Orthogonal control of tunnel couplings and cascade-based readout in a quantum dot array*

Electrostatically-defined semiconductor quantum dot (QD) arrays offer a promising platform for quantum computation and quantum simulation. However, crosstalk of gate voltages to inter-dot tunnel couplings, and a limited sensitivity range of a charge sensor based on Coulomb repulsion, pose challenges for the control and readout of large-scale QD arrays. Here, we show two new techniques to overcome these issues. First, we present that the crosstalk on tunnel couplings can be efficiently characterized and compensated for, since the same exponential dependence applies to all gates. We demonstrate efficient calibration of crosstalk in a quadruple QD array and define a set of virtual barrier gates, with which we show orthogonal control of all inter-dot tunnel couplings. Next, we report on cascade-based remote, fast, and high-fidelity spin readout. The Coulomb repulsion allows an initial charge transition to induce subsequent charge transitions, inducing a cascade of electron hops. Combining the electron cascade with Pauli spin blockade, we demonstrate fast and high-fidelity readout of distant spins using a remote charge sensor in the QD array. Our work marks a key step forward in the control and readout of large-scale QD arrays.