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Quantum information processing with semiconductor technology: from qubits to integrated quantum circuits

M. Veldhorst
QuTech and Kavli Institute of Nanoscience, Delft University of Technology, The Netherlands

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Our approach toward scalable quantum technology departs from the transistor, the most replicated structure made by mankind. We define qubits on the spin states of electrons and holes in silicon and germanium quantum dots. In this talk, I will present our recent results in increasing the qubit quality and quantity. First, we show that even a single hole can be coherently controlled. By exploiting the strong spin-orbit interaction of holes we obtain fast qubit operation with gate fidelities of 99.99%, setting new benchmarks for quantum dot systems. Furthermore, through dynamical decoupling, we obtain record coherence times for holes and by applying this technique as a band filter we are able to measure the transversal hyperfine interaction with nuclear spins. Second, we demonstrate that quantum dot qubits and control electronics can be operated in the same temperature regime. In addition, we show that qubits can be realized using a fully industrial 300 mm wafer process. These together define a key step toward integrated quantum circuits. Third, we construct a 2x2 quantum dot array and show qubit coupling in two dimensions. We obtain universal control and demonstrate coherent execution of a quantum circuit that entangles and disentangles all four qubits. Finally, I will present our strategies to overcome qubit-to-qubit variations, aiming to build quantum systems with fewer control lines than a number of qubits, targeting to achieve a quantum advantage with the same materials and techniques that enabled today's information age.


Menno Veldhorst is group leader at QuTech, the lead of the QuTech Academy, and portfolio director at the extension school of the TU Delft. Veldhorst received his PhD cum laude at the University of Twente (in the groups of prof. A. Brinkman and prof. H. Hilgenkamp). He performed his postdoctoral research at the University of New South Wales in the group of prof. A. Dzurak, where he demonstrated single and two-qubit logic in silicon, mentioned as one of the top ten breakthroughs in physics in 2015 by Physics  World. His group at QuTech introduced planar germanium qubits, demonstrated universal logic with silicon above one Kelvin, and realized four-qubit logic with quantum dots. He has published more than 60 papers, including 18 publications in the Science and Nature journals. For his contributions to silicon and germanium quantum technology, he received the Nicholas Kurti Science Prize and he is listed as a visionary in the MIT Technology Review list of 35 innovators under 35. As lead QuTech Academy, Veldhorst develops massive online courses (MOOCs) on quantum technology, which have attracted already over 80.000 students.