Single Spin Optically Detected Magnetic Resonance with E-Band Microwave Resonators

TL;DR

This paper develops microwave resonators for single electron spin resonance at high frequencies up to 90 GHz, enabling optical readout and coherent control of spins in high magnetic fields, extending quantum sensing capabilities.

Contribution

It introduces MW resonators compatible with optical single spin readout at high frequencies and magnetic fields up to 3 T, expanding the operational range for single spin quantum technologies.

Findings

Resonators achieve MW efficiency of 1.36 mT/√W.

Optical spin readout properties are retained up to 3 T.

Coherent control of single nuclear spins demonstrated at high fields.

Abstract

Magnetic resonance with ensembles of electron spins is nowadays performed in frequency ranges up to 240 GHz and in corresponding magnetic fields of up to 10 T. However, experiments with single electron and nuclear spins so far only reach into frequency ranges of several 10 GHz, where existing coplanar waveguide structures for microwave (MW) delivery are compatible with single spin readout techniques (e.g. electrical or optical readout). Here, we explore the frequency range up to 90 GHz, respectively magnetic fields of up to $\approx 3\,$T for single spin magnetic resonance in conjunction with optical spin readout. To this end, we develop MW resonators with optical single spin access. In our case, rectangular E-band waveguides guarantee low-loss supply of microwaves to the resonators. Three dimensional cavities, as well as coplanar waveguide resonators enhance MW fields by spatial and spectral confinement with a MW efficiency of $1.36\,\mathrm{mT/\sqrt{W}}$. We utilize single NV centers as hosts for optically accessible spins, and show, that their properties regarding optical spin readout known from smaller fields (<0.65 T) are retained up to fields of 3 T. In addition, we demonstrate coherent control of single nuclear spins under these conditions. Furthermore, our results extend the applicable magnetic field range of a single spin magnetic field sensor. Regarding spin based quantum registers, high fields lead to a purer product basis of electron and nuclear spins, which promises improved spin lifetimes. For example, during continuous single-shot readout the $^{14}$N nuclear spin shows second-long longitudinal relaxation times.