Inductive detection and amplification of spin echoes using a superconducting parametric amplifier

In recent years, the cQED toolkit has been successfully applied to push the boundary of measurement sensitivity in electron spin resonance (ESR) spectroscopy [1,2,3]. In particular, the adoption of Josephson Parametric Amplifiers has allowed the noise in ESR spectrometers to approach the quantum limit. Here we report the use of a degenerate parametric amplifier (DPA) to perform in-situ amplification of spin echo signals in pulsed ESR measurements of ²⁰⁹Bi donors in Silicon. Unlike previous work, the spins here have a direct inductive coupling to the DPA, which is constructed from a quarter-wavelength resonator in a thin NbTiN film. The DPA serves as both the ESR cavity and first-stage amplifier for spin echo signals. We show that the device is capable of operating in a magnetic field of 250 mT and greatly enhances the SNR of pulsed ESR measurements.

[1] A. Bienfait, et. al. Reaching the quantum limit of sensitivity in electron spin resonance. Nature Nano. 11(3):253 (2016)
[2] C. Eichler, et. al. Electron spin resonance at the level of 10⁴ spins using low impedance superconducting resonators. Phys. Rev. Lett. 118(3): 037701 (2017)
[3] V. Ranjan, et. al. Electron spin resonance spectroscopy with femtoliter detection volume. Appl. Phys. Lett. 116:184002 (2020)