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arXiv · 2112.09606

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·Giordano Scappucci
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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.

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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, Giordano Scappucci. 2022-12-01. Atomic fluctuations lifting the energy degeneracy in Si/SiGe quantum dots. https://doi.org/10.1038/s41467-022-35458-0

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