Narrow optical linewidths in erbium implanted in TiO$_2$

TL;DR

This study demonstrates that erbium ions implanted into TiO$_2$ exhibit narrow optical and spin linewidths, showing promise for quantum applications due to the host's low nuclear spin noise and successful implantation.

Contribution

It introduces a new method of incorporating erbium ions into TiO$_2$ via ion implantation, achieving narrow linewidths comparable to traditional hosts.

Findings

40% incorporation yield of Er$^{3+}$ into TiO$_2$

Optical linewidth of 460 MHz

Spin linewidth of 20 MHz

Abstract

Atomic and atom-like defects in the solid-state are widely explored for quantum computers, networks and sensors. Rare earth ions are an attractive class of atomic defects that feature narrow spin and optical transitions that are isolated from the host crystal, allowing incorporation into a wide range of materials. However, the realization of long electronic spin coherence times is hampered by magnetic noise from abundant nuclear spins in the most widely studied host crystals. Here, we demonstrate that Er$^{3+}$ ions can be introduced via ion implantation into TiO$_2$, a host crystal that has not been studied extensively for rare earth ions and has a low natural abundance of nuclear spins. We observe efficient incorporation of the implanted Er$^{3+}$ into the Ti$^{4+}$ site (40% yield), and measure narrow inhomogeneous spin and optical linewidths (20 and 460 MHz, respectively) that are comparable to bulk-doped crystalline hosts for Er$^{3+}$. This work demonstrates that ion implantation is a viable path to studying rare earth ions in new hosts, and is a significant step towards realizing individually addressed rare earth ions with long spin coherence times for quantum technologies.