We study the corrections to adiabatic dynamics of two coupled quantum dot spin-qubits, each dot singly occupied with an electron, in the context of a quantum computing operation. Tunneling causes double occupancy at the conclusion of an operation and constitutes a processing error. We model the gate operation with an effective two-level system, where non-adiabatic transitions correspond to double occupancy. The model is integrable and possesses three independent parameters. We confirm the accuracy of Dykhne's formula, a nonperturbative estimate of transitions, and discuss physically intuitive conditions for its validity. Our semiclassical results are in excellent agreement with numerical simulations of the exact time evolution. A similar approach applies to two-level systems in different contexts.
@article{arxiv.cond-mat/0409096,
title = {Double Occupancy Errors in Quantum Computing Operations: Corrections to Adiabaticity},
author = {Ryan Requist and John Schliemann and Alexander G. Abanov and Daniel Loss},
journal= {arXiv preprint arXiv:cond-mat/0409096},
year = {2007}
}