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First demonstration of universal control of encoded spin qubits [phys.org]:

HRL Laboratories, LLC, has published the first demonstration of universal control of encoded spin qubits. This newly emerging approach to quantum computation uses a novel silicon-based qubit device architecture, fabricated in HRL's Malibu cleanroom, to trap single electrons in quantum dots. Spins of three such single electrons host energy-degenerate qubit states, which are controlled by nearest-neighbor contact interactions that partially swap spin states with those of their neighbors.

The encoded silicon/silicon germanium quantum dot qubits use three electron spins and a control scheme whereby voltages applied to metal gates partially swap the directions of those electron-spins without ever aligning them in any particular direction. The demonstration involved applying thousands of these precisely calibrated voltage pulses in strict relation to one another over the course of a few millionths of a second.

The quantum coherence offered by the isotopically enriched silicon used, the all-electrical and low-crosstalk-control of partial swap operations, and the configurable insensitivity of the encoding to certain error sources combine to offer a strong pathway toward scalable fault tolerance and computational advantage, major steps toward a commercial quantum computer.

"It is hard to define what the best qubit technology is, but I think the silicon exchange-only qubit is at least the best-balanced," said Thaddeus Ladd, HRL group leader and co-author.

Journal Reference: Aaron J. Weinstein et al, Universal logic with encoded spin qubits in silicon, Nature (2023). https://dx.doi.org/10.1038/s41586-023-05777-3 [doi.org]

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