Controllable coupling between flux qubits

TL;DR

This paper presents a practical method to controllably couple flux qubits using a time-dependent magnetic flux, enabling quantum gate operations and state measurement without fast flux changes.

Contribution

It introduces a novel approach to control qubit coupling via TDMF, avoiding rapid flux adjustments and facilitating quantum logic gates and measurements.

Findings

Effective coupling achieved with TDMF at specific frequencies

Method allows for implementation of quantum gates

Enables flux qubit state tomography

Abstract

We propose an experimentally realizable method to control the coupling between two flux qubits. In our proposal, the bias fluxes are always fixed for these two inductively-coupled qubits. The detuning of these two qubits can be initially chosen to be sufficiently large, so that their initial interbit coupling is almost negligible. When a time-dependent magnetic flux (TDMF) is applied to one of the qubits, a well-chosen frequency of the TDMF can be used to compensate the initial detuning and to couple two qubits. This proposed method avoids fast changes of either qubit frequencies or the amplitudes of the bias magnetic fluxes through the qubit loops, and also offers a remarkable way to implement any logic gate as well as tomographically measure flux qubit states.