Tunable Coupling in Circuit Quantum Electrodynamics Using a Superconducting Charge Qubit with a<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>V</mml:mi></mml:math>-Shaped Energy Level Diagram

TLDR

Recent progress in superconducting qubits shows promise for quantum information processing, and independent control of qubit interactions and energies is a desirable feature. The study introduces a superconducting charge qubit with a V‑shaped energy spectrum that enables independent control of qubit energy and dipole coupling via quantum interference. This is achieved by employing quantum interference in the qubit design to decouple energy and coupling, allowing tunable interaction with a superconducting cavity. Dynamic tuning of the coupling strength from <200 kHz to >40 MHz demonstrates access to the strong coupling regime, enabling protection from cavity‑induced relaxation and avoidance of unwanted qubit–qubit interactions.

Abstract

Recent progress in superconducting qubits has demonstrated the potential of these devices for the future of quantum information processing. One desirable feature for quantum computing is independent control of qubit interactions as well as qubit energies. We demonstrate a new type of superconducting charge qubit that has a V-shaped energy spectrum and uses quantum interference to provide independent control over the qubit energy and dipole coupling to a superconducting cavity. We demonstrate dynamic access to the strong coupling regime by tuning the coupling strength from less than 200 kHz to more than 40 MHz. This tunable coupling can be used to protect the qubit from cavity-induced relaxation and avoid unwanted qubit-qubit interactions in a multi-qubit system.