A tunable coupler with ScS quantum point contact to mediate strong interaction between flux qubits

TL;DR

This paper introduces a superconducting quantum coupler using ScS quantum point contact that enables tunable, strong Ising-type interactions between flux qubits, promising for quantum computing and fundamental quantum studies.

Contribution

It proposes a novel tunable quantum inductance coupler based on ScS contact, capable of providing large, adjustable inter-qubit interactions in superconducting quantum circuits.

Findings

Achieves large inter-qubit interaction energies (~1 K)

Demonstrates tunability via external magnetic flux

Analyzes entanglement as a function of interaction strength

Abstract

In this paper we propose a kind of quantum inductance couplers (QUINC) which represents a superconducting loop closed by ScS quantum point contact, operating in deep quantum low-temperature regime to provide tunable (Ising-type) ZZ interaction between flux qubits. This coupler is shown to be well tunable by an external control magnetic flux and to provide large inter-qubit interaction energies $|J/k_{\rm B}|\simeq1$ K thus being very promising as a qubit-coupling device in a quantum register as well as for studying fundamental low-temperature quantum phenomena. Some entanglement measures of a two-qubit system are analyzed as functions of inter-qubit interaction strength.