Um apagador quântico com estados de Bell

Abstract

In this dissertation, an optical quantum eraser experiment, which can be considered an optical analogy of an experiment proposed by Scully, Englert and Walther(SEW) [1] is performed. Using photons in entangled Bell-states, we can choose whether to observe which-path information or an interference pattern. An appealing feature of this quantum eraser is that the experiement actually uses a Young double-slit to create interference. One photon of an entangled pair is incident on a Youngdouble slit of appropriate dimensions to create an interference pattern on a distant \screen". Quarter-wave plates, orientated so that their fast axes are orthogonal, are placed in front of each slit, serve as which-path markers. The presence of the quarter-wave plates destroys the interference pattern. To recover interference, an appropriate polarization measurement on the other entangled photon is performed. In addition, a \delayed quantum erasure" experiment is performed. The dangers of an erroneous interpretation of quantum theory in the delayed erasure situation are briey discussed. The generation of polarization-entangled photons using spontaneous parametric down-conversion is briey studied. It is shown that, through type-II non-colinear phase matching, the non-linear BBO (_-BaB2O4) cristal creates highly-entangled photons. Curves of polarization interference are obtained, proportional to sin(_A _ _B), with visibilities greater than 0:95.