DC-powered superconducting microwave amplifiers based on inelastic Cooper-pair tunnelling*

Josephson parametric amplifiers have played a crucial role in improving fidelity of qubit readouts, observation of quantum jumps, quantum feedback algorithms and weak measurements. However, a strong AC pump tone is required for the operation of these amplifiers incurring an overhead of resources in dilution refrigerators. Moreover, there is possibility of cross interactions of this pump tone with other parts of a quantum circuit. In our lab, we work on DC-powered microwave amplifiers based on inelastic Cooper-pair tunnelling (ICTA). We have already demonstrated near quantum-limited amplification with ICTAs. Our goal now is to increase gain-bandwidth product using advanced impedance engineering techniques.