Optical coherence of Er$^{3+}$:Y$_2$O$_3$ ceramics for telecommunication quantum technologies

TL;DR

This study demonstrates that Er$^{3+}$:Y$_2$O$_3$ ceramics exhibit exceptionally narrow optical linewidths and long spectral hole lifetimes at millikelvin temperatures, making them promising for quantum communication technologies.

Contribution

The paper reports the narrowest optical homogeneous linewidth in rare-earth doped ceramics and characterizes the dephasing mechanisms, advancing the potential of Er$^{3+}$:Y$_2$O$_3$ for quantum memory applications.

Findings

Optical homogeneous linewidth of 580 Hz at millikelvin temperatures.

Spectral hole lifetimes up to 5 seconds.

Dephasing mainly due to elastic two-level systems and hyperfine interactions.

Abstract

We report an optical homogeneous linewidth of 580 $\pm$ 20 Hz of Er$^{3+}$:Y$_2$O$_3$ ceramics at millikelvin temperatures, narrowest so far in rare-earth doped ceramics. We show slow spectral diffusion of $\sim$2 kHz over a millisecond time scale. Temperature, field dependence of optical coherence and spectral diffusions reveal the remaining dephasing mechanism as elastic two-level systems in polycrystalline grain boundaries and superhyperfine interactions of Er$^{3+}$ with nuclear spins. In addition, we perform spectral holeburning and measure up to 5 s hole lifetimes. These spectroscopic results put Er$^{3+}$:Y$_2$O$_3$ ceramics as a promising candidate for telecommunication quantum memories and light-matter interfaces.