Fast evaluation of multielectron states for modeling of state preparation and measurement (SPAM) in quantum dot spin qubits

High fidelity SPAM in Si quantum dot spin qubits generally require large excited state splittings. Understanding the dependence of these states on bias voltages is therefore critical for optimizing qubit performance. In this talk, we show how to quickly model multi-electron eigenstates on a dense grid of bias voltages by treating voltage shifts as perturbations on a set of pre-computed configuration interaction (CI) eigenstates. We detail how this method can be used to compute highly accurate charge stability diagrams, capable of resolving relevant charge transition lines relevant for Pauli spin blockade (PSB). In addition, we show how these techniques can be used to optimize device operating bias configuration to enhance initialization times and readout fidelities. Our theory results show why it is favorable to initialize from the (2,0)-(3,0) charge transition compared to the (1,0)-(2,0) transition (as observed experimentally [1]), and provides bias trends for improving singlet-triplet energy splittings.



[1] J. Z. Blumoff et al., PRX Quantum 3, 010352 (2022)