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Coffee House => Coffee House Boards => CH / Science and Technology => Topic started by: orange on January 22, 2008, 12:15:17 PM

Title: teleportation
Post by: orange on January 22, 2008, 12:15:17 PM

Interesting slashdot story (http://science.slashdot.org/science/08/01/18/2259219.shtml)

one of comments says:

Quote

A pair of photons in the same state, on the other hand, are indistinguishable.

how can we be sure of that? maybe there is some property that is not the same, well at least their position heh..

Title: Re: teleportation
Post by: Wain on January 23, 2008, 09:50:45 AM

While I suppose that could be distinctly possible, in the end it would be some property we do not yet understand how to observe, which in turn makes the comment about the two photons being indistinguishable still correct.  

Appeal to ignorance is a logical fallacy.

Title: Re: teleportation
Post by: Cymric on January 23, 2008, 03:29:32 PM

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how can we be sure of that?

Because we are. Photons are integer spin particles called 'bosons', and all bosons share this particular property of being indistinguishable. If this were not the case, lasers would not exist as we know them. Look up the heading of photon in Wikipedia for further information.

Title: Re: teleportation
Post by: orange on January 24, 2008, 08:21:58 AM

aha, it also says here: http://en.wikipedia.org/wiki/Bell%27s_Theorem

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The standard assumption in Quantum Optics is that "all photons of given frequency, direction and polarization are identical"

I was wrong.

Title: Re: teleportation
Post by: Trev on January 24, 2008, 08:46:21 AM

I'm no physicist, but doesn't the uncertainty principle sort of rule out ever knowing whether two particles are identical?

In any case, don't let the rules kill your imagination. Supposition is as good a place to start as any.

Title: Re: teleportation
Post by: Wain on February 10, 2008, 03:30:47 AM

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I'm no physicist, but doesn't the uncertainty principle sort of rule out ever knowing whether two particles are identical?

If they had the same location and momentum wouldn't there only be one particle?  I don't think the uncertainty principle is going to get in the way here.  

I would assume that location is not considered to have to be the same for two distinct particles in order to consider them "identical", just everything else (spin, energy level, momentum, etc...).
 

Title: Re: teleportation
Post by: orange on February 12, 2008, 12:31:47 PM

hm, if they are in different locations, then electrical/magnetic/gravity field in their coordinates (of ALL other particles in universe) is probably different, so doesn't that affect their state? (so that it is different too)