Low-decoherence flux qubit

TL;DR

This paper proposes a modified flux qubit design with a shunt capacitor that significantly reduces decoherence caused by noise, especially away from the degeneracy point, enhancing qubit performance.

Contribution

Introducing a shunt capacitor in flux qubits to suppress noise effects and extend coherence times beyond the degeneracy point.

Findings

Decoherence is reduced by decreasing Josephson junction coupling energy.

Increasing shunt capacitance further suppresses noise effects.

The modified design offers improved qubit stability and coherence.

Abstract

A flux qubit can have a relatively long decoherence time at the degeneracy point, but away from this point the decoherence time is greatly reduced by dephasing. This limits the practical applications of flux qubits. Here we propose a new qubit design modified from the commonly used flux qubit by introducing an additional capacitor shunted in parallel to the smaller Josephson junction (JJ) in the loop. Our results show that the effects of noise can be considerably suppressed, particularly away from the degeneracy point, by both reducing the coupling energy of the JJ and increasing the shunt capacitance. This shunt capacitance provides a novel way to improve the qubit.