Enhancing Dispersive Readout of Superconducting Qubits Through Dynamic Control of the Dispersive Shift: Experiment and Theory

TL;DR

This paper demonstrates an improved superconducting qubit readout method by dynamically controlling the dispersive shift, achieving high fidelity and speed, with strong experimental-theoretical agreement, enhancing quantum computing protocols.

Contribution

It introduces a dynamic control technique to enhance dispersive readout of superconducting qubits, significantly improving fidelity and signal-to-noise ratio compared to previous methods.

Findings

Achieved 0.25% readout error in 100 ns

Nearly quadrupled signal-to-noise ratio

Excellent agreement between experiment and theory

Abstract

The performance of a wide range of quantum computing algorithms and protocols depends critically on the fidelity and speed of the employed qubit readout. Examples include gate sequences benefiting from mid-circuit, real-time, measurement-based feedback, such as qubit initialization, entanglement generation, teleportation, and perhaps most importantly, quantum error correction. A prominent and widely-used readout approach is based on the dispersive interaction of a superconducting qubit strongly coupled to a large-bandwidth readout resonator, frequently combined with a dedicated or shared Purcell filter protecting qubits from decay. By dynamically reducing the qubit-resonator detuning and thus increasing the dispersive shift, we demonstrate a beyond-state-of-the-art two-state-readout error of only $0.25\,\%$ in 100 ns integration time. Maintaining low readout-drive strength, we nearly quadruple the signal-to-noise ratio of the readout by doubling the readout mode linewidth, which we quantify by considering the hybridization of the readout-resonator and its dedicated Purcell-filter. We find excellent agreement between our experimental data and our theoretical model. The presented results are expected to further boost the performance of new and existing algorithms and protocols critically depending on high-fidelity, fast, mid-circuit measurements.