Google Research

Josephson parametric circulator with same-frequency signal ports, 200 MHz bandwidth, and high dynamic range

Applied Physics Letters, vol. 122 (2023), pp. 224001


We demonstrate a 3-port Josephson parametric circulator, matched to 50 Ohm using second order Chebyshev networks. The device notably operates with two of its signal ports at the same frequency and uses only two out-of-phase pumps at a single frequency. As a consequence, When operated as an isolator it does not require phase coherence between the pumps and the signal, simplifying the requirements for its integration into standard dispersive qubit readout setups. The device utilizes parametric couplers based on a balanced bridge of rf-SQUID arrays, which offer purely parametric coupling and high dynamic range. We characterize the device by measuring its full 3x3 S-matrix as a function of frequency the relative phase between the two pumps. We find up to 15 dB nonreciprocity over a 200 MHz signal band, port match better than 10 dB, low insertion loss of 0.6 dB, and saturation power exceeding -80 dBm.

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