Switchable resonant coupling of flux qubits

TL;DR

This paper introduces a switchable coupling scheme for flux qubits using a tunable AC magnetic flux, enabling flexible and sign-reversible interactions while maintaining qubits at their degeneracy points.

Contribution

It presents a novel coupling method that allows dynamic control and sign reversal of interactions between flux qubits with different frequencies.

Findings

Coupling can be switched on and off by tuning the flux frequency.

All qubits can be at degeneracy points during coupling.

The coupling sign can be reversed.

Abstract

We propose a coupling scheme, where two or more flux qubits with different eigenfrequencies share Josephson junctions with a coupler loop devoid of its own quantum dynamics. Switchable two-qubit coupling is realized by tuning the frequency of the AC magnetic flux through the coupler to a combination frequency of two of the qubits. The coupling allows any or all of the qubits to be simultaneously at the degeneracy point and can change sign.