High-Fidelity Readout in Circuit Quantum Electrodynamics Using the Jaynes-Cummings Nonlinearity

TL;DR

This paper introduces a high-fidelity qubit readout method in circuit QED that leverages the Jaynes-Cummings nonlinearity, achieving over 87% single-shot fidelity and effective multi-qubit correlation measurements.

Contribution

It presents a novel measurement protocol exploiting the nonlinear response of a superconducting cavity, improving qubit readout fidelity with standard experimental setups.

Findings

Achieved 87% single-shot fidelity in qubit readout.

Observed a high-transmission 'bright' state at a critical power.

Demonstrated at least 61% fidelity in joint three-qubit correlations.

Abstract

We demonstrate a qubit readout scheme that exploits the Jaynes-Cummings nonlinearity of a superconducting cavity coupled to transmon qubits. We find that in the strongly-driven dispersive regime of this system, there is the unexpected onset of a high-transmission "bright" state at a critical power which depends sensitively on the initial qubit state. A simple and robust measurement protocol exploiting this effect achieves a single-shot fidelity of 87% using a conventional sample design and experimental setup, and at least 61% fidelity to joint correlations of three qubits.