Controllable valley splitting in silicon quantum devices
Author: ["Srijit Goswami","K. A. Slinker","Mark Friesen","L. M. McGuire","J. L. Truitt","Charles Tahan","L. J. Klein","J. O. Chu","P. M. Mooney","D. W. van der Weide","Robert Joynt","S. N. Coppersmith","Mark A. Eriksson"]
Publication: Nature Physics
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Abstract
Silicon has many attractive properties for quantum computing, and the quantum-dot architecture is appealing because of its controllability and scalability. However, the multiple valleys in the silicon conduction band are potentially a serious source of decoherence for spin-based quantum-dot qubits. Only when a large energy splits these valleys do we obtain well-defined and long-lived spin states appropriate for quantum computing. Here, we show that the small valley splittings observed in previous experiments on Si–SiGe heterostructures result from atomic steps at the quantum-well interface. Lateral confinement in a quantum point contact limits the electron wavefunctions to several steps, and enhances the valley splitting substantially, up to 1.5 meV. The combination of electrostatic and magnetic confinement produces a valley splitting larger than the spin splitting, which is controllable over a wide range. These results improve the outlook for realizing spin qubits with long coherence times in silicon-based devices.
Cite this article
Goswami, S., Slinker, K., Friesen, M. et al. Controllable valley splitting in silicon quantum devices. Nature Phys 3, 41–45 (2007). https://doi.org/10.1038/nphys475
