On Tuesday, December 4, 2012 1:51:55 PM UTC-5, Brent wrote:
> On 12/4/2012 8:29 AM, John Clark wrote:
> > wrote:
>> > That's where you're wrong; read the paper more carefully. If you
>> record the which-way the interference is lost. [...] The interference
>> pattern occurs *only* if the which way information is *erased*
> Nope, you've got it exactly precisely backwards yet again. I quote from
> " If the experimenters know which slit it goes through, the photon will
> behave as a particle. If they do not know which slit it goes through, the
> photon will behave as if it were a wave when it is given an opportunity to
> interfere with itself. "
> That's why you need to read the technical papers instead of Wikipedia.
> The above is correct when there are just photons going through one pair of
> slits. But in the Delayed Quantum Eraser experiment there are *two*
> entangled photons one of which goes through slits and one of which *could
> be detected and give which-way information*. The point is that if it is
> not detected (flys off to infinity, absorbed in the wall,...) the
> interference pattern is still destroyed. To maintain the pattern the
> information in the entangled photon has to be *erased* - that's the
> function of the lens.
> Loss of the interference isn't because "they do not know"; it's a
> consequence of the information being "out there" - and being absorbed in a
> wall still leaves it "out there". This is even clearer in the buckyball
> Young's slits experiment, quant-ph/0402146v1. The interference pattern is
> lost when the buckyballs are hot enough that their IR radiation is
> sufficient to localize them to the slit spacing - even though nobody ever
> observes or detects the IR photons.
> All those below fail to consider the relevant case too; they assume all
> cases in which no experimenter measures which-way are equivalent. They
> ignore the possibility that "the environment" may measure which-way but no
> person does.
It's confusing. Can you simplify it?
One photon heads toward the slits.
One entangled photon heads toward the detector. (They are both entangled
with each other, but I assume you mean one pair of entangled photons, not
Is there a detector on the slits too?
It seems like the point of the experiment is that the interference pattern
only shows up when the ability to discern which-way is not available -
which seems to me to support observer-principle type interpretations.
Certainly I don't see any suggestion that there is a such thing as
'information' which is independent of some kind of sense receptivity. To
Time 6. Upon accessing the information gathered by the Coincidence Circuit,
> we the observer are shocked to learn that the pattern shown by the
> positions registered at D0 at Time 2 *depends entirely* on the
> information *gathered* later at Time 4 and available to us at the
> conclusion of the experiment.
> The position of a photon at detector D0 has been registered and scanned.
> Yet the actual position of the photon arriving at D0 *will be at one
> place if we later learn* more information; and the actual position will
> be at another place if we do
I intentionally bolded the terms where the true nature of quantum is
revealed - with the capacity to detect, 'learn', 'gather', i.e. to become
informed through a sensory-motor event within the matter which makes up a
physical instrument (including, but not limited to, human eyes, brains,
Physics is sensory-motor participation. Nothing more and nothing less.
There is no such thing as 'information'.
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