Re: New look for classic double-slit quantum-interference experiment

From: Quantum Mirror (junebug_at_pgrb.com)
Date: 03/08/05 

Date: 8 Mar 2005 12:38:10 -0800

Mark Fergerson wrote:
> Quantum Mirror wrote:
> >> It's worse. Did you read the next-to-the-last paragraph? Note that

> >> there're two "positive" peaks in the laser pulses, but only one
> >> "negative" pulse. The negative pulses kick electrons out the other
> >> way and produce no interference pattern because there's no energy
> >> difference to create one. So in a sense, you simultaneously get
> >> complete and no "which-way" information about each electron that
> >> did produce the pattern
> >
> > They are saying that the two peaks act as the two slits. I can
find
> > no preprint or paper describing the exact experiment. This is a
> > strange idea to me.
>
> Yup, neither can I, and me too.
>
> > The time must be so short it is much smaller than the wavelength of
> > the light. For this to act like a slit in the fashion they are
> > describing each peak would need to produce half of the electron.
>
> It's basically just photoionization, but with previously
unachievable,
> nearly unbelievable control.
>
> The article includes a link to Paulus' webpage:
>
> http://faculty.physics.tamu.edu/ggp/
> "The pulses can be focussed down to a spot size with a diameter
> comparable to the wavelength thus causing intensities of the order of
> 10^20 W/cm^2. Such intensities are associated with tremendous field
> strengths. The electric part would have an amplitude of 20 TV/m..."
>
> Seems reasonable that such field strength should be adequate to
yank
> an electron loose even on one peak.
>
> He says about the duration of the peaks:
>
> "Such pulses consist (full-width half-maximum) of less than two
> optical cycles only (few-cycle pulses). This means that the pulse
> envelope changes almost as fast as the field oscillates. Therefore,
the
> temporal evolution of the field depends on the phase of the carrier
wave
> with respect to the envelope."
>
> This is the "nearly unbelievable" part; that adequate field
strength
> to free an electron can be turned on and off at a chosen location, in
a
> preferred direction, pretty much at will.
>
> > Are they saying that because we can't know which peak created the
> > electron complementarity or uncertainty plays a part in the
> > interference?
>
> Apparently so. From the article:
>
> "The team registered the arrival times of the electrons at both
> detectors and then plotted the number of electrons as a function of
> energy. The researchers observed interference fringes at the first
> detector because it was impossible to know if an electron counted by
the
> detector was produced during the first or second maximum."
>
> > Someone has misunderstood the details of this and I would like to
see
> > the paper.
>
> I'm not sure why you say that, and so would I.

I say that because I don't believe complementarity can act as a slit!!
I am not a big fan of voodoo physics.
>
> > I think a alternative explanation for this would be the two peaks
> > produce two electrons which interfere with each other.
>
> If two electrons were produced it would be obvious from the
ionization
> state of the remnant atoms (determinable from the recombination glow
> color, return current from the electron detectors etc). That isn't
> mentioned.

>>From a PDF on Paulus's web site:

Figure 2 shows Ar++ ion momentum (Pk) distributions
along the laser polarization direction for different CE
phases measured at a fixed laser pulse width (5 fs) and
intensity (350 TW=cm2). The ion momentum resolution
is 0.1 a.u. The spectra reflect the distributions of the
corresponding sum-momentum component of the two photoelectrons

> If the experiment proves to show what they think it does, it puts
a
> neat twist in the old quantum computing game. As I mentioned, we now
> simultaneously have total and zero "which-way" information about the
> interfering particles depending on which way you look at it, because
> this is basically the standard Young's Experiment "done sideways" so
to
> speak.

What he said was:
"We have complete which-way information and no which-way information
at the same time for the same electron,"

One electron?

I have found the paper that is a precursor to this one and the science
editor at Phisicsweb has it wrong.

http://faculty.physics.tamu.edu/ggp/Publications/041-PaulusAbsPhTheoryPhysScript04.pdf
 If you read on page 123 (excerpt from Phisica Scripta not that many
pages in this PDF) 4th paragraph on the right column, the explanation
is completely logical. No cut and paste from the document or I would
have.

Relevant Pages

  • Re: New look for classic double-slit quantum-interference experiment
    ... >> They are saying that the two peaks act as the two slits. ... >> describing each peak would need to produce half of the electron. ... The researchers observed interference fringes at the first ... return current from the electron detectors etc). ...
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  • Re: New look for classic double-slit quantum-interference experiment
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