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Silicon Encoded Spin Qubits Achieve Universality

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Render of a six-dot SLEDGE device in silicon, which implemented universal logic with encoded spin qubits.

Said HRL scientist Aaron Weinstein, "Significant effort was placed in developing efficient, automated routines for determining what applied voltage led to what degree of partial swap."

Credit: HRL Laboratories

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.

Posted online ahead of publication in the journal Nature, the HRL experiment demonstrated universal control of their encoded qubits, which means the qubits can be used successfully for any kind of quantum computational algorithm implementation. 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 article is entitled Universal logic with encoded spin qubits in silicon.

From HRL Laboratories
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