Time-optimal performance of Josephson charge qubits: A process tomography approach

TL;DR

This paper uses process tomography to optimize Josephson charge qubits, balancing leakage and dephasing, to achieve minimal fidelity loss within current experimental capabilities.

Contribution

It introduces a process tomography-based optimization scheme for Josephson charge qubits, incorporating microscopic modeling and time-optimal control to enhance performance.

Findings

Achieved minimal gate fidelity loss of approximately 10^{-3}

Demonstrated control of qubit-environment interaction reduces decoherence

Provided a practical framework for optimizing superconducting qubits

Abstract

A process tomography based optimization scheme for open quantum systems is used to determine the performance limits of Josephson charge qubits within current experimental means. The qubit is modeled microscopically as an open quantum system taking into account state leakage, as well as environment-induced dephasing based on experimental noise spectra. Within time-optimal control theory, we show that the competing requirements for suppression of state leakage and dephasing can be met by an external control of the effective qubit-environment interaction, yielding minimal gate fidelity losses of around $\Delta F \approx 10^{-3}$ under typical experimental conditions.