Systematic improvements in transmon qubit coherence enabled by niobium surface encapsulation

Mustafa Bal; Akshay A. Murthy; Shaojiang Zhu; Francesco Crisa; Xinyuan You; Ziwen Huang; Tanay Roy; Jaeyel Lee; David van Zanten; Roman Pilipenko; Ivan Nekrashevich; Andrei Lunin; Daniel Bafia; Yulia Krasnikova; Cameron J. Kopas; Ella O. Lachman; Duncan Miller; Josh Y. Mutus; Matthew J. Reagor; Hilal Cansizoglu; Jayss Marshall; David P. Pappas; Kim Vu; Kameshwar Yadavalli; Jin Su Oh; Lin Zhou; Matthew J. Kramer; Florent Lecocq; Dominic P. Goronzy; Carlos G. Torres-Castanedo; P. Graham Pritchard; Vinayak P. Dravid; James M. Rondinelli; Michael J. Bedzyk; Mark C. Hersam; John Zasadzinski; Jens Koch; James A. Sauls; Alexander Romanenko; Anna Grassellino

doi:10.1038/s41534-024-00840-x

Systematic improvements in transmon qubit coherence enabled by niobium surface encapsulation

Mustafa Bal, Akshay A. Murthy, Shaojiang Zhu, Francesco Crisa, Xinyuan You, Ziwen Huang, Tanay Roy, Jaeyel Lee, David van Zanten, Roman Pilipenko, Ivan Nekrashevich, Andrei Lunin, Daniel Bafia, Yulia Krasnikova, Cameron J. Kopas, Ella O. Lachman, Duncan Miller, Josh Y. Mutus, Matthew J. Reagor, Hilal CansizogluJayss Marshall, David P. Pappas, Kim Vu, Kameshwar Yadavalli, Jin Su Oh, Lin Zhou, Matthew J. Kramer, Florent Lecocq, Dominic P. Goronzy, Carlos G. Torres-Castanedo, P. Graham Pritchard, Vinayak P. Dravid, James M. Rondinelli, Michael J. Bedzyk, Mark C. Hersam, John Zasadzinski, Jens Koch, James A. Sauls, Alexander Romanenko^*, Anna Grassellino^*

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

4 Scopus citations

Abstract

We present a transmon qubit fabrication technique that yields systematic improvements in T₁ relaxation times. We encapsulate the surface of niobium and prevent the formation of its lossy surface oxide. By maintaining the same superconducting metal and only varying the surface, this comparative investigation examining different capping materials, such as tantalum, aluminum, titanium nitride, and gold, as well as substrates across different qubit foundries demonstrates the detrimental impact that niobium oxides have on coherence times of superconducting qubits, compared to native oxides of tantalum, aluminum or titanium nitride. Our surface-encapsulated niobium qubit devices exhibit T₁ relaxation times 2–5 times longer than baseline qubit devices with native niobium oxides. When capping niobium with tantalum, we obtain median qubit lifetimes above 300 μs, with maximum values up to 600 μs. Our comparative structural and chemical analysis provides insight into why amorphous niobium oxides may induce higher losses compared to other amorphous oxides.

Original language	English (US)
Article number	43
Journal	npj Quantum Information
Volume	10
Issue number	1
DOIs	https://doi.org/10.1038/s41534-024-00840-x
State	Published - Dec 2024

Funding

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 no. DE-AC02-07CH11359. This work made use of the Pritzker Nanofabrication Facility of the Institute for Molecular Engineering at the University of Chicago, which receives support from Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS-2025633), a node of the National Science Foundation\u2019s National Nanotechnology Coordinated Infrastructure. Ames National Laboratory is operated for the U.S. Department of Energy by Iowa State University under Contract No. DE-AC02-07CH11358. The authors thank members of the SQMS Center for valuable discussions.

