Comparison of Nb and Ta Pentoxide Loss Tangents for Superconducting Quantum Devices

Journal Article · Fri Dec 05 00:00:00 EST 2025 · No journal information

OSTI ID:3023422

Goronzy, D. P. ^[1]; Mah, W. W. ^[1]; Lim, P. G. ^[1]; Guess, T. ^[2]; Majumder, S. ^[1]; Garcia-Wetten, D. A. ^[1]; Walker, M. J. ^[1]; Ramirez, J. ^[2]; Syong, W.-R. ^[2]; Bennett, D. ^[3]; Vissers, M. ^[3]; dos Reis, R. ^[1]; Pham, T. ^[4]; Dravid, V. P. ^[1]; Hersam, M. C. ^[1]; Bedzyk, M. J. ^[1]; McRae, C. R.H. ^[2]

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1. Northwestern U.
2. NIST, Boulder; Colorado U.
3. NIST, Boulder
4. Northwestern U.; Virginia Tech.

Superconducting transmon qubits are commonly made with thin-film Nb wiring, but recent studies have shown increased performance with Ta wiring. In this work, we compare the resonator-induced single photon, millikelvin dielectric loss for pentoxides of Nb (Nb2O5) and Ta (Ta2O5) in order to further understand limiting losses in qubits. Nb and Ta pentoxides of three thicknesses are deposited via pulsed laser deposition onto identical coplanar waveguide resonators. The two-level system (TLS) loss in Nb2O5 is determined to be about 30% higher than that of Ta2O5. This work indicates that qubits with Nb wiring are affected by higher loss arising from the native pentoxide itself, likely in addition to the presence of suboxides, which are largely absent in Ta.

• Research Organization: Colorado U.; Virginia Tech.; NIST, Boulder; Northwestern U.
• Sponsoring Organization: US Department of Energy
• DOE Contract Number: 89243024CSC000002
• OSTI ID: 3023422
• Report Number(s): FERMILAB-PUB-25-1007-SQMS-V; oai:inspirehep.net:3089831; arXiv:2512.05407
• Journal Information: No journal information, Journal Name: No journal information
• Country of Publication: United States
• Language: English