In-situ amplification of spin echoes within a kinetic inductance parametric amplifier

TL;DR

This paper introduces an in-situ spin echo amplification technique using a magnetic field-resilient superconducting resonator, enabling sensitive ESR measurements at higher magnetic fields without complex setups.

Contribution

It presents a novel method to directly couple spins to a superconducting resonator, allowing in-situ amplification and operation under moderate magnetic fields, simplifying ESR measurement setups.

Findings

Achieved single-shot Hahn echo sensitivity of 2.8×10^3 spins.

Demonstrated operation at magnetic fields up to 254 mT.

Used a magnetic field-resilient superconducting film for resonator construction.

Abstract

The use of superconducting micro-resonators in combination with quantum-limited Josephson parametric amplifiers has in recent years lead to more than four orders of magnitude improvement in the sensitivity of pulsed Electron Spin Resonance (ESR) measurements. So far, the microwave resonators and amplifiers have been designed as separate components, largely due to the incompatibility of Josephson junction-based devices with even moderate magnetic fields. This has led to complex spectrometers that operate under strict environments, creating technical barriers for the widespread adoption of the technique. Here we circumvent this issue by inductively coupling an ensemble of spins directly to a weakly nonlinear microwave resonator, which is engineered from a magnetic field-resilient thin superconducting film. We perform pulsed ESR measurements with a $1$~pL effective mode volume and amplify the resulting spin signal using the same device, ultimately achieving a sensitivity of $2.8 \times 10^3$ spins in a single-shot Hahn echo measurement at a temperature of 400 mK. We demonstrate the combined functionalities at fields as large as 254~mT, highlighting the technique's potential for application under more conventional ESR operating conditions.