Atomic fluctuations lifting the energy degeneracy in Si/SiGe quantum dots

Brian Paquelet Wuetz, Merritt P. Losert, Sebastian Koelling, Lucas E. A. Stehouwer, Anne-Marije J. Zwerver, Stephan G. J. Philips, Mateusz T. Mądzik, Xiao Xue, Guoji Zheng, Mario Lodari, Sergey V. Amitonov, Nodar Samkharadze, Amir Sammak, Lieven M. K. Vandersypen, Rajib Rahman, Susan N. Coppersmith, Oussama Moutanabbir, Mark Friesen and Giordano Scappucci ()
Additional contact information
Brian Paquelet Wuetz: Delft University of Technology
Merritt P. Losert: University of Wisconsin-Madison
Sebastian Koelling: École Polytechnique de Montréal
Lucas E. A. Stehouwer: Delft University of Technology
Anne-Marije J. Zwerver: Delft University of Technology
Stephan G. J. Philips: Delft University of Technology
Mateusz T. Mądzik: Delft University of Technology
Xiao Xue: Delft University of Technology
Guoji Zheng: Delft University of Technology
Mario Lodari: Delft University of Technology
Sergey V. Amitonov: Delft University of Technology
Nodar Samkharadze: QuTech and Netherlands Organisation for Applied Scientific Research (TNO)
Amir Sammak: QuTech and Netherlands Organisation for Applied Scientific Research (TNO)
Lieven M. K. Vandersypen: Delft University of Technology
Rajib Rahman: University of New South Wales
Susan N. Coppersmith: University of New South Wales
Oussama Moutanabbir: École Polytechnique de Montréal
Mark Friesen: University of Wisconsin-Madison
Giordano Scappucci: Delft University of Technology

Nature Communications, 2022, vol. 13, issue 1, 1-8

Abstract: Abstract Electron spins in Si/SiGe quantum wells suffer from nearly degenerate conduction band valleys, which compete with the spin degree of freedom in the formation of qubits. Despite attempts to enhance the valley energy splitting deterministically, by engineering a sharp interface, valley splitting fluctuations remain a serious problem for qubit uniformity, needed to scale up to large quantum processors. Here, we elucidate and statistically predict the valley splitting by the holistic integration of 3D atomic-level properties, theory and transport. We find that the concentration fluctuations of Si and Ge atoms within the 3D landscape of Si/SiGe interfaces can explain the observed large spread of valley splitting from measurements on many quantum dot devices. Against the prevailing belief, we propose to boost these random alloy composition fluctuations by incorporating Ge atoms in the Si quantum well to statistically enhance valley splitting.

Date: 2022
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DOI: 10.1038/s41467-022-35458-0

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