Mitigation of noise in Josephson parametric oscillator by injection locking

TL;DR

This paper demonstrates that injection locking effectively suppresses phase noise in a Josephson parametric oscillator, stabilizing its output phase and reducing switching-induced noise, which enhances oscillator performance.

Contribution

It provides the first spectroscopic analysis of how injection locking reduces phase noise in a Josephson parametric oscillator, showing the transition from bistable switching to phase stabilization.

Findings

Phase noise is significantly suppressed by injection locking.

Output phase becomes pinned to the locking signal at higher strengths.

Switching noise is minimized when the locking signal exceeds a few photons.

Abstract

Injection locking is a well-established technique widely used in optics as well as solid-state devices for efficient suppression of noise. We present the spectroscopic characterization of the effect of the injection-locking signal (ILS) in mitigating the phase noise of a Josephson parametric oscillator (JPO), whose output oscillating phase undergoes indeterministic switching between the bistable states with symmetry $\theta \rightarrow{\theta+\pi}$. With the injection of a weak locking signal, we measure the phase noise power spectral density of the self-sustained oscillator output state for different locking signal strengths. We observed suppression of phase noise by injection locking. As the ILS strength surpasses more than a few photons, the output state stays completely pinned to the locking phase of the ILS, and the random telegraphic noise due to the switching of the states is significantly suppressed.