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Events in Physics
Title: Fundamental Experiments With Entangled Photons: Status And Future Prospects    (Colloquia)
Start Date: 09/07/2010
Time: 5:00 pm
Location: 105 Stanley Hall
Speaker: Anton Zeilinger
Affiliation: Anton Zeilinger
Contact Person:   (510) 643-0572

The field of Quantum Information Science was essentially triggered by experiments in the foundations of quantum mechanics. The development of quantum information technology in return provides novel tools which also open up new possibilities for fundamental experiments. One example is the quantum link between the Canary Islands of Tenerife and La Palma which allows detailed tests of entanglement. Recently, an experiment there for the first time closed a loophole in Bell experiments related to Bell's requirement that the choice of measurement must be free and random, i.e. uninfluenced by the photon emission at the source. This is achieved by ensuring space-like separation of the decisions what will be measured from the emission event. In another series of experiments a number of nonlocal delayed choice and nonlocal quantum eraser experiments were performed using polarization entangled states. While Bell experiments test he possibility of a local realistic view, recent experiments testing theories proposed by Leggett provide evidence against an important class of nonlocal realistic theories. Another experiment tests the possibility of the existence of joint probability distributions for individual 2-state systems. The experiments rule out a class, not connected at all to the question of nonlocality. Future experimental possibilities include higher-dimensional Hilbert spaces. The fundamental physics in higher dimensional Hilbert spaces is largely unexplored terrain. It will certainly be interesting to investigate the formal structures of systems in Hilbert spaces of higher dimensions. It is to be expected that this will again open up new possibilities for quantum information science.