Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Microscopy and Microanalysis

Identifying Possible Two-Level-System Sources in Superconducting Qubit with Advanced Electron Microscopy

Lin Zhou, Jin‐Su Oh, Xiaotian Fang, Tae‐Hoon Kim, Matt J. Kramer, Alexander Romanenko, Sam Posen, Anna Grassellino, Cameron Kopas, Mark Field, Jayss Marshall, J. Mutus, Hilal Cansizoglu, Matthew J. Reagor

Published Jul 22, 2022• 0 citations
Publisher

Abstract

Lin Zhou, Jin-Su Oh, Xiaotian Fang, Tae-Hoon Kim, Matt Kramer, A Romanenko, S Posen, A Grassellino, Cameron J Kopas, Mark Field, Jayss Marshall, Joshua Y M
DOI
10.1017/s1431927622006808

Related papers

Probing Sources of Decoherence at Defects and Interfaces in Superconducting Quantum Materials and Devices

Akshay A. Murthy, Roberto dos Reis, Stephanie M. Ribet +4 more

Akshay A Murthy, Roberto dos Reis, Stephanie M Ribet, Mattia Checchin, Anna Grassellino, Vinayak P Dravid, Alexander Romanenko; Probing Sources of Decohere

Microscopy and Microanalysis•Jul 22, 2022•0 citations

The Unique Role of Electron Microscopy in Unraveling and Mitigating Materials Sources of Decoherence in Superconducting Quantum Devices

Peter G Lim, G. Santos, Roberto dos Reis +4 more

Microscopy and Microanalysis•Jul 1, 2025•1 citation

Material and Interface Engineering Strategies to Mitigate Decoherence in Superconducting Qubits

Dominic P. Goronzy, Anthony McFadden, David A. Garcia Wetten +16 more

While significant strides have been made to increase the coherence time of superconducting qubits, further advancements are essential for realizing scalable quantum computing. Decoherence is often a result of loss and noise stemming from two-level systems and excess quasiparticles, arising due to material defects, fabrication processes, and ambient exposure, particularly at surfaces and interfaces. Our recent efforts to mitigate these decoherence mechanisms have employed a variety of strategies, including low-loss surface encapsulation materials, advanced substrate preparation techniques, modifications to metal film growth, and the development of novel fabrication processes. The structural and chemical properties of materials, surfaces, and interfaces are studied using scanning probe microscopy, electron microscopy, photoelectron spectroscopy, mass spectrometry, and X-ray diffraction, which is correlated to device performance metrics, including superconducting resonator internal quality factor and qubit T1 time. This information is used to identify and understand material sources of loss and their origins in the device fabrication process. Through multi-institution efforts within SQMS we have identified the loss mechanism of interstitial hydrogen in niobium-based devices and shown how standard fabrication processes introduce these hydrides, developing strategies to mitigate their formation.1 Furthermore, we have characterized the metal-substrate interface, including the loss of niobium-silicides formed at that interface, and developed silicon surface treatments that reduce atomic scale roughness and oxygen content at the metal-substrate and Josephson junction interfaces.2-4 By developing the connection between materials properties and the overall performance of superconducting quantum circuitry, we can develop fabrication strategies to mitigate material losses, thus supporting the ongoing efforts to enhance coherence time in superconducting quantum devices. 1. Torres-Castanedo, C. G.*, Goronzy, D. P.*, et al., Adv. Funct. Mater., 2401365 (2024) 2. Lu, X., et al., Phys. Rev. Materials 6, 064402 (2022) 3. Berti, G., Appl. Phys. Lett. 122, 192605 (2023) 4. Kopas, C. J., Goronzy, D. P., et al., arXiv:2408.02863 (2024)

•Sep 23, 2024•0 citations

Electron-Two-Level System Interaction and Superconductivity

G. M. Vujčić

De Gruyter eBooks•Dec 31, 1984•0 citations

Candidate TLS Defects at the Al-Si Interface in a Superconducting Qubit from STEM-based Structure Refinement

Soohyun Im, Venkata Surya Chaitanya Kolluru, Keith G. Ray +6 more

Two-level systems (TLSs) are the dominant source of decoherence in superconducting qubits, a leading platform for quantum computing. While TLSs are believed to arise from atomic-scale tunneling defects, their precise structural origins, particularly at complex and disordered interfaces in real devices, have remained elusive. Conventional structural characterization is extremely challenging because these interfaces are non-periodic, containing steps and roughness, and device-relevant TLS defects involve only atomic motions with small energy differences. We have determined the atomic character of candidate TLSs at the Al-Si interface of a superconducting qubit using aberration-corrected scanning transmission electron microscopy (STEM) combined with experiment-constrained 3D structure modeling and computational defect searching. High-angle annular dark-field (HAADF) STEM images were obtained from a disordered interface containing a prominent step defect and localized strain. Structure modeling started with 3D models created in the Ingrained framework to match the experimental projections, accounting for mistilt and uniform strain. These models were then refined using FANTASTX (Fully Automated Nanoscale To Atomistic Structure from Theory and eXperiments), a multi-objective optimizer that simultaneously minimizes disagreement with the experimental image via structural similarity and the ab initio (DFT) total system energy. Transition-state searches with the activation relaxation technique nouveau (ARTn) on the refined models identified many atomic configurations occupying double-well potentials corresponding to TLS. Statistical analysis of over 1500 TLSs shows that candidate TLS with tunneling energies and asymmetries in the range relevant to superconducting qubits (∼5 GHz) predominantly involve Al atoms located near the interface. These atoms exhibit smaller median tunneling displacements (∼0.44 Å) than the non-candidate TLS and reside in locally disordered environments with marginally longer and less dense first-neighbor shells than those of non-candidate TLSs. The most probable candidate TLSs feature cooperative motion of one or two Al atoms, and sometimes with Si, in directions largely parallel to the interface. This work provides the first direct atomic-scale insight into the structural defects that may be responsible for decoherence at a realistic, device-relevant interface. It also demonstrates a scalable, generalizable workflow for solving the atomic structure of complex, disordered interfaces by integrating aberration-corrected STEM with advanced computational refinement and defect searching. The methodology is directly applicable to other materials systems and heterointerfaces critical to quantum devices [5].

