Recently, weak measurements were used to measure small effects that are transverse to the propagation direction of a light beam. Here we address the question whether weak measurements are also useful for measuring small longitudinal phase shifts. We show that standard interferometry greatly outperforms weak measurements in a scenario involving a purely real weak value. However, we also present an interferometric scheme based on a purely imaginary weak value, combined with a frequency-domain analysis, which may have potential to outperform standard interferometry by several orders of magnitude.
@article{arxiv.0911.5139,
title = {Measuring small longitudinal phase shifts: weak measurements or standard interferometry?},
author = {Nicolas Brunner and Christoph Simon},
journal= {arXiv preprint arXiv:0911.5139},
year = {2010}
}