We demonstrate phase super-resolution in the absence of entangled states. The key insight is to use the inherent time-reversal symmetry of quantum mechanics: our theory shows that it is possible to \emph{measure}, as opposed to prepare, entangled states. Our approach is robust, requiring only photons that exhibit classical interference: we experimentally demonstrate high-visibility phase super-resolution with three, four, and six photons using a standard laser and photon counters. Our six-photon experiment demonstrates the best phase super-resolution yet reported with high visibility and resolution.
@article{arxiv.quant-ph/0511214,
title = {Time-reversal and super-resolving phase measurements},
author = {K. J. Resch and K. L. Pregnell and R. Prevedel and A. Gilchrist and G. J. Pryde and J. L. O'Brien and A. G. White},
journal= {arXiv preprint arXiv:quant-ph/0511214},
year = {2008}
}