Nonreciprocal microwave signal processing with a Field-Programmable Josephson Amplifier

  1. F. Lecocq,
  2. L. Ranzani,
  3. G. A. Peterson,
  4. K. Cicak,
  5. R. W. Simmonds,
  6. J. D. Teufel,
  7. and J. Aumentado
We report on the design and implementation of a Field Programmable Josephson Amplifier (FPJA) – a compact and lossless superconducting circuit that can be programmed \textit{in situ} by a set of microwave drives to perform reciprocal and nonreciprocal frequency conversion and amplification. In this work we demonstrate four modes of operation: frequency conversion (−0.5 dB transmission, −30 dB reflection), circulation (−0.5 dB transmission, −30 dB reflection, 30 dB isolation), phase-preserving amplification (gain >20 dB, 1 photon of added noise) and directional phase-preserving amplification (−10 dB reflection, 18 dB forward gain, 8 dB reverse isolation, 1 photon of added noise). The system exhibits quantitative agreement with theoretical prediction. Based on a gradiometric Superconducting Quantum Interference Device (SQUID) with Nb/Al-AlOx/Nb Josephson junctions, the FPJA is first-order insensitive to flux noise and can be operated without magnetic shielding at low temperature. Due to its flexible design and compatibility with existing superconducting fabrication techniques, the FPJA offers a straightforward route toward on-chip integration with superconducting quantum circuits such as qubits or microwave optomechanical systems.
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