78 research outputs found
Modified Two-Slit Experiments and Complementarity
Some modified two-slit interference experiments claim to demonstrate a
violation of Bohr's complementarity principle. A typical such experiment is
theoretically analyzed using wave-packet dynamics. The flaw in the analysis of
such experiments is pointed out and it is demonstrated that they do not violate
complementarity. In addition, it is quite generally proved that if the state of
a particle is such that the modulus square of the wave-function yields an
interference pattern, then it necessarily loses which-path information.Comment: Revised version, to appear in J. Quantum Inf. Sc
Popper's Experiment: A Modern Perspective
Karl Popper had proposed an experiment to test the standard interpretation of
quantum mechanics. The proposal survived for many year in the midst of no clear
consensus on what results it would yield. The experiment was realized by Kim
and Shih in 1999, and the apparently surprising result led to lot of debate. We
review Popper's proposal and its realization in the light of current era when
entanglement has been well studied, both theoretically and experimentally. We
show that the "ghost-diffraction" experiment, carried out in a different
context, conclusively resolves the controversy surrounding Popper's experiment.Comment: Review article (11 pages, 2-column) published versio
Popper's experiment, Copenhagen Interpretation and Nonlocality
A thought experiment, proposed by Karl Popper, which has been experimentally
realized recently, is critically examined. A basic flaw in Popper's argument
which has also been prevailing in subsequent debates, is pointed out. It is
shown that Popper's experiment can be understood easily within the Copenhagen
interpretation of quantum mechanics. An alternate experiment, based on discrete
variables, is proposed, which constitutes Popper's test in a clearer way. It
refutes the argument of absence of nonlocality in quantum mechanics.Comment: Thoroughly revised. To appear in Int. J. Quantum Informatio
Ghost Interference and Quantum Erasure
The two-photon ghost interference experiment, generalized to the case of
massive particles, is theoretically analyzed. It is argued that the experiment
is intimately connected to a double-slit interference experiment where, the
which-path information exists. The reason for not observing first order
interference behind the double-slit, is clarified.It is shown that the
underlying mechanism for the appearance of ghost interference is, the more
familiar, quantum erasure.Comment: Published versio
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