Coherent spin control at the quantum level in an ensemble-based optical memory

TL;DR

This paper demonstrates spin-echo control of a single spin excitation in a solid-state ensemble, enabling millisecond-scale quantum memory storage with high readout fidelity, advancing long-term optical quantum storage.

Contribution

It shows the first successful spin-echo manipulation of a mean spin excitation in a solid-state ensemble, overcoming previous dephasing limitations for quantum memories.

Findings

Achieved millisecond-scale storage of spin excitations.

Demonstrated high signal-to-noise optical readout after storage.

Validated spin-echo techniques for ensemble-based quantum memories.

Abstract

Long-lived quantum memories are essential components of a long-standing goal of remote distribution of entanglement in quantum networks. These can be realized by storing the quantum states of light as single-spin excitations in atomic ensembles. However, spin states are often subjected to different dephasing processes that limit the storage time, which in principle could be overcome using spin-echo techniques. Theoretical studies have suggested this to be challenging due to unavoidable spontaneous emission noise in ensemble-based quantum memories. Here we demonstrate spin-echo manipulation of a mean spin excitation of 1 in a large solid-state ensemble, generated through storage of a weak optical pulse. After a storage time of about 1 ms we optically read out the spin excitation with a high signal-to-noise ratio. Our results pave the way for long-duration optical quantum storage using spin-echo techniques for any ensemble-based memory.