Tunable coupling of superconducting qubits

TL;DR

This paper explores a tunable coupling mechanism for superconducting qubits using a current-biased Josephson junction as an LC-circuit, enabling controlled entanglement and two-qubit operations.

Contribution

It introduces a method to tune qubit coupling via a CBJJ, allowing flexible entanglement control across different qubit designs.

Findings

Tunable coupling achieved by modulating bias current.

Effective two-qubit operations demonstrated.

Applicable to various superconducting qubit types.

Abstract

We study an LC-circuit implemented using a current-biased Josephson junction (CBJJ) as a tunable coupler for superconducting qubits. By modulating the bias current, the junction can be tuned in and out of resonance and entangled with the qubits coupled to it. One can thus implement two-qubit operations by mediating entanglement. We consider the examples of CBJJ and charge--phase qubits. A simple recoupling scheme leads to a generalization to arbitrary qubit designs.