Single-Mode Squeezing Using Degenerate Four-Wave Mixing in a Dual-Pump TWPA

Abstract

Single-mode squeezing of the electromagnetic vacuum is a key resource for mode-selective noise reduction in quantum measurements. At microwave frequencies, single-mode squeezing is typically obtained by using Josephson and Traveling-Wave Parametric Amplifiers designed for three-wave mixing operation. In single-pump degenerate four-wave mixing, the coincidence of pump, signal, and idler frequencies complicates separation of the squeezed field from the strong pump. A dual-pump configuration enables degenerate operation while keeping both pumps spectrally separated from the squeezed mode. Here, we demonstrate single-mode squeezing in a flux-tunable, dual-pump Traveling-Wave Parametric Amplifier, employing reversed-Kerr phase matching. By independently calibrating the single-pump gains, we find that the strongest squeezing occurs along approximately balanced-gain trajectories, while the optimal squeezing does not necessarily correspond to the highest dual-pump gain. At flux biases $Φ_\mathrm{ext}/Φ_0 = 0.0$ and $0.5$, the minimum quadrature noise levels reach $-2.48 \pm 0.18~\mathrm{dB}$ and $-1.62 \pm 0.20~\mathrm{dB}$ relative to vacuum, respectively. These results establish the proposed architecture as a platform for single-mode squeezing in microwave continuous-variable quantum technologies.