Conceptual

Kinetic Inductance Traveling Wave Parametric Amplifier for Multiplexed Qubit Readout

A kinetic-inductance traveling-wave parametric amplifier (KI-TWPA) uses the current-dependent kinetic inductance of a long disordered-superconductor transmission line to amplify microwave signals near the quantum noise limit over several GHz of bandwidth, making it suited to reading out many superconducting qubits simultaneously. Integrated as the first-stage amplifier and calibrated via ac Stark shift, it improves readout signal-to-noise ratio and state-measurement fidelity over a conventional HEMT chain while keeping added noise to a few quanta.