Fidelity of optimally controlled quantum gates with randomly coupled multiparticle environments

TL;DR

This paper demonstrates that optimal control techniques can achieve high-fidelity quantum gates in complex environments, showing robustness to environmental randomness and minimal impact from environmental interactions.

Contribution

It reveals that environmental interactions have negligible effects on gate fidelity and that optimal control is highly robust against random environmental coupling variations.

Findings

Environmental interactions minimally affect gate fidelity.

Optimal control achieves high-fidelity gates despite environmental randomness.

Gates are robust to variations in coupling strengths.

Abstract

This work studies the feasibility of optimal control of high-fidelity quantum gates in a model of interacting two-level particles. One particle (the qubit) serves as the quantum information processor, whose evolution is controlled by a time-dependent external field. The other particles are not directly controlled and serve as an effective environment, coupling to which is the source of decoherence. The control objective is to generate target one-qubit gates in the presence of strong environmentally-induced decoherence and under physically motivated restrictions on the control field. It is found that interactions among the environmental particles have a negligible effect on the gate fidelity and require no additional adjustment of the control field. Another interesting result is that optimally controlled quantum gates are remarkably robust to random variations in qubit-environment and inter-environment coupling strengths. These findings demonstrate the utility of optimal control for management of quantum-information systems in a very precise and specific manner, especially when the dynamics complexity is exacerbated by inherently uncertain environmental coupling.