Flux Qubit in Charge-Phase Regime

TL;DR

This paper proposes a superconducting flux qubit that combines charge and phase degrees of freedom, offering enhanced protection against dephasing and improved readout and coupling capabilities.

Contribution

It introduces a novel flux qubit design utilizing superpositions of flux states with charge-based readout and noise cancellation at the optimal working point.

Findings

Superpositions of flux states form the qubit basis.

Charge degree of freedom enables effective readout and coupling.

First order coupling to charge and flux fluctuations is canceled at the optimal point.

Abstract

A superconducting qubit implementation is proposed that takes the advantage of both charge and phase degrees of freedom. Superpositions of flux states in a superconducting loop with three Josephson junctions form the states of the qubit. The charge degree of freedom is used to readout and couple the qubits. Cancellation of first order coupling to charge and flux fluctuations, at the working point of the qubit, protects it from the dephasing due to these sources.