Flux-driven impedance-matched Josephson parametric amplifier with improved pump efficiency*

Impedance-matched Josephson parametric amplifiers (IMPAs) with the instantaneous bandwidth of several hundred MHz are crucial for frequency-multiplexed dispersive readout of superconducting qubits. However, for further integration of qubits, required pump power for such amplifiers can be a concern, since a high pump power may result in the increase of refrigerator temperature as well as the degradation of qubit performance due to pump leakage. In this presentation, we experimentally demonstrate highly improved pump efficiency of flux-driven IMPAs by adding two features to their pump structures: (i) kinetic-inductance coupling between the SQUID in the amplifiers and pump waveguide [1] and (ii) a low-Q resonator to store pump photons and enhance the parametric process. Owing to these improvements, we can operate a flux-driven IMPA at about 20-dB gain in a nearly 1-GHz bandwidth with a pump power less than -60 dBm at base temperature, which is hundred times smaller compared with our previous device [2].

[1] C. W. Sandbo Chang et al., Phys. Rev. X 10, 011011 (2020).
[2] Y. Urade et al., APS March Meeting 2020, J07.00005.