ASJC Scopus subject areas

Computer Science (miscellaneous)
Statistical and Nonlinear Physics
Computer Networks and Communications
Computational Theory and Mathematics

Access to Document

10.1038/s41534-024-00840-x

Cite this

Bal, M., Murthy, A. A., Zhu, S., Crisa, F., You, X., Huang, Z., Roy, T., Lee, J., Zanten, D. V., Pilipenko, R., Nekrashevich, I., Lunin, A., Bafia, D., Krasnikova, Y., Kopas, C. J., Lachman, E. O., Miller, D., Mutus, J. Y., Reagor, M. J., ... Grassellino, A. (2024). Systematic improvements in transmon qubit coherence enabled by niobium surface encapsulation. npj Quantum Information, 10(1), Article 43. https://doi.org/10.1038/s41534-024-00840-x

@article{b91fd33575ec4fb0a97398ff0d302382,

title = "Systematic improvements in transmon qubit coherence enabled by niobium surface encapsulation",

abstract = "We present a transmon qubit fabrication technique that yields systematic improvements in T1 relaxation times. We encapsulate the surface of niobium and prevent the formation of its lossy surface oxide. By maintaining the same superconducting metal and only varying the surface, this comparative investigation examining different capping materials, such as tantalum, aluminum, titanium nitride, and gold, as well as substrates across different qubit foundries demonstrates the detrimental impact that niobium oxides have on coherence times of superconducting qubits, compared to native oxides of tantalum, aluminum or titanium nitride. Our surface-encapsulated niobium qubit devices exhibit T1 relaxation times 2–5 times longer than baseline qubit devices with native niobium oxides. When capping niobium with tantalum, we obtain median qubit lifetimes above 300 μs, with maximum values up to 600 μs. Our comparative structural and chemical analysis provides insight into why amorphous niobium oxides may induce higher losses compared to other amorphous oxides.",

author = "Mustafa Bal and Murthy, {Akshay A.} and Shaojiang Zhu and Francesco Crisa and Xinyuan You and Ziwen Huang and Tanay Roy and Jaeyel Lee and Zanten, {David van} and Roman Pilipenko and Ivan Nekrashevich and Andrei Lunin and Daniel Bafia and Yulia Krasnikova and Kopas, {Cameron J.} and Lachman, {Ella O.} and Duncan Miller and Mutus, {Josh Y.} and Reagor, {Matthew J.} and Hilal Cansizoglu and Jayss Marshall and Pappas, {David P.} and Kim Vu and Kameshwar Yadavalli and Oh, {Jin Su} and Lin Zhou and Kramer, {Matthew J.} and Florent Lecocq and Goronzy, {Dominic P.} and Torres-Castanedo, {Carlos G.} and Pritchard, {P. Graham} and Dravid, {Vinayak P.} and Rondinelli, {James M.} and Bedzyk, {Michael J.} and Hersam, {Mark C.} and John Zasadzinski and Jens Koch and Sauls, {James A.} and Alexander Romanenko and Anna Grassellino",

note = "Publisher Copyright: {\textcopyright} This is a U.S. Government work and not under copyright protection in the US; foreign copyright protection may apply 2024.",

year = "2024",

month = dec,

doi = "10.1038/s41534-024-00840-x",

language = "English (US)",

volume = "10",

journal = "npj Quantum Information",

issn = "2056-6387",

publisher = "Nature Partner Journals",

number = "1",

}

Bal, M, Murthy, AA, Zhu, S, Crisa, F, You, X, Huang, Z, Roy, T, Lee, J, Zanten, DV, Pilipenko, R, Nekrashevich, I, Lunin, A, Bafia, D, Krasnikova, Y, Kopas, CJ, Lachman, EO, Miller, D, Mutus, JY, Reagor, MJ, Cansizoglu, H, Marshall, J, Pappas, DP, Vu, K, Yadavalli, K, Oh, JS, Zhou, L, Kramer, MJ, Lecocq, F, Goronzy, DP, Torres-Castanedo, CG, Pritchard, PG, Dravid, VP , Rondinelli, JM , Bedzyk, MJ , Hersam, MC, Zasadzinski, J, Koch, J, Sauls, JA, Romanenko, A & Grassellino, A 2024, 'Systematic improvements in transmon qubit coherence enabled by niobium surface encapsulation', npj Quantum Information, vol. 10, no. 1, 43. https://doi.org/10.1038/s41534-024-00840-x

TY - JOUR

T1 - Systematic improvements in transmon qubit coherence enabled by niobium surface encapsulation

AU - Bal, Mustafa

AU - Murthy, Akshay A.

