Tunable coupling of qubits: nonadiabatic corrections

TL;DR

This paper investigates the effects of nonadiabatic corrections on tunable qubit coupling, revealing their significance and persistence even when the coupling is tuned to zero, with implications for quantum control.

Contribution

It provides an analysis of nonadiabatic effects in tunable qubit coupling, extending understanding beyond the adiabatic approximation in quantum systems.

Findings

Nonadiabatic corrections are significant and can dominate in certain parameter regimes.

Inductive contributions persist even when capacitive coupling is tuned to zero.

Total coupling can be effectively turned off at symmetry points in the qubits.

Abstract

We analyze the coupling of qubits mediated by a tunable and fast element beyond the adiabatic approximation. The nonadiabatic corrections are important and even dominant in parts of the relevant parameter range. As an example, we consider the tunable capacitive coupling between two charge qubits mediated by a gated Josephson junction, as suggested by Averin and Bruder. The nonadiabatic, inductive contribution persists when the capacitive coupling is tuned to zero. On the other hand, the total coupling can be turned off (in the rotating wave approximation) if the qubits are operated at symmetry points.