Microscopy and Microanalysis•Jul 1, 2026•0 citations

Advances in Quantum Electronics, Volume 3

Arthur Maitland

Optica Acta International Journal of Optics•Jun 1, 1976•0 citations
While significant strides have been made to increase the coherence time of superconducting qubits, further advancements are essential for realizing scalable quantum computing. Decoherence is often a result of loss and noise stemming from two-level systems and excess quasiparticles, arising due to material defects, fabrication processes, and ambient exposure, particularly at surfaces and interfaces. Our recent efforts to mitigate these decoherence mechanisms have employed a variety of strategies, including low-loss surface encapsulation materials, advanced substrate preparation techniques, modifications to metal film growth, and the development of novel fabrication processes. The structural and chemical properties of materials, surfaces, and interfaces are studied using scanning probe microscopy, electron microscopy, photoelectron spectroscopy, mass spectrometry, and X-ray diffraction, which is correlated to device performance metrics, including superconducting resonator internal quality factor and qubit T1 time. This information is used to identify and understand material sources of loss and their origins in the device fabrication process. Through multi-institution efforts within SQMS we have identified the loss mechanism of interstitial hydrogen in niobium-based devices and shown how standard fabrication processes introduce these hydrides, developing strategies to mitigate their formation.1 Furthermore, we have characterized the metal-substrate interface, including the loss of niobium-silicides formed at that interface, and developed silicon surface treatments that reduce atomic scale roughness and oxygen content at the metal-substrate and Josephson junction interfaces.2-4 By developing the connection between materials properties and the overall performance of superconducting quantum circuitry, we can develop fabrication strategies to mitigate material losses, thus supporting the ongoing efforts to enhance coherence time in superconducting quantum devices. 1. Torres-Castanedo, C. G.*, Goronzy, D. P.*, et al., Adv. Funct. Mater., 2401365 (2024) 2. Lu, X., et al., Phys. Rev. Materials 6, 064402 (2022) 3. Berti, G., Appl. Phys. Lett. 122, 192605 (2023) 4. Kopas, C. J., Goronzy, D. P., et al., arXiv:2408.02863 (2024)
Two-level systems (TLSs) are the dominant source of decoherence in superconducting qubits, a leading platform for quantum computing. While TLSs are believed to arise from atomic-scale tunneling defects, their precise structural origins, particularly at complex and disordered interfaces in real devices, have remained elusive. Conventional structural characterization is extremely challenging because these interfaces are non-periodic, containing steps and roughness, and device-relevant TLS defects involve only atomic motions with small energy differences. We have determined the atomic character of candidate TLSs at the Al-Si interface of a superconducting qubit using aberration-corrected scanning transmission electron microscopy (STEM) combined with experiment-constrained 3D structure modeling and computational defect searching. High-angle annular dark-field (HAADF) STEM images were obtained from a disordered interface containing a prominent step defect and localized strain. Structure modeling started with 3D models created in the Ingrained framework to match the experimental projections, accounting for mistilt and uniform strain. These models were then refined using FANTASTX (Fully Automated Nanoscale To Atomistic Structure from Theory and eXperiments), a multi-objective optimizer that simultaneously minimizes disagreement with the experimental image via structural similarity and the ab initio (DFT) total system energy. Transition-state searches with the activation relaxation technique nouveau (ARTn) on the refined models identified many atomic configurations occupying double-well potentials corresponding to TLS. Statistical analysis of over 1500 TLSs shows that candidate TLS with tunneling energies and asymmetries in the range relevant to superconducting qubits (∼5 GHz) predominantly involve Al atoms located near the interface. These atoms exhibit smaller median tunneling displacements (∼0.44 Å) than the non-candidate TLS and reside in locally disordered environments with marginally longer and less dense first-neighbor shells than those of non-candidate TLSs. The most probable candidate TLSs feature cooperative motion of one or two Al atoms, and sometimes with Si, in directions largely parallel to the interface. This work provides the first direct atomic-scale insight into the structural defects that may be responsible for decoherence at a realistic, device-relevant interface. It also demonstrates a scalable, generalizable workflow for solving the atomic structure of complex, disordered interfaces by integrating aberration-corrected STEM with advanced computational refinement and defect searching. The methodology is directly applicable to other materials systems and heterointerfaces critical to quantum devices [5].