Re: New look for classic double-slit quantum-interference experiment
From: Mark Fergerson (nunya_at_biz.ness)
Date: 03/09/05
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Date: Tue, 08 Mar 2005 19:01:47 -0700
mmeron@cars3.uchicago.edu wrote:
> In article <4flXd.21419$FM3.10069@fed1read02>, Mark Fergerson <nunya@biz.ness> writes:
>
>>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/
>>
>> where you'll find a "chatty" explanation of the experiment. He says
>>there about the intensity of the fields:
>>
>> "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 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.
>>
>> 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.
>>
>> <I keep waiting for Mati or somebody to whack me upside the head for my
>> miscomprehension, but nothing so far. Maybe he's stopped reading me.>
>>
> Nah. My "to read" list is rather short nowadays, but you're certainly
> on it. Not much time to write, though, we've a run period coming.
Thanks Mati; nice to know there's a steadying hand out there ready to
put me back on track.
<BTW, can you say what you're about to run?>
> Anyway, I didn't read the detailed description yet (see "time
> shortage", above) but this is a real neat experiment. And as for
> pulling out an electron, well, atomic fields (in the outer electron
> region are of the order 0f 0.1-1 TV/m, so the field generated by the
> laser is way more than adequate for the job.
Thought so. I hope you do get to read the whole thing; what we're
stuck on is whether or not the two positive peaks act as the slits. It
seems obvious to me, but Quantum Mirror apparently thinks that's just
too weird to be right; specifically, he said above that:
> each peak would need to produce half of the electron
I see no problem with that concept any more than with the standard
two-slit experiment. It's just mundane Quantum Weirdness turned
sideways. Whaddya think?
Mark L. Fergerson
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