Practical strategies for enhancing the valley splitting in Si/SiGe quantum wells
Merrit P. Losert (University of Wisconsin-Madison)
M. A. Eriksson (University of Wisconsin-Madison)
Robert Joynt (University of Wisconsin-Madison)
Rajib Rahman (University of New South Wales)
G. Scappucci (TU Delft - QCD/Scappucci Lab, Kavli institute of nanoscience Delft, TU Delft - QuTech Advanced Research Centre)
Susan N. Coppersmith (University of New South Wales)
Mark Friesen (University of Wisconsin-Madison)
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Abstract
Silicon/silicon-germanium heterostructures have many important advantages for hosting spin qubits. However, controlling the valley splitting (the energy splitting between the two low-lying conduction-band valleys) remains a critical challenge for ensuring qubit reliability. Broad distributions of valley splittings are commonplace, even among quantum dots formed on the same chip. In this work, we theoretically explore the interplay between quantum-well imperfections that suppress the valley splitting and cause variability, such as broadened interfaces and atomic steps at the interface, while self-consistently accounting for germanium concentration fluctuations. We consider both conventional and unconventional approaches for controlling the valley splitting and present concrete strategies for implementing them. Our results provide a clear path for achieving qubit uniformity in a scalable silicon quantum computer.