We also discuss the application of cascade-based spin readout to densely-packed two-dimensional quantum dot arrays with charge sensors placed at the periphery. We implement and analyse several operating modes for cascades and analyse their scaling behaviour. We demonstrate that a cascade of electrons can be combined with Pauli spin blockade to read out distant spins and show results with potential for high fidelity using a remote charge sensor in a quadruple quantum dot device. A cascade can transmit information along a quantum dot array over a distance that extends by far the effect of the direct Coulomb repulsion. Here we show that the Coulomb repulsion allows an initial charge transition to induce subsequent charge transitions, inducing a cascade of electron hops, like toppling dominoes. The electron charge in turn allows control of the position of individual electrons in a quantum dot array, and enables charge sensors to probe the charge configuration.

The spin of a single electron in a semiconductor quantum dot provides a well-controlled and long-lived qubit implementation.

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