Gigahertz-Bandwidth Optical Memory in Pr$^{3+}$:Y$_2$SiO$_5$

TL;DR

This paper demonstrates a broadband optical memory in Pr$^{3+}$:Y$_2$SiO$_5$ capable of storing 5 GHz bandwidth pulses with up to 10% efficiency, enabling multiple temporal modes, advancing quantum memory technology.

Contribution

The study introduces a novel broadband AFC protocol matching inhomogeneous broadening, achieving high bandwidth storage exceeding hyperfine splitting in Pr$^{3+}$:Y$_2$SiO$_5$.

Findings

Maximum efficiency of 10% at 12.5 ns rephasing time

Storage of up to 12 temporal modes

Bandwidth matching inhomogeneous broadening (~5 GHz)

Abstract

We experimentally study a broadband implementation of the atomic frequency comb (AFC) rephasing protocol with a cryogenically cooled Pr$^{3+}$:Y$_2$SiO$_5$ crystal. To allow for storage of broadband pulses, we explore a novel regime where the input photonic bandwidth closely matches the inhomogeneous broadening of the material $(\sim5\,\textrm{GHz})$, thereby significantly exceeding the hyperfine ground and excited state splitting $(\sim10\,\textrm{MHz})$. Through an investigation of different AFC preparation parameters, we measure a maximum efficiency of $10\%$ after a rephasing time of $12.5\,$ns. With a suboptimal AFC, we witness up to 12 rephased temporal modes.