Qubits made from semiconductor quantum dots are a potential platform for future quantum computing. Although quantum gates with high fidelity have been demonstrated, the coupling of such qubits over distances, for example for use in quantum registers, remains a challenge. Mills et al. now show how they can controllably shuttle single electrons through a linear array of quantum dots.
The researchers define nine Si quantum dots in a Si/SiGe heterostructure by an advanced gate structure. They use three charge sensors to map out the nine-dimensional charge stability space. The adjustment of the chemical potentials of the dots and the connecting tunnelling barrier enables the controlled transfer of a single electron between neighbouring dots.
Furthermore, the transition from a control scheme based on physical gate voltages to a virtual gate scheme strongly diminishes the effect of crosstalk between quantum dots and allows the researchers to control several electrons within the array independently.
Mills et al. then design a control sequence that shuttles a single electron through the array in either direction within about 50 ns. With more complex sequences, two or three electrons can move through the array at a time, well separated by at least one empty dot at all times.
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