Qubit dispersive readout scheme with a microstrip squid amplifier

TL;DR

This paper demonstrates a dispersive readout scheme for flux qubits using a microstrip squid amplifier, achieving low noise performance suitable for quantum computing applications.

Contribution

It introduces a novel dispersive readout method with an in-situ tunable amplifier, enhancing qubit measurement fidelity and noise performance.

Findings

Amplifier noise approaches quantum limit at low temperatures

Two operational regimes identified: crossing and anticrossing

Proof of principle demonstrated with simulated flux changes

Abstract

A flux qubit readout scheme involving a dispersive technique coupled to a microstrip squid amplifier has been tested experimentally. Thanks to the almost quantum limited noise of this amplifier at low temperature, this readout device is very promising for a design with actual qubits. It's proof of principle and low noise performance have been tested by simulating the qubit presence applying a tiny flux change in the input squid. The resonant frequency of the amplifier is adjusted in-situ with a varactor diode to approach the frequency of the tank circuit. Depending on the sign of the transfer function, two operating mode (crossing or anticrossing regime) have been identified.