Field Programmable Josephson Amplifier for non-reciprocal microwave signal processing
Florent Q. Lecocq, Leonardo Ranzani, Gabriel A. Peterson, Katarina Cicak, Raymond W. Simmonds, John D. Teufel, Jose A. 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 in-situ by a set of microwave drives to perform reciprocal and non-reciprocal frequency conversion and amplification. In this work we demonstrate four modes of operation: frequency conversion (90% transmission, 0.1% reflection), circulation (90% transmission, 0.1% reflection, 30dB isolation), phase-preserving amplification (gain >20dB, 1 photon of added noise) and directional phase-preserving amplification (5% reflection, 18dB forward gain, 10dB 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 towards on-chip integration with superconducting quantum circuits such as qubits or microwave optomechanical systems.