Extending the spin coherence lifetimes of ${}^{167}$Er$^{3+}$$:$Y$_2$SiO$_5$ at subkelvin temperatures

TL;DR

This study significantly extends the electron and nuclear spin coherence times in Er$^{3+}$:Y$_2$SiO$_5$ at subkelvin temperatures, enhancing its potential for quantum memory and transducer applications.

Contribution

It demonstrates a 40-fold increase in electron spin coherence time and a substantial rise in nuclear spin coherence time at subkelvin temperatures using pulsed-electron-nuclear-double-resonance.

Findings

Electron spin coherence time reached 290 μs, a 40-fold increase.

Nuclear spin coherence time extended to 738 μs.

Rapid increase in coherence times observed at subkelvin temperatures.

Abstract

Er$^{3+}$$:$Y$_2$SiO$_5$ is a material of particular interest due to its suitability for telecom-band quantum memories and quantum transducers interfacing optical communication with quantum computers working in the microwave regime. Extending the coherence lifetimes of the electron spins and the nuclear spins is essential for implementing efficient quantum information processing based on such hybrid electron-nuclear spin systems. The electron spin coherence time of Er$^{3+}$$:$Y$_2$SiO$_5$ is so far limited to several microseconds, and there are significant challenges in optimizing coherence lifetimes simultaneously for both the electron and nuclear spins. Here we perform a pulsed-electron-nuclear-double-resonance investigation for an Er$^{3+}$-doped material at subkelvin temperatures. At the lowest working temperature, the electron spin coherence time reaches 290 $\pm$ 17 $\mu$s, which has been enhanced by 40 times compared with the previous results. In the subkelvin regime, a rapid increase in the nuclear spin coherence time is observed, and the longest coherence time of 738 $\pm$ 6 $\mu$s is obtained. These extended coherence lifetimes could be valuable resources for further applications of Er$^{3+}$$:$Y$_2$SiO$_5$ in fiber-based quantum networks.