Parametric amplification and squeezing with an ac- and dc-voltage biased superconducting junction

TL;DR

This paper proposes a theoretical model for a superconducting junction-based parametric amplifier that uses combined ac and dc voltages to achieve high gain and squeezing, with tunable performance and broad bandwidth.

Contribution

It introduces a novel superconducting junction amplifier design leveraging quasiparticle dynamics and photon-assisted tunneling for enhanced, tunable quantum-limited amplification and squeezing.

Findings

Over 20 dB phase-sensitive microwave amplification

Broadband phase-preserving amplification of 20 dB over 1.2 GHz

Single- and two-mode squeezing exceeding -12 dB over 5.3 GHz

Abstract

We theoretically investigate a near-quantum-limited parametric amplifier based on the nonlinear dynamics of quasiparticles flowing through a superconducting-insulator-superconducting junction. Photon-assisted tunneling, resulting from the combination of dc- and ac-voltage bias, gives rise to a strong parametric interaction for the electromagnetic modes reflected by the junction coupled to a transmission line. We show phase-sensitive and phase-preserving amplification, together with single- and two-mode squeezing. For an aluminum junction pumped at twice the center frequency, $\omega_0/2\pi=6$~GHz, we predict narrow-band phase-sensitive amplification of microwaves signals to more than 20 dB, and broadband phase-preserving amplification of 20 dB over a 1.2 GHz 3-dB bandwidth. We also predict single- and two-mode squeezing reaching more than -12 dB over 5.3 GHz 3-dB bandwidth. Moreover, with a simple impedance matching circuit, we demonstrate 3 dB bandwidth reaching 4.3 GHz for 20 dB of gain. A key feature of the device is that its performance can be controlled in-situ with the applied dc- and ac-voltage biases.