Broadband Squeezed Microwaves and Amplification with a Josephson Traveling-Wave Parametric Amplifier

Abstract

Squeezed light enables precision measurement beyond the standard quantum limit imposed by the Heisenberg uncertainty principle. It has been widely adopted in research fields to achieve scientific breakthroughs from gravitational wave detection to biological microscopy enhancement. The generation of highly-squeezed states using superconducting amplifiers is a foundation for quantum optics and quantum metrology in the microwave domain. In superconducting circuits, researchers commonly use cavity-based Josephson amplifiers to generate squeezed microwaves. These narrow-band squeezers use a resonator and its Q-enhanced circulating field to increase the interaction between photons and a single or few nonlinear elements, but can lead to higher-order nonlinearities that impact squeezing performance. In contrast, a Josephson traveling-wave parametric amplifier (JTWPA) consists of many Josephson junctions in series, effectively distributing the stress on nonlinear elements across the entire amplifier. By eliminating the resonant structure, the JTWPA allows a larger pump current before the junctions become saturated, leading to a higher dynamic range and circumventing the cavity bandwidth constraint. Therefore, JTWPA can generate substantial squeezing with a high dynamic range and emit broadband entangled microwave photons. This thesis will demonstrate non-degenerate four-wave mixing using a dual-dispersion-engineered JTWPA and investigate its squeezing performance.