Towards a compact and transportable solid-state quantum memory

Abstract

The distribution of entanglement over long-distance quantum networks requires quantum repeaters placed along the network, since otherwise it is impeded by losses in the quantum channels. A possible implementation of quantum repeaters is based on quantum memories paired with sources of entangled photons. In this thesis, we present the design, construction, and characterization of compact solid-state quantum memory hardware based on a Pr3+:Y2SiO5 crystal. The hardware encompasses an AOM rack for precise optical pulse shaping, a laser system stabilized via the Pound-Drever-Hall (PDH) technique, and a cryogenically cooled Pr3+:Y2SiO5 sample on an optical table setup with small footprint. We measure the efficiency, temporal response, and thermal stability of the AOM rack, and we estimate a stabilized laser linewidth of 2.7(3) kHz. Additionally, we characterize the quantum memory crystal within our setup, measuring an inhomogeneous broadening of 11.2(4) GHz and a coherence time (T2) of 58(11) μs, which corresponds to an homogeneous linewidth of 5.5(10) kHz. This confirms the suitability of the hardware for the implementation of the AFC protocol as a quantum memory protocol. The advancements present in this compact system constitute a key step towards the deployment of rackintegrated quantum repeater nodes for long-distance quantum communication networks.