Operation of a high-frequency, phase-slip qubit
Cheeranjeev Purmessur, Kaicheung Chow, Bernard van Heck, Angela Kou · Nature Communications · 2025
Aluminum-based Josephson junctions are currently the main sources of nonlinearity for control and manipulation of superconducting qubits. A constriction-based junction provides an alternative source of nonlinearity that promises new types of protected qubits and the possibility of high-temperature and high-frequency operation through the use of superconductors with larger energy gaps. Junctions made from such superconductors have been challenging to incorporate into superconducting qubits because of difficulty controlling junction parameters and have had extremely low lifetimes, which limited their utility. Here we demonstrate that junctions made using titanium nitride (TiN) are a promising and controllable qubit platform. We use TiN junctions to build superconducting qubits based on quantum phase slips through the junction. We operate the qubit at zero flux where the qubit frequency ( ~ 17GHz) is mainly determined by the inductance of the qubit. We perform readout and coherent control of the superconducting qubit, and measure qubit lifetimes >60μs. Finally, we demonstrate operation of the qubit at temperatures exceeding 300 mK. Our results add the TiN-based junction as a tool for superconducting quantum information processing and opens avenues for new classes of superconducting qubits. Superconducting constrictions are an alternative source of nonlinearity to Al-based Josephson junctions, enabling new functionalities for qubits. Here, the authors demonstrate a high-frequency superconducting qubit in a single TiN thin film, based on coherent quantum phase slip tunneling through a constriction.