Terahertz near-field imaging of sidewall-induced losses in superconducting qubits
Correlating superconducting qubit performance with advanced materials analysis is a key strategy for improving coherence. Existing diagnostics for key properties, such as dielectric loss, structural discontinuity, and interface heterogeneity, often rely on destructive electron microscopy or low-throughput millikelvin measurements. Here, we demonstrate noninvasive terahertz (THz) nano-imaging/spectroscopy of encapsulated niobium transmon qubits as a high-throughput proxy for performance evaluation. We identify large variations in sidewall near-field signals, implicating sidewall loss and discontinuity as major coherence limiters, and also use THz hyperspectral line scans to probe dielectric responses and field participation at Al junction interfaces.
Authors
- Thomas Koschny (ORCID: https://orcid.org/0000-0003-4960-9266)
- R. K. Chan (ORCID: https://orcid.org/0009-0009-6368-8918)
- Anna Grassellino (ORCID: https://orcid.org/0000-0002-3985-8296)
- Shaojiang Zhu (ORCID: https://orcid.org/0000-0002-9318-0092)
- Alexander Romanenko (ORCID: https://orcid.org/0000-0003-1378-0870)
- Francesco Crisa (ORCID: https://orcid.org/0000-0003-3536-4528)
- J.-M. Park (ORCID: https://orcid.org/0000-0001-9936-7512)
- Akshay A. Murthy (ORCID: https://orcid.org/0000-0001-7677-6866)
- D. Olaya (ORCID: https://orcid.org/0000-0001-6901-3457)
- M. J. Kramer (ORCID: https://orcid.org/0000-0002-9097-6730)
- P. F. Hopkins (ORCID: https://orcid.org/0000-0003-4353-0901)
- Lin Zhou (ORCID: https://orcid.org/0000-0003-2286-6510)
- Jin‐Su Oh (ORCID: https://orcid.org/0000-0002-7462-3142)
- Andrei Lunin (ORCID: https://orcid.org/0000-0002-9009-6792)
- Samuel Haeuser (ORCID: https://orcid.org/0000-0003-4262-5538)
- Richard H. J. Kim (ORCID: https://orcid.org/0000-0002-4244-9653)
- Jigang Wang (ORCID: https://orcid.org/0000-0002-6159-4119)
- Mustafa Bal (ORCID: https://orcid.org/0000-0003-0751-6774)
- Sabrina Garattoni
Institutions
- Fermi National Accelerator Laboratory (US)
- National Institute of Standards and Technology (US)
- Iowa State University (US)
- Ames National Laboratory (US)
Publication Details
- Journal
- Applied Physics Letters
- Published
- 2025-09-15
- DOI
- https://doi.org/10.1063/5.0284028
- Primary Topic
- Near-Field Optical Microscopy
- Type
- article
- Field-Weighted Citation Impact
- 0.00