Controlling quantum dot level spacing: moving beyond the constant interaction model

Proposed large scale implementation of gate defined semiconductor quantum dots requires effective means to tune each dot to desired tunnel coupling, capacitive coupling to gates, and coupling to sources of decoherence such as the phonon bath. These parameters are currently understood within the context of the constant interaction model that predicts a periodic level spacing based on a constant capacitance of each dot to the relevant gates. Yet, the actual capacitance of the dot is not a constant and depends on parameters including the electron number, voltage of the associated gates, and size of the dot, leading to a nonlinear level spacing. We show how taking these parameters into consideration enables greater control of each quantum dot. We also present a means to change the dot level spacing, thereby changing the coupling to the phonon bath, while maintaining desired tunnel coupling in a framework similar to virtual gating for cross capacitance. The results are relevant to minimizing decoherence in quantum dot qubits.