Entangled microwave photons form a fundamental resource for quantum information processing and sensing with continuous variables. We use a low-loss Josephson metamaterial comprising superconducting, nonlinear, asymmetric inductive elements to generate frequency-entangled photons from vacuum fluctuations at a rate of 2 giga entangled bits per second spanning over the 4-GHz bandwidth. The device is operated as a traveling-wave parametric amplifier under Kerr-relieving biasing conditions. Furthermore, we demonstrate single-mode squeezing in such devices—$3.1\pm 0.7\mathrm{dB}$ below the zero-point level at half of modulation frequency.

• Received 5 June 2021
• Revised 6 July 2022
• Accepted 18 July 2022

DOI:https://doi.org/10.1103/PhysRevApplied.18.024063