Microwave multimode memory with an Er$^{3+}$:Y$_2$SiO$_5$ spin ensemble

TL;DR

This paper demonstrates multimode microwave photon storage and retrieval using an Er$^{3+}$:Y$_2$SiO$_5$ spin ensemble at milli-Kelvin temperatures, highlighting its potential for hybrid quantum computing and communication.

Contribution

It presents the first demonstration of multimode microwave memory with an Er$^{3+}$:Y$_2$SiO$_5$ ensemble, including detailed ESR characterization and coherence properties.

Findings

Stored and retrieved up to 16 microwave pulses

Memory efficiency of 10$^{-4}$ at T₂=5.6 μs

Identified coherence time and multimode capacity

Abstract

Interfacing photonic and solid-state qubits within a hybrid quantum architecture offers a promising route towards large scale distributed quantum computing. In that respect, hybrid quantum systems combining circuit QED with ions doped into solids are an attractive platform. There, the ions serve as coherent memory elements and reversible conversion elements of microwave to optical qubits. Among many possible spin-doped solids, erbium ions offer the unique opportunity of a coherent conversion of microwave photons into the telecom C-band at $1.54\,\mu$m employed for long distance communication. In our work, we perform a time-resolved electron spin resonance study of an Er$^{3+}$:Y$_2$SiO$_5$ spin ensemble at milli-Kelvin temperatures and demonstrate multimode storage and retrieval of up to 16 coherent microwave pulses. The memory efficiency is measured to be 10$^{-4}$ at the coherence time of $T_2=5.6\,\mu$s.