Readout of a Quantum Processor with High Dynamic Range Josephson Parametric Amplifiers

Josephson parametric amplifiers are a key technology in superconducting quantum computation as they allow for fast accurate measurement of qubit states with dispersive microwave readout. For larger quantum processors, size constraints will require frequency multiplexed readout of many tones on a single line. Traveling wave parametric amplifiers provide large bandwidth and high saturation power, but are difficult to fabricate and have higher internal loss. Lumped element amplifiers can provide high quantum efficiency and large bandwidth, but have traditionally been limited to input powers of less than -115 dBm at 20 dB gain. Here, we demonstrate that by replacing the dc-SQUID in our impedance-matched parametric amplifiers with an rf-SQUID array, we can achieve an over 100-fold increase in saturation power. We discuss the design and characterization of these amplifiers and present data measured using a 54-qubit Sycamore processor. We show these amplifiers can easily support simultaneous readout of up to 6 tones with no loss of efficiency due to saturation.