AU - Zhu, Shaojiang

AU - Crisa, Francesco

AU - You, Xinyuan

AU - Huang, Ziwen

AU - Roy, Tanay

AU - Lee, Jaeyel

AU - Zanten, David van

AU - Pilipenko, Roman

AU - Nekrashevich, Ivan

AU - Lunin, Andrei

AU - Bafia, Daniel

AU - Krasnikova, Yulia

AU - Kopas, Cameron J.

AU - Lachman, Ella O.

AU - Miller, Duncan

AU - Mutus, Josh Y.

AU - Reagor, Matthew J.

AU - Cansizoglu, Hilal

AU - Marshall, Jayss

AU - Pappas, David P.

AU - Vu, Kim

AU - Yadavalli, Kameshwar

AU - Oh, Jin Su

AU - Zhou, Lin

AU - Kramer, Matthew J.

AU - Lecocq, Florent

AU - Goronzy, Dominic P.

AU - Torres-Castanedo, Carlos G.

AU - Pritchard, P. Graham

AU - Dravid, Vinayak P.

AU - Rondinelli, James M.

AU - Bedzyk, Michael J.

AU - Hersam, Mark C.

AU - Zasadzinski, John

AU - Koch, Jens

AU - Sauls, James A.

AU - Romanenko, Alexander

AU - Grassellino, Anna

PY - 2024/12

Y1 - 2024/12

N2 - We present a transmon qubit fabrication technique that yields systematic improvements in T1 relaxation times. We encapsulate the surface of niobium and prevent the formation of its lossy surface oxide. By maintaining the same superconducting metal and only varying the surface, this comparative investigation examining different capping materials, such as tantalum, aluminum, titanium nitride, and gold, as well as substrates across different qubit foundries demonstrates the detrimental impact that niobium oxides have on coherence times of superconducting qubits, compared to native oxides of tantalum, aluminum or titanium nitride. Our surface-encapsulated niobium qubit devices exhibit T1 relaxation times 2–5 times longer than baseline qubit devices with native niobium oxides. When capping niobium with tantalum, we obtain median qubit lifetimes above 300 μs, with maximum values up to 600 μs. Our comparative structural and chemical analysis provides insight into why amorphous niobium oxides may induce higher losses compared to other amorphous oxides.

AB - We present a transmon qubit fabrication technique that yields systematic improvements in T1 relaxation times. We encapsulate the surface of niobium and prevent the formation of its lossy surface oxide. By maintaining the same superconducting metal and only varying the surface, this comparative investigation examining different capping materials, such as tantalum, aluminum, titanium nitride, and gold, as well as substrates across different qubit foundries demonstrates the detrimental impact that niobium oxides have on coherence times of superconducting qubits, compared to native oxides of tantalum, aluminum or titanium nitride. Our surface-encapsulated niobium qubit devices exhibit T1 relaxation times 2–5 times longer than baseline qubit devices with native niobium oxides. When capping niobium with tantalum, we obtain median qubit lifetimes above 300 μs, with maximum values up to 600 μs. Our comparative structural and chemical analysis provides insight into why amorphous niobium oxides may induce higher losses compared to other amorphous oxides.

UR - http://www.scopus.com/inward/record.url?scp=85191660863&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85191660863&partnerID=8YFLogxK

U2 - 10.1038/s41534-024-00840-x

DO - 10.1038/s41534-024-00840-x

M3 - Article

AN - SCOPUS:85191660863

SN - 2056-6387

VL - 10

JO - npj Quantum Information

JF - npj Quantum Information

IS - 1

M1 - 43

ER -

Systematic improvements in transmon qubit coherence enabled by niobium surface encapsulation

Abstract

Funding

ASJC Scopus subject areas

Access to Document

Other files and links

Fingerprint

Cite this