Researchers at the Niels Bohr Institute, University of Copenhagen, in collaboration with the French CEA-Leti, have found industrially-manufactured transistor wafers to be suitable as a qubit platform capable of moving to the second dimension, a significant step for a working quantum computer.
One of the key features of the devices is the two-dimensional array of quantum dots. Or more precisely, a two by two lattice of quantum dots.
Silicon quantum dots are attractive for the implementation of large spin-based quantum processors in part due to prospects of industrial foundry fabrication. However, the large effective mass associated with electrons in silicon traditionally limits single-electron operations to devices fabricated in customized academic clean rooms.
The team demonstrated single-electron occupations in all four quantum dots of a 2 x 2 split-gate silicon device fabricated entirely by 300-mm-wafer foundry processes. By applying gate-voltage pulses while performing high-frequency reflectometry off one gate electrode, they performed single-electron operations within the array that demonstrated single-shot detection of electron tunneling and an overall adjustability of tunneling times by a global top gate electrode.
They also used the two-dimensional aspect of the quantum dot array to exchange two electrons by spatial permutation, which may find applications in permutation-based quantum algorithms.
The result has been published in Nature Communications.