Dephasing of coupled qubit system during gate operations due to background charge fluctuations

TL;DR

This paper investigates how background charge fluctuations cause dephasing in coupled Josephson charge qubits, affecting gate fidelity, and finds that increased qubit interaction can improve gate accuracy despite these fluctuations.

Contribution

It analyzes the impact of background charge fluctuations on coupled qubits and reveals that stronger qubit interactions can mitigate dephasing effects during gate operations.

Findings

Background charge fluctuations cause gate errors in coupled qubits.

Increased qubit interaction improves gate fidelity despite fluctuations.

Fluctuations affect the diagonal elements of the qubit density matrix.

Abstract

A quantum computer that can be constructed based on a superconducting nanocircuits has previously been proposed. We examine the effect of background charge fluctuations on a coupled Josephson charge qubit system used in such a computer. In previous work, the background charge fluctuations were found to be an important dephasing channel for a single Josephson qubit. We investigate the effect of fluctuations in the bias at the charge degeneracy point of a Josephson charge qubit system. Evaluated quantities are gate fidelity and diagonal elements of the qubit's density matrix. The fluctuation leads to gate error, however quantum gate operation becomes more accurate with increasing interaction between qubit systems.