We have made the first experimental demonstration of the simultaneous minimum uncertainty product between two complementary observables for a two-state system (a qubit). A partially entangled two-photon state was used to perform such measurements. Each of the photons carries (partial) information of the initial state thus leaving a room for measurements of two complementary observables on every member in an ensemble.
@article{arxiv.quant-ph/0012124,
title = {Simultaneous minimum-uncertainty measurement of discrete-valued complementary observables},
author = {Alexei Trifonov and Gunnar Bjork and Jonas Soderholm},
journal= {arXiv preprint arXiv:quant-ph/0012124},
year = {2007}
}