Double-Well Potentials in Current Qubits

TL;DR

This paper investigates new periodic double-well potentials with cusp barriers in superconducting qubits, showing that these potentials can enhance tunneling and potentially improve qubit performance.

Contribution

It introduces a novel class of cusp-shaped double-well potentials in current qubits, derived from the phase boundary conditions, and analyzes their tunneling properties.

Findings

Cusp barriers alter tunneling dynamics in superconducting qubits.

Large inductance and Josephson energy favor cusp potential formation.

Cusp potentials may lead to more efficient qubit operation.

Abstract

The effective potentials of the rf-SQUID and three-Josephson junction loop with a penetrating external magnetic flux are studied. Using the periodic boundary condition for the phase evolution of the wave function of Cooper pairs, we obtain new periodic potentials with cusp barriers in contrast with the usual smooth double-well potential. The tunneling through the cusp barrier becomes dominant for a parameter regime where the self inductance of the superconducting loop and the Josephson coupling energy are large. Calculating the tunneling frequency we see that the cusp potential may offer a more efficient qubit.