Single-photon-level optical storage in a solid-state spin-wave memory
by: N. Timoney, I. Usmani, P. Jobez, M. Afzelius, N. Gisin
UNIGE (University of Geneva) A long-lived quantum memory is a firm requirement for implementing a quantum repeater scheme. Recent progress in solid-state rare-earth-ion-doped systems justifies their status as very strong candidates for such systems. Nonetheless an optical memory based on spin-wave storage at the single-photon-level has not been shown in such a system to date, which is crucial for achieving the long storage times required for quantum repeaters. University of Geneva researchers have recently shown that it is possible to execute a complete atomic frequency comb (AFC) scheme, including spin-wave storage, with weak coherent pulses of $\barn = 2.5 \pm 0.6$ photons per pulse. We discuss in detail the experimental steps required to obtain this result and demonstrate the coherence of a stored time-bin pulse. We show a noise level of $(7.1 +/- 2.3)10-3$ photons per mode during storage, this relatively low-noise level paves the way for future quantum optics experiments using spin-waves in rare-earth-doped crystals.This is the first optical storage of a spin-wave in a solid-state memory, in the regime of a few photons per input pulse. This was made possible by a strategy of extensive filtering and by carefully shaping the temporal envelope of the strong control pulses. The final unconditional noise floor of (7.1 +/- 2.3) 10-3 is low enough to allow for quantum schemes using spin-wave storage and manipulation, such as the generation of quantum-correlated spin-wave and photonic excitations using variant of the DLCZ approach adapted to the solid-state. These schemes will, in turn, allow for generation of entanglement between light and matter and entanglement of solid-state remote quantum memories, a basic building block for quantum repeaters.
Workpackage: wp-2.3: Quantum memories and interfaces
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