Discovering new platforms for high coherence qubits using direct materials characterization*

Many platforms for quantum technologies are limited by noise and loss arising from uncontrolled defects at surfaces and interfaces, including superconducting qubits, color centers in diamond, trapped ions, and semiconductor quantum dots. I will describe our recent efforts to tackle noise and microwave losses in superconducting qubits. Building large, useful quantum systems based on transmon qubits will require significant improvements in qubit relaxation and coherence times, which are orders of magnitude shorter than limits imposed by bulk properties of the constituent materials. This indicates that relaxation likely originates from uncontrolled surfaces, interfaces, and contaminants. Previous efforts to improve qubit lifetimes have focused primarily on designs that minimize contributions from surfaces. However, significant improvements in the lifetime of two-dimensional transmon qubits have remained elusive for several years. We have fabricated two-dimensional transmon qubits that have both lifetimes and coherence times with dynamical decoupling exceeding 0.3 milliseconds by replacing niobium with tantalum in the device [1]. We have observed increased lifetimes for many devices, indicating that these material improvements are robust, paving the way for higher gate fidelities in multi-qubit processors.


[1] A. P. M. Place, L. V. H. Rodgers, P. Mundada, B. M. Smitham, M. Fitzpatrick, Z. Leng, A. Premkumar, J. Bryon, S. Sussman, G. Cheng, T. Madhavan, H. K. Babla, B. Jaeck, A. Gyenis, N. Yao, R. J. Cava, N. P. de Leon, A. A. Houck, "New material platform for superconducting transmon qubits with coherence times exceeding 0.3 milliseconds," arXiv:2003.00024.