On the robustness of holonomic quantum computation

Besides standard dynamical schemes to realize a quantum computer, there are particular approaches which are based on intrinsic properties of quantum systems, leading to the definition of topological computation and holonomic, or geometric, computation. The holonomic approach can be viewed as the application of non-Abelian geometric phases to quantum information processing, it is believed to be fault-tolerant with respect of certain kind of parametric noise. Here we discuss the issue of robustness of holonomic quantum gates under parametric noise: we distinguish between geometric and dynamical effects of cancelation, which can appear in different contexts. A so-called standard argument in favor of the stability of noisy holonomic quantum gates is reviewed and extended to more general settings. New geometric effects that describe the behavior of noisy holonomic gates are presented. These effects lead to a refining of the optimal strategy to achieve a robust computation.