We show that some composite pulses widely employed in NMR experiments are regarded as non-adiabatic geometric quantum gates with Aharanov-Anandan phases. Thus, we reveal the presence of a fundamental issue on quantum mechanics behind the traditional technique of the composite pulses. To examine the robustness of such composite pulses against fluctuations, we present a practical noise model in a two-level system. Then, we find that the composite pulses possesses purely geometrical nature even under a specific type of fluctuations.
@article{arxiv.0903.2295,
title = {Composite pulses in NMR as non-adiabatic geometric quantum gates},
author = {Yukihiro Ota and Yasusi Kondo},
journal= {arXiv preprint arXiv:0903.2295},
year = {2009}
}