Quantum Storage of Qubits in an Array of Independently Controllable Solid-State Quantum Memories

Abstract

Random-access quantum memories may offer computational advantages for quantum computers and networks. In this paper, we advance arrays of solid-state quantum memories towards their usage as random-access quantum memory. We perform quantum storage of path and time-bin qubits implemented with weak coherent states at the single-photon level, in an array of ten temporally-multiplexed memory cells with controllable addressing. The qubits can be stored in arbitrary combinations of memory cells, from which they are read-out on demand. We find average fidelities of $95_{-2}^{+2}\;\%$ for path qubits and $91^{+2}_{-2}\;\%$ for time-bin qubits. The measured fidelities violate the classical bounds for both encodings and for all ten cells. We also sequentially store a time-bin qubit in two different memory cells, maintain both qubits simultaneously in the array, and perform a collective read-out. The individual control paired with high storage fidelity represents a significant advance towards a solid-state random-access quantum memory for quantum repeaters and photonic quantum processors.