An addressable quantum dot qubit with fault-tolerant control-fidelity

• Published in: Nature nanotechnology Vol. 9; no. 12; pp. 981 - 985
• Main Authors: Veldhorst, M., Hwang, J. C. C., Yang, C. H., Leenstra, A. W., de Ronde, B., Dehollain, J. P., Muhonen, J. T., Hudson, F. E., Itoh, K. M., Morello, A., Dzurak, A. S.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.12.2014; Nature Publishing Group
• Subjects: 142/126; 639/766/483/2802; 639/766/483/481; 639/925/357/1017; 639/925/927/481; Electrons; letter; Materials Science; Nanotechnology; Nanotechnology and Microengineering; Nitrogen; Quantum dots; Resonance; Silicon
• ISSN: 1748-3387; 1748-3395
• DOI: 10.1038/nnano.2014.216

A quantum bit that can be addressed with a gate voltage and has a very high control-fidelity can be realized in an electrically defined silicon quantum dot. Exciting progress towards spin-based quantum computing 1 , 2 has recently been made with qubits realized using nitrogen-vacancy centres in diamond and phosphorus atoms in silicon 3 . For example, long coherence times were made possible by the presence of spin-free isotopes of carbon 4 and silicon 5 . However, despite promising single-atom nanotechnologies 6 , there remain substantial challenges in coupling such qubits and addressing them individually. Conversely, lithographically defined quantum dots have an exchange coupling that can be precisely engineered 1 , but strong coupling to noise has severely limited their dephasing times and control fidelities. Here, we combine the best aspects of both spin qubit schemes and demonstrate a gate-addressable quantum dot qubit in isotopically engineered silicon with a control fidelity of 99.6%, obtained via Clifford-based randomized benchmarking and consistent with that required for fault-tolerant quantum computing 7 , 8 . This qubit has dephasing time T 2 * = 120 μs and coherence time T 2  = 28 ms, both orders of magnitude larger than in other types of semiconductor qubit. By gate-voltage-tuning the electron g *-factor we can Stark shift the electron spin resonance frequency by more than 3,000 times the 2.4 kHz electron spin resonance linewidth, providing a direct route to large-scale arrays of addressable high-fidelity qubits that are compatible with existing manufacturing technologies.