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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. |