Auxiliary Microwave Circuit for Broadband Josephson Parametric Amplifier for Multiplexing Qubit Readout

We introduce an auxiliary microwave circuit which expands the bandwidth of a Josephson parametric amplifier(JPA) by transforming its coupling impedance to the environment. A conventional JPA shows a few tens of MHz bandwidth that is not sufficient to perform multi-qubit controls. Previous study reported the broadening of the bandwidth by coupling a JPA strongly with the environment thorough an impedance reducing circuit that lowers its loaded quality factor.[1] Besides, the introduction of frequency dependent coupling impedance, which behaves as an LC resonator, expands the bandwidth further.[2] Here we optimized the parameters in various types of impedance transforming circuits designed to obtain the stable performance with extended bandwidth. We will test and verify various types of the auxiliary circuits experimentally for the most desirable performance of a broadband JPA.

[1] Mutus, J. Y., et al. (2014). Strong environmental coupling in a Josephson parametric amplifier. Applied Physics Letters, 104(26).

[2] Roy, T., et al. (2015). Broadband parametric amplification with impedance engineering: Beyond the gain-bandwidth product. Applied Physics Letters, 107(26).