By a News Reporter-Staff News Editor at Science Letter -- Research findings on Quantum Dots are discussed in a new report. According to news reporting originating from Madison, Wisconsin, by NewsRx correspondents, research stated, "Several logical qubits and quantum gates have been proposed for semiconductor quantum dots controlled by voltages applied to top gates. The different schemes can be difficult to compare meaningfully."
Our news editors obtained a quote from the research from the University of Wisconsin, "Here we develop a theoretical framework to evaluate disparate qubit-gating schemes on an equal footing. We apply the procedure to two types of double-dot qubits: the singlet-triplet and the semiconducting quantum dot hybrid qubit. We investigate three quantum gates that flip the qubit state: a DC pulsed gate, an AC gate based on logical qubit resonance, and a gate-like process known as stimulated Raman adiabatic passage. These gates are all mediated by an exchange interaction that is controlled experimentally using the interdot tunnel coupling g and the detuning epsilon, which sets the energy difference between the dots. Our procedure has two steps. First, we optimize the gate fidelity (f) for fixed g as a function of the other control parameters; this yields an f (opt)(g) that is universal for different types of gates. Next, we identify physical constraints on the control parameters; this yields an upper bound f(max) that is specific to the qubit-gate combination. We show that similar gate fidelities (similar to 99.5%) should be attainable for singlet-triplet qubits in isotopically purified Si, and for hybrid qubits in natural Si."
According to the news editors, the research concluded: "Considerably lower fidelities are obtained for GaAs devices, due to the fluctuating magnetic fields Delta B produced by nuclear spins."
For more information on this research see: High-fidelity gates in quantum dot spin qubits. Proceedings of the National Academy of Sciences of the United States of America, 2013;110(49):19695-19700. Proceedings of the National Academy of Sciences of the United States of America can be contacted at: Natl Acad Sciences, 2101 Constitution Ave NW, Washington, DC 20418, USA. (National Academy of Sciences - www.nasonline.org/; Proceedings of the National Academy of Sciences of the United States of America - www.nasonline.org/publications/pnas/)
The news editors report that additional information may be obtained by contacting T.S. Koh, University of Wisconsin, Dept. of Phys, Madison, WI 53706, United States. Additional authors for this research include S.N. Coppersmith and M. Friesen (see also Quantum Dots).
Keywords for this news article include: Madison, Wisconsin, Quantum Dots, United States, Nanotechnology, Emerging Technologies, North and Central America
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