Storage and retrieval of microwave fields at the single-photon level in a spin ensemble

TL;DR

This paper demonstrates the storage and retrieval of microwave single-photon level signals in a diamond spin ensemble coupled to a superconducting resonator, showing potential for quantum memory applications.

Contribution

It presents the first experimental demonstration of microwave photon storage at the single-photon level in a large spin ensemble with quantifiable efficiency.

Findings

Storage efficiency of 0.3% of absorbed energy

Signal retrieval after 100 microseconds

Agreement between experimental results and simulations

Abstract

We report the storage of microwave pulses at the single-photon level in a spin-ensemble memory consisting of $10^{10}$ NV centers in a diamond crystal coupled to a superconducting LC resonator. The energy of the signal, retrieved $100\, \mu \mathrm{s}$ later by spin-echo techniques, reaches $0.3\%$ of the energy absorbed by the spins, and this storage efficiency is quantitatively accounted for by simulations. This figure of merit is sufficient to envision first implementations of a quantum memory for superconducting qubits.