| Description |
In a conventional electron spin resonance (ESR) spectrometer based on the inductive detection method, the paramagnetic spins precess in an external magnetic field radiating weak microwave signals into a resonant cavity. Despite its widespread use, ESR spectroscopy has limited sensitivity and large amounts of spins ~10^12 are necessary to accumulate sufficient signal. Exploiting recent progress in circuit-quantum electrodynamics, we have combined high quality factor superconducting micro-resonators and noise-less Josephson Parametric Amplifiers to perform ESR spectroscopy at millikelvin temperatures, reaching a new regime where the sensitivity is limited by the quantum vacuum fluctuations of the microwave field. In this talk, I will discuss this new ESR regime and its prospects for quantum technologies.
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