School of Electrical Engineering and Telecommunications, UNSW Sydney, Sydney, NSW 2052, Australia.
Accelerator Technology and Applied Physics Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
Sci Adv. 2023 Mar 10;9(10):eadg1593. doi: 10.1126/sciadv.adg1593.
The use of superconducting microresonators together with quantum-limited Josephson parametric amplifiers has enhanced the sensitivity of pulsed electron spin resonance (ESR) measurements by more than four orders of magnitude. So far, the microwave resonators and amplifiers have been designed as separate components due to the incompatibility of Josephson junction-based devices with magnetic fields. This has produced complex spectrometers and raised technical barriers toward adoption of the technique. Here, we circumvent this issue by coupling an ensemble of spins directly to a weakly nonlinear and magnetic field-resilient superconducting microwave resonator. We perform pulsed ESR measurements with a 1-pL mode volume containing 6 × 10 spins and amplify the resulting signals within the device. When considering only those spins that contribute to the detected signals, we find a sensitivity of [Formula: see text] for a Hahn echo sequence at a temperature of 400 mK. In situ amplification is demonstrated at fields up to 254 mT, highlighting the technique's potential for application under conventional ESR operating conditions.
超导微谐振器与量子限制约瑟夫森参量放大器的结合，将脉冲电子自旋共振（ESR）测量的灵敏度提高了四个数量级以上。到目前为止，由于基于约瑟夫森结的器件与磁场不兼容，微波谐振器和放大器被设计为单独的组件。这导致了复杂的光谱仪，并对该技术的采用构成了技术障碍。在这里，我们通过将一组自旋直接耦合到一个弱非线性和磁场弹性的超导微波谐振器来规避这个问题。我们在一个包含 6×10 个自旋的 1-pL 模式体积中进行了脉冲 ESR 测量，并在器件内放大了产生的信号。当仅考虑那些对检测信号有贡献的自旋时，我们在 400 mK 的温度下发现[公式：见文本]的哈恩回波序列的灵敏度。在高达 254 mT 的场下实现了原位放大，突出了该技术在传统 ESR 操作条件下应用的潜力。
