Improved coherence in optically defined niobium trilayer-junction qubits

Journal Article · Fri Feb 23 00:00:00 UTC 2024 · Phys.Rev.Applied

DOI: https://doi.org/10.1103/PhysRevApplied.21.024047 · OSTI ID:1988509

Anferov, Alexander ^[1]; Lee, Kan-Heng ^[1]; Zhao, Fang  ^[2]; Simon, Jonathan ^[3]; Schuster, David I. ^[4]

---

1. Chicago U., EFI; Chicago U.
2. Chicago U.; Fermilab
3. Chicago U., EFI; Chicago U.; Stanford U., Phys. Dept.; Stanford U., Appl. Phys. Dept.; SLAC
4. Chicago U., EFI; Chicago U.; Stanford U., Appl. Phys. Dept.; SLAC

Niobium offers the benefit of increased operating temperatures and frequencies for Josephson junctions, which are the core component of superconducting devices. However existing niobium processes are limited by more complicated fabrication methods and higher losses than now-standard aluminum junctions. Combining recent trilayer fabrication advancements, methods to remove lossy dielectrics and modern superconducting qubit design, we revisit niobium trilayer junctions and fabricate all-niobium transmons using only optical lithography. We characterize devices in the microwave domain, measuring coherence times up to $$62~\mu$$s and an average qubit quality factor above $10^5$: much closer to state-of-the-art aluminum-junction devices. We find the higher superconducting gap energy also results in reduced quasiparticle sensitivity above $0.16~$K, where aluminum junction performance deteriorates. Our junction process is readily applied to standard optical-based foundry processes, opening new avenues for direct integration and scalability, and paves the way for higher-temperature and higher-frequency quantum devices.

• Research Organization: Chicago U.; Chicago U., EFI; Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States); SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States); Stanford U., Appl. Phys. Dept.; Stanford U., Phys. Dept.
• Sponsoring Organization: National Science Foundation (NSF); US Department of Energy; USDOE; USDOE Office of Science (SC), High Energy Physics (HEP)
• Grant/Contract Number: 89243024CSC000002; AC02-07CH11359; AC02-76SF00515
• OSTI ID: 1988509
• Report Number(s): FERMILAB-PUB-23-330-ETD; oai:inspirehep.net:2667638; arXiv:2306.05883
• Journal Information: Phys.Rev.Applied, Journal Name: Phys.Rev.Applied Journal Issue: 2 Vol. 21
• Country of Publication: United States
• Language: English