Kavli Affiliate: Giordano Scappucci
| First 5 Authors: Brian Paquelet Wuetz, Merritt P. Losert, Sebastian Koelling, Lucas E. A. Stehouwer, Anne-Marije J. Zwerver
| Summary:
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, predict, and control 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 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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