Flux-pulse-assisted Readout of a Fluxonium Qubit

TL;DR

This paper proposes a flux-pulse-assisted readout method for fluxonium qubits, demonstrating through simulations that it significantly improves readout speed and accuracy, even under realistic noise and efficiency conditions.

Contribution

It introduces a novel flux-pulse-assisted readout scheme for fluxonium qubits, enhancing readout performance by exploiting dispersive shift features.

Findings

Approximately 5 times improvement in signal-to-noise ratio with 155 ns integration time.

Performance remains robust under flux noise and finite measurement efficiency.

Suitable energy parameters identified for practical implementation.

Abstract

Much attention has focused on the transmon architecture for large-scale superconducting quantum devices, however, the fluxonium qubit has emerged as a possible successor. With a shunting inductor in parallel to a Josephson junction, the fluxonium offers larger anharmonicity and stronger protection against dielectric loss, leading to higher coherence times as compared to conventional transmon qubits. The interplay between the inductive and Josephson energy potentials of the fluxonium qubit leads to a rich dispersive shift landscape when tuning the external flux. Here we propose to exploit the features in the dispersive shift to improve qubit readout. Specifically, we report on theoretical simulations showing improved readout times and error rates by performing the readout at a flux bias point with large dispersive shift. We expand the scheme to include different error channels, and show that with an integration time of 155 ns, flux-pulse-assisted readout offers about 5 times improvement in the signal to noise ratio. Moreover, we show that the performance improvement persists in the presence of finite measurement efficiency combined with quasi-static flux noise, and also when considering the increased Purcell rate at the flux-pulse-assisted readout point. We suggest a set of reasonable energy parameters for the fluxonium architecture that will allow for the implementation of our proposed flux-pulse-assisted readout scheme.