Article abstract
Nature Physics 3, 41 - 45 (2007)
doi:10.1038/nphys475
Subject Categories: Electronics, photonics and device physics | Condensed-matter physics | Quantum physics
Controllable valley splitting in silicon quantum devices
Srijit Goswami1,6, K. A. Slinker1,6, Mark Friesen1,6, L. M. McGuire1, J. L. Truitt1, Charles Tahan2, L. J. Klein1, J. O. Chu3, P. M. Mooney4, D. W. van der Weide5, Robert Joynt1, S. N. Coppersmith1 and Mark A. Eriksson1
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.
- Department of Physics, University of Wisconsin-Madison, Wisconsin 53706, USA
- Cavendish Laboratory, J J Thomson Avenue, Cambridge CB3 0HE, UK
- IBM Research Division, T. J. Watson Research Center, New York 10598, USA
- Department of Physics, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
- Department of Electrical and Computer Engineering, University of Wisconsin-Madison, Wisconsin 53706, USA
- These authors contributed equally to this work
Correspondence to: Mark Friesen1,6 e-mail: friesen@cae.wisc.edu
Correspondence to: Mark A. Eriksson1 e-mail: maeriksson@wisc.edu
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