Simultaneous wave and particle knowledge in a neutron interferometer

City College of the City of New York, New York, NY 10031, USA
Physics Letters A (Impact Factor: 1.77). 01/1988; DOI: 10.1016/0375-9601(88)90114-4

ABSTRACT We give a measure of particle knowledge in a neutron interferometer that reflects one's ability to predict in which beam a neutron is located. We can measure wave knowledge by contrast of the interference pattern. Then one's simultaneous knowledge of both is determined by a single parameter (not an uncertainty relation), running from full particle to full wave knowledge. We extend the discussion to partially coherent beams. Our measure of information is much simpler than the conventional one.

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    ABSTRACT: The issue of interference and which-way information is addressed in the context of 3-slit interference experiments. A new inequality connecting the interference visibility and which-path distinguishability, ${\mathcal V} + {2{\mathcal D}\over 3- {\mathcal D}} \le 1$, is derived which puts a bound on how much fringe visibility and which-way information can be simultaneously obtained. The relation is different from the Englert-Greenberger-Yasin duality relation for the 2-slit experiments.
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    ABSTRACT: For a particle travelling through an interferometer, the trade-off between the available which-way information and the interference visibility provides a lucid manifestation of the quantum mechanical wave-particle duality. Here we analyse this relation for a particle possessing an internal degree of freedom such as spin. We quantify the trade-off with a general inequality that paints an unexpectedly intricate picture of wave-particle duality when internal states are involved. Strikingly, in some instances which-way information becomes erased by introducing classical uncertainty in the internal degree of freedom. Furthermore, even imperfect interference visibility measured for a suitable set of spin preparations can be sufficient to infer absence of which-way information. General results are illustrated with a proof-of-principle single-photon experiment.
    Nature Communications 10/2013; 4:2594. · 10.02 Impact Factor
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    ABSTRACT: Wave-particle duality of photons with losses in the Mach-Zehnder interferometer (MZI) is investigated experimentally and theoretically. The experiment is done with the standard MZI with the beam splitter or the beam merger being continuously varied. The losses are deliberately introduced either inside the MZI (the two arms between the beam splitter and beam mergers) or outside the MZI (after the beam merger). It is proved that the unbalanced losses have great influence on the predictability P (particle nature) and visibility V (wave nature). For the former case the duality inequality holds while for the later the duality inequality is "violated". We get P^2 + V^2 > 1. This "violation" can be eliminated by witching the two paths and detectors then averaging the results. The observed results can be exactly explained theoretically.