Research Meeting

• Wonhee Ko (University of Tennessee, Knoxville)

Room: 233 Ride from hotel to IAMM

Materials-driven design of superconducting quantum devices

• Patrick Strohbeen (MIT)

Room: 310 Superconducting quantum devices have undergone a massive renaissance since the first demonstration of the Cooper pair box in 1999 [1]. Utilizing the same general material structure (Al/AlOx/Al), much of the dramatic improvement over the past few decades is a direct result of better device engineering and design. However, studies and proposals challenging the standard materials paradigm of superconducting devices have become increasingly popular in recent years as a route towards improving the coherence of such devices. One of the more mature efforts has been to introduce alternative superconducting metals for the base metallization layer, namely Ta [2], replacing the more common Al and Nb metals used in modern devices. Yet, the continued reliance on the Al/AlOx/Al Josephson junction (JJ) remains a pain point, largely due to the lossy amorphous AlOx material and sensitivity of Al to aggressive chemical cleaning procedures. Here, I will discuss some of the efforts I have pursued during my postdoctoral studies at New York University (NYU) in developing new materials for superconducting qubits to overcome long-standing issues that plague this technology. To this end, I developed a process of growing superconducting germanium thin films as a path towards epitaxial JJ structures integrated with group IV substrates [3]. A comprehensive structural, chemical, and electronic study of this material demonstrates the emergence of superconductivity in germanium through heavy substitutional doping of Ga metal. This system offers a unique approach towards epitaxial JJs utilizing doped semiconductors that readily interface with their un-doped phase that enables wafer-scale tri-layer qubit fabrication utilizing pristine crystalline materials. I will conclude with a brief discussion on my work at the Massachusetts Institute of Technology further pursuing the development of materials in superconducting quantum computing technology. [1]: Y. Nakamura, Y. A. Pashkin, and J. S. Tsai, Nature, 398, 786-788 (1999). [2]: M. P. Bland and F. Bahrami et al., Nature, 647, 343-348 (2025). [3]: J. A. Steele and P. J. Strohbeen et al., Nat. Nanotechnol., 20, 1757-1763 (2025).

Research Meeting

• Joon Sue Lee (University of Tennessee, Knoxville)

Room: 254

Research Meeting

• Ruixing Zhang (Department of Physics and Astronomy, University of Tennessee Knoxville)

Room: 323

Research Meeting Room: 303

Research Meeting

• Yishu Wang (University of Tennessee Knoxville)

Room: 312

Research Meeting

• Hanno Weitering

Research meeting

• Wonhee Ko (University of Tennessee, Knoxville)

Room: G028 Lab tour