Tunable coupling scheme for flux qubits at the optimal point

TL;DR

This paper proposes a practical, tunable coupling scheme for flux qubits that maintains optimal points for coherence and is suitable for scalable quantum computing, enhancing two-qubit gate implementation.

Contribution

It introduces a tunable coupling method using quantum inductance of a third qubit, remaining at optimal points for coherence and noise insensitivity.

Findings

Coupling scheme remains at optimal points for coherence.

Design is compatible with microwave-induced parametric coupling.

Scheme is experimentally feasible and extendable to multiqubit systems.

Abstract

We discuss a practical design for tunably coupling a pair of flux qubits via the quantum inductance of a third high-frequency qubit. The design is particularly well suited for realizing a recently proposed microwave-induced parametric coupling scheme. This is attractive because the qubits can always remain at their optimal points. Furthermore, we will show that the resulting coupling also has an optimal point where it is insensitive to low-frequency flux noise. This is an important feature for the coherence of coupled qubits. The presented scheme is an experimentally realistic way of carrying out two-qubit gates and should be easily extended to multiqubit systems.