Re: Why do we observe double slit interference?

From: scerir (scerir_at_libero.it)
Date: 09/15/04

  • Next message: Urs Schreiber: "Re: Two notions of 2-multiplication" 
    Date: Wed, 15 Sep 2004 12:11:31 +0000 (UTC)

    "Oz"
    > I don't (any longer) believe in photons as existing in a beam of light.
    > I think its just a maxwellian field (ok with spin), the quantum
    > behaviour arises because all detectors are quantised (typically
    > requiring jumping an energy gap). So there never is any question of
    > 'which slit did the photon go through' because as a field, it can
    > and will go through both. That said this isn't actually very much
    > help because all emitters and all detectors are quantised, you never
    > see light in any other way.

    All detectors are quantized. And N.Bohr said: "The hypothesis of
    light-quanta is not able to throw light on the nature of radiation."
    (in the 1922 Nobel Lecture, at that time Bohr was 'conservative'!).
    But how to explain that *just* one detector 'clicks' and the other
    don't? See, J.J.Thorn et al., Am.J.Phys., 72, p.1210, 2004.
                              [Abstract]
    While the classical, wavelike behavior of light (interference
    and diffraction) has been easily observed in undergraduate
    laboratories for many years, explicit observation of the quantum
    nature of light (i.e., photons) is much more difficult.
    For example, while well-known phenomena such as the photoelectric
    effect, and Compton scattering, strongly suggest the existence of
    photons, they are not *definitive* proof of their existence.
    [Leonard Mandel wrote the same, so: no doubt about it!]
    Here we present an experiment, suitable for an undergraduate
    laboratory, that unequivocally demonstrates the quantum nature of light.
    Spontaneously downconverted light is incident on a *beamsplitter* and
    the outputs are monitored with single-photon counting detectors
    [2 detectors].
    We observe a near absence of *coincidence* counts between the two
    detectors - a result inconsistent with a classical wave model of light,
    but consistent with a quantum [particle] description in which individual
    photons are incident on the beamsplitter. More explicitly, we measured
    the degree of second-order coherence between the outputs to be
                           g(2)(0) = 0.0177±0.0026
    which violates the classical inequality
                           g(2)(0)>=1
    by 377 standard deviations.
                                [End of Abstract]

    s.

  • Next message: Urs Schreiber: "Re: Two notions of 2-multiplication"

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