Qubits talk at a distance

Marcus Stephen Edwards

Kai‐Mei C. Fu

G Kandasamy, Cameron J. Wellard, Lloyd C. L. Hollenberg

We theoretically investigate cross-talk in hyperfine gate control of donor-qubit quantum computer architectures, in particular the Kane proposal. By solving the Poisson and Schrödinger equations numerically for the gated donor system, we calculate the change in hyperfine coupling and thus the error in spin-rotation for the donor nuclear-electron spin system, as the gate-donor distance is varied. We thus determine the effect of cross-talk-the inadvertent effect on non-target neighbouring qubits-which occurs due to closeness of the control gates (20-30 nm). The use of compensation protocols is investigated, whereby the extent of cross-talk is limited by the application of compensation bias to a series of gates. In the light of these factors, architectural implications are then considered.

Bob Coecke, Giovanni de Felice, Konstantinos Meichanetzidis +1 more

Giorgio Nicolí, Michael S. Ferguson, Clemens Rössler +7 more

Scalable architectures for quantum information technologies require one to selectively couple long-distance qubits while suppressing environmental noise and cross talk. In semiconductor materials, the coherent coupling of a single spin on a quantum dot to a cavity hosting fermionic modes offers a new solution to this technological challenge. Here, we demonstrate coherent coupling between two spatially separated quantum dots using an electronic cavity design that takes advantage of whispering-gallery modes in a two-dimensional electron gas. The cavity-mediated, long-distance coupling effectively minimizes undesirable direct cross talk between the dots and defines a scalable architecture for all-electronic semiconductor-based quantum information processing.

Almut Beige, Berthold‐Georg Englert, Christian Kurtsiefer +1 more