In the 1987 spin retrodiction puzzle of Vaidman, Aharonov, and Albert one is challenged to ascertain the values of σx, σy, and σz of a spin-1/2 particle by utilizing entanglement. We report the experimental realization of a quantum-optical version in which the outcome of an intermediate polarization projection is inferred by exploiting single-photon two-qubit quantum gates. The experimental success probability is consistently above the 90.2% threshold of the optimal one-qubit strategy, with an average success probability of 95.6%.
@article{arxiv.quant-ph/0209127,
title = {Ascertaining the Values of $\sigma_x$, $\sigma_y$, and $\sigma_z$ of a Polarization Qubit},
author = {Oliver Schulz and Ruprecht Steinhübl and Markus Weber and Berthold-Georg Englert and Christian Kurtsiefer and Harald Weinfurter},
journal= {arXiv preprint arXiv:quant-ph/0209127},
year = {2009}
}
Comments
4 pages, 2 figures; final version with new title and new abstract; to appear in Physical Review Letters