Proposal for detection of a single electron spin in a microwave resonator

TL;DR

This paper proposes a method to detect a single electron spin in a crystal using a high-Q superconducting resonator with nanometric constrictions, enabling rapid and high-fidelity detection.

Contribution

It introduces a novel detection scheme combining nanometric resonator constrictions and advanced signal analysis to improve single-spin detection sensitivity and speed.

Findings

Coupling constant of 5-10 kHz achieved

Single spin detection within a few milliseconds

Bayesian analysis improves detection sensitivity by ~30%

Abstract

We propose a method for detecting the presence of a single spin in a crystal by coupling it to a high-quality factor superconducting planar resonator. By confining the microwave field in a constriction of nanometric dimensions, the coupling constant can be as high as $5-10$\,kHz. This coupling affects the amplitude of the field emitted by the resonator, and the integrated homodyne signal allows detection of a single spin with unit signal-to-noise ratio within few milliseconds. We further show that a stochastic master equation approach and a Bayesian analysis of the full time dependent homodyne signal improves this figure by $\sim 30\%$ for typical parameters.