Experimental realization of Popper's experiment - Violation of the uncertainty principle?

Uncertainty, being perhaps the most basic principle of quantum mechanics, d istinguishes the world of quantum phenomena from the realm of classical phy sics. Quantum entanglement, being perhaps the most surprising consequence o f quantum mechanics, on the other hand apparently suggests paradoxes relati ng to or violations of the quantum mechanical uncertainty principle in some experimental situations. Popper's thought experiment is an example. We wis h to report a recent realization of Popper's experiment. The experimental d ata show that there appears to be a violation of the uncertainty principle. This is, however as we shall argue in this paper, only an illusion provide d that we take the teachings of quantum mechanics seriously.