%0 Journal Article
%T Experimental investigation of the uncertainty principle in the presence of quantum memory and its application to witnessing entanglement
%A Prevedel, Robert
%A Hamel, Deny R.
%A Colbeck, Roger
%A Fisher, Kent
%A Resch, Kevin J.
%J Nature Physics
%D 2011
%V 7
%N 10
%F Prevedel_etal2011
%O exported from refbase (https://db.rplab.ru/refbase/show.php?record=821), last updated on Sat, 12 May 2012 14:56:44 -0500
%X Heisenberg's uncertainty principle provides a fundamental limitation on the ability of an observer holding classical information to predict the outcome when one of two measurements is performed on a quantum system. However, an observer with access to a particle (stored in a quantum memory) which is entangled with the system generally has a reduced uncertainty: indeed, if the particle and system are maximally entangled, the observer can perfectly predict the outcome of whichever measurement is chosen. This effect has recently been quantified in a new entropic uncertainty relation. Here we experimentally investigate this relation, showing its effectiveness as an efficient entanglement witness. We use entangled photon pairs, an optical delay line serving as a simple quantum memory and fast, active feed-forward. Our results quantitatively agree with the new uncertainty relation. Our technique acts as a witness for almost all entangled states in our experiment as we obtain lower uncertainties than would be possible without the entangled particle.
%K fromIPMRAS
%P 757-761