A quantum dot structure having a split-gate geometry is provided. The quantum dot is configured for incorporation into a quantum dot array of a quantum processing unit. A gap between a reservoir accumulation gate and a quantum dot accumulation gate provides a tunnel barrier between an electric charge reservoir and a quantum dot well. An electrical potential applied to the gates defines a tunnel barrier height, width and charge tunneling rate between the well and the reservoir without relying on any barrier gate to control the charge tunneling rate.