Controllable Coupling between Flux Qubits

Yu-Xi Liu,Franco Nori,J S Tsai,L F Wei

doi:10.1103/physrevlett.96.067003

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 variable frequency or 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.

Highlights

We propose an experimentally realizable method to control the coupling between two flux qubits
The switching time of the magnetic flux should be less than the inverse single-qubit Josephson energy, which is a challenge for present experiments
Here, the two-qubit coupling and decoupling are controlled by the frequency of the applied time-dependent magnetic flux (TDMF)

Summary

Introduction

We propose an experimentally realizable method to control the coupling between two flux qubits. The bias fluxes are always fixed for these two inductively coupled qubits. Entangled macroscopic quantum states have been experimentally verified in systems of coupled flux [3], and phase [4,5] qubits.

Results

Conclusion