Analyzing the Toffoli gate in disordered circuit QED

TL;DR

This paper investigates how imperfections and fluctuations in coupling constants affect the fidelity of the Toffoli gate in circuit QED, proposing a robust optimization method to improve gate performance under noise.

Contribution

It introduces a quantum control approach that accounts for both static and dynamic imperfections to enhance the robustness of the Toffoli gate in circuit QED.

Findings

Robust Toffoli gate achieved through weighted average fidelity optimization.

Imperfections cause fidelity fluctuations, mitigated by the proposed method.

Enhanced gate performance under realistic noise conditions.

Abstract

We study the effects of imperfections on the fidelity of the Toffoli gate recently realized in a circuit~QED setup using quantum control methods. The noise is introduced in the interqubits interactions. The coupling constants are no longer fixed; instead, they fluctuate around average values obeying some given probability density functions characterizing the dynamical-imperfection case. We also consider the static-imperfection case in which the values of the coupling constants are not exactly known. We obtain a more robust gate by modifying the quantum optimization problem using a weighted average of the fidelity over an interval of coupling values as the objective functional.