Coupling of Josephson current qubits using a connecting loop

TL;DR

This paper introduces a novel coupling scheme for three-Josephson junction qubits using a connecting loop, enabling large, tunable level splitting for efficient CNOT operations suitable for fault-tolerant quantum computing.

Contribution

It proposes a new coupling method that avoids mutual inductance, with calculable coupling strength based on junction energy and loop length, advancing scalable quantum computing design.

Findings

The scheme achieves large, tunable level splitting.

The CNOT gate meets fault-tolerance criteria.

Coupling strength depends on junction energy and loop length.

Abstract

We propose a coupling scheme for the three-Josephson junction qubits which uses a connecting loop, but not mutual inductance. Present scheme offers the advantages of a large and tunable level splitting in implementing the controlled-NOT (CNOT) operation. We calculate the switching probabilities of the coupled qubits in the CNOT operations and demonstrate that present CNOT gate can meet the criteria for the fault-tolerant quantum computing. We obtain the coupling strength as a function of the coupling energy of the Josephson junction and the length of the connecting loop which varies with selecting two qubits from the scalable design.