Latched detection of zeptojoule spin echoes with a kinetic inductance parametric oscillator.

Vine, Wyatt; Kringhøj, Anders; Savytskyi, Mykhailo; Parker, Daniel; Schenkel, Thomas; Johnson, Brett C; McCallum, Jeffrey C; Morello, Andrea et al. · Sci Adv · 2024

basic_science · Level V

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Abstract

When strongly pumped at twice their resonant frequency, nonlinear resonators develop a high-amplitude intracavity field, a phenomenon known as parametric self-oscillations. The boundary over which this instability occurs can be extremely sharp and thereby presents an opportunity for realizing a detector. Here, we operate such a device based on a superconducting microwave resonator whose nonlinearity is engineered from kinetic inductance. The device indicates the absorption of low-power microwave wavepackets by transitioning to a self-oscillating state. Using calibrated pulses, we measure the detection efficiency to zeptojoule energy wavepackets. We then apply it to measurements of electron spin resonance, using an ensemble of <sup>209</sup>Bi donors in silicon that are inductively coupled to the resonator. We achieve a latched readout of the spin signal with an amplitude that is five hundred times greater than the underlying spin echoes.