High-Efficiency, Low-Loss Floquet-mode Traveling Wave Parametric Amplifier

Advancing fault-tolerant quantum computing and fundamental science necessitates quantum-limited amplifiers with near-ideal quantum efficiency and multiplexing capability. However, existing solutions typically achieve one at the expense of the other. In this work, we experimentally demonstrate the first Floquet-mode traveling-wave parametric amplifier (Floquet TWPA), which achieves nearly quantum-limited noise performance, minimal dissipation, and broadband operation, breaking the presumption that broadband amplifiers introduce higher noise. We achieve a system measurement efficiency of $65.1\pm5.8\%$ when measuring a superconducting qubit, which to our knowledge is the highest-reported in a superconducting qubit readout experiment utilizing phase-preserving amplifiers. Our device exhibits $>20$-dB amplification over a $3$-GHz instantaneous bandwidth, $<\!0.5\,$-dB average in-band insertion loss, and the highest reported intrinsic quantum efficiency for a TWPA of $92.1\pm7.6\%$, relative to an ideal phase-preserving amplifier. Fabricated in a superconducting qubit process, these general-purpose Floquet TWPAs are suitable for fast, high-fidelity multiplexed readout in large-scale quantum systems and future monolithic integration with quantum processors.