A quasiparticle-injection superconducting microwave relaxation oscillator

TL;DR

This paper introduces a superconducting microwave relaxation oscillator, the QUISTRON, which uses quasiparticle injection to achieve tunable GHz-range oscillations with low energy dissipation, suitable for quantum and microwave applications.

Contribution

The paper presents a novel superconducting oscillator design utilizing quasiparticle injection for frequency control, demonstrating tunable GHz oscillations with low power dissipation.

Findings

Oscillation frequency between 1 GHz and 10 GHz.

Energy dissipation per cycle of approximately 100 zJ.

Device operation demonstrated across temperatures from 20 mK to 1 K.

Abstract

We propose a superconducting microwave relaxation oscillator based on a nanowire shunted by a resistor and an inductor controlled by quasiparticle injection from a tunnel junction positioned on it: the QUISTRON. This device exhibits relaxation oscillator behavior with DC voltage-controlled frequency tuning and DC current bias. The device frequency is modulated via the tunnel junction, which induces localized heating by injecting quasiparticles. This heating mechanism modulates the nanowire switching current, enabling relaxation oscillations when it falls below the bias current. We demonstrate the device operating principles and characterize its performance across various parameters, including different choices of shunt resistor, shunt inductance, and bath temperature ranging from 20 mK to 1 K. The device showed oscillation with a frequency range approximately between 1 GHz and 10 GHz and total energy dissipation per cycle of $\sim100$ zJ. Our results suggest that this design offers a promising platform for compact, tunable superconducting oscillators in the microwave spectrum with potential applications in quantum information processing, microwave technology, and ultra-low-power electronics. The straightforward frequency control mechanism and integration potential make this device an attractive candidate for superconducting microwave local oscillators.