Nonreciprocal Josephson Traveling-Wave Parametric Amplifiers

Superconducting parametric amplifiers have been routinely used as preamplifiers to enable fast, high-fidelity qubit readout. However, isolation is required to prevent the reflected pump and amplified vacuum from dephasing the qubits. Using commercial bulk magnetic isolators before preamplification does so at the cost of additional insertion loss and off-chip cabling, limiting the system measurement efficiency and amplifier on-chip integration. In this work, we present a type of Josephson traveling-wave parametric amplifier design capable of achieving broadband parametric gain and reverse isolation at the same time. We present numerical simulation results and preliminary characterization of the fabricated device.