Suppression of Tunneling in a Superconducting Persistent-Current Qubit

TL;DR

This paper demonstrates how to completely suppress tunneling in a superconducting persistent-current qubit by tuning magnetic field, Josephson couplings, and offset charges, using interference effects similar to those in magnetic particles.

Contribution

It introduces a method to achieve perfect suppression of tunneling in a superconducting qubit through interference control, a novel approach in quantum circuit design.

Findings

Tunneling can be fully suppressed by tuning system parameters.

Suppression is due to interference between tunneling paths.

The effect is analogous to phenomena in magnetic particles with half-integer spin.

Abstract

We consider a superconducting persistent-current qubit consisting of a three-junction superconducting loop in an applied magnetic field. We show that by choosing the field, Josephson couplings, and offset charges suitably, we can perfectly suppress the tunneling between two oppositely directed states of circulating current, leading to a vanishing of the splitting between the two qubit states. The suppression arises for interference between tunneling along different paths, and is analogous to that predicted previously for magnetic particles with half-integer spin.