of quantum light, furnishing bright, precisely timed single photons of exceptional purity. While previous endeavors have demonstrated the integration of QDs with atomic vapors through techniques like “slow light,” the development of a dedicated quantum memory for QDs remains unmatched. In our study, we introduce an EIT quantum memory hosted within warm cesium vapor. Our approach exhibits a good efficiency in storing faint coherent light pulses at the single photon level. Moreover, the measured bandwidth of around 200 MHz approaches the Fourier-limited emission characteristics of QDs. We present initial efforts to match the emission from QDs with our quantum memory and discuss application scenarios of room temperature EIT quantum memories.
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.
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