Re: News Story about split photons

First of all, I want to apologize for taking so long to answer your question. I could not find anything about a news story regarding a split photon being sent down a fiber, with a 'Y' at each end. I did not give up there though! ;-) After discussions with several people and numerous searches on the web, I learned a lot about this phenomena I think you are speaking of and found a recent experiment that is very similar (maybe the same?). I hope this will answer your question.

The following article from the New York Times explains explains the basic experiment (keep in mind that the jounalist's views of the phenomena are just one side of a very controversial topic):

QUANTUM PHOTON ENTANGLEMENT AT A DISTANCE OF SEVEN MILES
Whether or not the quantum mechanical behavior of elementary
particles is called mysterious depends, more or less, on the
attitude one has. If there is a demand that the behavior of these
particles be explainable with the logistic structure of human
language, then some aspects of their behavior seem mysterious
indeed. On the other hand, if there is a willingness to admit
that the logical structure of human language may not at present
be isomorphic with the logical structure of the laws that govern
the behavior of these particles, then it is probably best to put
off notions of mysteries and take the behavior for what it is.
This week there was announced to the popular press, before
publication, the results of a twin-photon experiment in
Switzerland. Nicolas Gisin et al (University of Geneva, CH)
reported that a pair of twin photons split and sent along two
diverging paths, when arriving at terminals seven miles apart,
exhibit the phenomenon of quantum "entanglement". The gist of it
is that the detection of one of the photons effectively causes
the collapse of the spectrum of its wave-function solutions to a
single solution, and this collapse instantaneously causes the
collapse of the possible quantum states of the other photon, in
this case seven miles away. The melodramatic notion (purveyed by
the press) is that information has somehow travelled from one
photon to the other at a speed greater than the speed of light,
with the result that great canons of thought are thereby
destroyed. But perhaps the more prosaic reality is that any
attempt to describe non-classical events with language based on
classical laws and perceptions cannot succeed. 
(New York Times 22 July)

One possible expanation of what is happening can be found by looking at the Quantum Mechanical, Heisenberg Uncertainty Principle. The Heisenberg Uncertainty Principle states that "it is impossible to prepare states in which members of certain pairs of variables, called 'compementary variables', have values determined with arbitrary precision. If one of the variables of a complimentary pair is measured, information is inevitably lost about the other". (Bransden, 1994) This appears to be what is happening, as when one of the photons is detected, the wavefunction of the other one collapses.

Now, there are opposing views on this subject. One side (like I mentioned in the last paragraph) says that the measurement of one photon is indeed affecting the other - often called "action at a distance" or a non-local effect. The other side says that the one photon may 'appear' to affect the other, but this is merely an artifact of (or artifical error in) the measurement.

If the the supporters of "action at a distance" are right, then this is truly a great day for science! As mentioned in the above article, this would mean that the photons send information between each other instantly (faster than the speed of light) - just think of what this could do for the communications industry! ;-)

In conclusion, nobody 'really' knows what the real answer to what is happening here......although lots of people will probably tell you they do! A lot more work will have to be done before conclusive proof will be obtained and 'most' people are satified with what is really going on. If you want to read more on this phenomena, get yourself a good book, magazine, website, etc., on quantum mechanics and look up Bell's Theorem and the EPR Paradox (Einstein-Podolsky-Rosen). I did not get into these principles in this answer, because they can be complex and I did not want to confuse either of us! (My quantum text's 'attempt' at an explaination is mainly just equations.) Below, I also listed some websites to check out.

I hope my explaination helped you. If you have any further questions, please feel free to email me.

Kurt Frost kfrost@sympatico.ca

WEBSITES:

Bell's Theorem - a paper discussing Bell's Theorem

Apeiron Publication Information - a site that has many papers discussing topics related to this issue and other areas of modern physics

REFERENCES:

Bransden, B.H., and C.J. Joachain. 1994. Introduction to Quantum Mechanics. Essex (England): Longman Scientific & Technical.