Innovative fabrication strategies of high-Coherence Superconducting Qubits

The SQMS Nanofabrication Taskforce unites experts in materials science and nanofabrication, with the mission to advance the development of novel materials, substrates, and fabrication techniques for high coherence superconducting quantum devices. Our ongoing research focus is on strategies aimed at extending qubit coherence times to millisecond scales and beyond.

This poster will provide a systematic study addressing different processing techniques and material characterization: substrate preparation techniques, alternative low-loss materials (Nb, Ta, and Re) substrates as well as different thicknesses, innovative non-oxide forming low-loss capping layers (like proximitized Au, Ta), as well as optimized designs for qubits and Josephson junction materials and design themselves.

The initial results brought from the new process techniques of nanofabrication and material study has demonstrated T1 enhancement by almost an order of magnitude with best T1’s reaching ~ 600 ms. [1]. This was the result of a first coordinated effort of the Taskforce to eliminate the lossy materials at surfaces and interfaces of superconducting qubits to enhance qubit coherence. In fact, the improvement is to be attributed to the replacement of lossy native Nb oxide layer with native Ta oxide, which is thinner and less disordered.

In this presentation we will elaborate and discuss on further enhancements we are implementing in the processing steps for Josephson junctions, as well as the results we have achieved for high-coherence quantum devices with the aforesaid improvements.

This material is based upon work supported by the U.S. Department of Energy, Office of Science, National Quantum Information Science Research Centers, Superconducting Quantum Materials and Systems Center (SQMS) under contract number DE-AC02-07CH11359.

[1] npj Quantum Inf 10, 43 (2024)