cjh@petsd.UUCP (Chris Henrich) (10/10/84)
[]
Here is a suggestion for "resolving" the "paradox" of the
Aspect experiment:
The experimenters create a situation in which two
particles are widely separated, but a correlation exists
between their states. As a result, when one particle is
observed, something appears to travel from the site of that
observation to the other one.
This appearance vanishes, if we say that the
correlation between the two particles exists in both places
where the particles are. I think this is a usable way of
speaking. After all, the correlation is a physical reality,
since its presence can be tested. If its location does not
consist of both places, what is its location?
Note that the idea of a bilocated entity is implicit in
the formalism of wave mechanics for a two-particle system.
The Schroedinger wave function of this system determines a
probability distribution over the set of *pairs* of possible
locations for the component parts.
I am not really happy with my own suggestion; I think it
does not get at the heart of any terribly important matter.
That is why I put quote-marks around the words 'paradox' and
'resolving.' I can't be sure that I have resolved a paradox,
because I can't seem to convince myself that a paradox has
been pointed out. After all, somebody remarked that the
mysterious action at a distance can be emulated by putting a
marble in one of two boxes and separating the boxes.
There is something very odd about the metaphysical
foundations of quantum mechanics. I am reminded of the
experience of waking up with a headache: while still mostly
asleep, I was dimly aware of a discomfort, though quite unable
to categorize it. The paradox of quantum mechanics is just as
elusive as the location of my headache.
Regards,
Chris
--
Full-Name: Christopher J. Henrich
UUCP: ..!(cornell | ariel | ukc | houxz)!vax135!petsd!cjh
US Mail: MS 313; Perkin-Elmer; 106 Apple St; Tinton Falls, NJ 07724
Phone: (201) 870-5853tjr@ihnet.UUCP (Tom Roberts) (10/10/84)
The EPR "paradox" in QM is not really a paradox, but merely a way of pointing out that you must be VERY CAREFUL when interpreting experiments involving quantum-mechanical systems. Consider instead the QM system consisting of a single 2-sided coin (heads and tails) after a random coin toss. In order to learn which side is up, you must perform a measurement upon the system (i.e. look at the coin). Assuming a typical coin (i.e. VERY large on the atomic scale), it is no surprise that a single measurement of the system is sufficient to determine its state. You merely look at the top face of the coin; in particular, YOU DO NOT NEED TO LOOK AT THE BOTTOM OF THE COIN, TOO. The EPR gedanken-experiment is merely a different kind of coin-toss. If you wish to determine whether a single particle confined in a box is in one half or the other, it IS sufficient to measure only one half to determine the answer (assuming negligible probability for the particle to change sides after or because of the measurement). The "paradox" arises when you don't keep in mind that you must take account of the ENTIRE system: the left-half of the box, the right-half of the box, and the particle. When you ask "why does a measurement in this half of the box affect the situation in that half of the box (far away) ?" you are NOT thinking of the entire system, but are (erroneously) considering two separated, non-interacting subsystems (the two sides of the box). It isn't clear in which subsystem the particle is in, AND THAT IS THE POINT. In this mode of thinking, you have NOT made a proper separation of the system into non-interacting subsystems. Tom Roberts ihnp4!ihnet!tjr
hull@hao.UUCP (Howard Hull) (10/13/84)
[] I agree with C.J. Henrich. Even something so simple as the theory of special relativity implies that if a photon is emitted at the beginning of the big bang, and somehow manages to escape absorbtion until the "end" of the universe, it knows no time. For its own sake, it is absorbed at the same moment as it is emitted, and even in what might be described as an "adjacent" place. The Lorentz contraction is complete; ahead, it sees (as a surface) only the point where it will be absorbed. Behind, it sees only the point (again as a surface) from which it was emitted. Orthogonal to its path, a direction to which it is not coupled, it "sees" the entire remaining universe in some why that does not betray the passage of time therein. If someone in that universe places a "dark slide" in the path of the photon "after" it is emitted, the photon already knows that it will be absorbed at the dark slide. If the dark slide was not in place "in time", the photon knows that, too. Einstein was right: God does not play dice with the Universe. HE knows the outcome of these things; it is we that play the dice, for we know not the outcome. If two photons are emitted together, each knows at one instant from whence it has come and to whence it shall go. By this means, a causal connection is made instantly through the three space-time points. (Are these causal connections Saffarti's "Fibers"?) It is only we that occupy perhaps just one of the three sites that find it convenient to say that the events are unknonwn and as yet (to our notion of time) unconnected; That is why Henrich can say: > This appearance vanishes, if we say that the > correlation between the two particles exists in both places > where the particles are. The space-time location where both particles "are" is defined in their frame of refrence, not ours. Henrich notes that the authority of the photon frame of reference carries through in the transfer of energy and momentum defined by the emission and the absorbtion: > since its presence can be tested. If its location does not > consist of both places, what is its location? What has one location in one reference system, but two locations in another? Easy: an "event" that has no temporal separation in one system (i.e. it is "properly temporal" in that system) but does show temporal separation in another. This does imply some relative motion between the two refrence frames, but we seldom are careful enough to analyze for this. > Note that the idea of a bilocated entity is implicit in > the formalism of wave mechanics for a two-particle system. Gotta be. I'm beginning to feel very warm now; perhaps an intense radiation field approaches :-) Photon Flames (assuming you know where they came from as well as when they left and where they're going and when they'll get there) to: {ihnp4!stcvax | decvax!stcvax | seismo} !hao!hull