Dresden 2011 – scientific programme
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Q: Fachverband Quantenoptik und Photonik
Q 20: Quantum Information: Concepts and Methods 3
Q 20.1: Talk
Tuesday, March 15, 2011, 10:30–10:45, SCH A118
Experimental investigation of the uncertainty principle using entangled photons — •Robert Prevedel1, Deny Hamel1, Roger Colbeck2, Kent Fisher1, and Kevin Resch1 — 1Institute for Quantum Computing, University of Waterloo, Waterloo, N2L 3G1, ON, Canada — 2Perimeter Institute for Theoretical Physics, 31 Caroline Street North, Waterloo, Ontario N2L 2Y5, Canada
The uncertainty principle, first formulated by Heisenberg provides a fundamental limitation on an observer's ability to simultaneously predict the outcome when one of two measurements is performed on a quantum system. However, if the observer has access to a particle which is entangled with the system, his uncertainty is generally reduced: indeed, if the particle and system are maximally entangled, the observer can predict the outcome of both measurements precisely. This effect has recently been quantified by Berta et al. in a new, more general uncertainty relation. Here we perform experiments to probe the validity of this new inequality using entangled photon pairs. The behavior we find agrees with the predictions of quantum theory, satisfying the new uncertainty relation. An optical delay line that serves as a quantum memory, in combination with fast feed-forward allows an observer to gain more information and hence lower uncertainty about the outcome of an measurement than would be possible without the entanglement. This shows not only that the reduction in uncertainty caused by entanglement can be significant in practice, but also demonstrates the use of the inequality to witness entanglement.