Stability of longitudinal coupling for Josephson charge qubits

TL;DR

This paper investigates the conditions under which longitudinal coupling in inductively coupled superconducting charge qubits remains stable against parameter variations and control field fluctuations, enhancing qubit coherence.

Contribution

It identifies parameter regimes where longitudinal coupling commutes with single-qubit terms and demonstrates its stability against circuit and control fluctuations.

Findings

Longitudinal coupling can be stabilized in specific parameter regimes.

Coupling commutes with single-qubit terms under certain conditions.

Stability against fluctuations improves qubit coherence.

Abstract

For inductively coupled superconducting quantum bits, we determine the conditions when the coupling commutes with the single-qubit terms. We show that in certain parameter regimes such longitudinal coupling can be stabilized with respect to variations of the circuit parameters. In addition, we analyze its stability against fluctuations of the control fields.