A solid state spin-wave quantum memory for time-bin qubits

TL;DR

This paper reports the first solid-state spin-wave quantum memory capable of storing and on-demand reading of time-bin qubits with high fidelity, advancing scalable quantum network technology.

Contribution

It introduces a novel solid-state quantum memory for time-bin qubits using atomic frequency combs in ext{PrYSO} crystals with on-demand read-out and noise filtering.

Findings

Successful storage of weak coherent pulses at the single-photon level.

Conditional fidelities exceeding classical limits for time-bin qubits.

Achieved low unconditional noise level of approximately 0.002 photons per pulse.

Abstract

We demonstrate the first solid-state spin-wave optical quantum memory with on-demand read-out. Using the full atomic frequency comb scheme in a \PrYSO crystal, we store weak coherent pulses at the single-photon level with a signal to noise ratio $> 10$. Narrow-band spectral filtering based on spectral hole burning in a second \PrYSO crystal is used to filter out the excess noise created by control pulses to reach an unconditional noise level of $(2.0 \pm 0.3) \times10^{-3}$ photons per pulse. We also report spin-wave storage of photonic time-bin qubits with conditional fidelities higher than a measure and prepare strategy, demonstrating that the spin-wave memory operates in the quantum regime. This makes our device the first demonstration of a quantum memory for time-bin qubits, with on demand read-out of the stored quantum information. These results represent an important step for the use of solid-state quantum memories in scalable quantum networks.