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From: ronse@prlb2.UUCP (Christian Ronse)
Newsgroups: sci.physics,sci.philosophy.tech
Subject: Re: a QM paradox (??)
Message-ID: <335@prlb2.UUCP>
Date: Wed, 5-Aug-87 04:39:28 EDT
Article-I.D.: prlb2.335
Posted: Wed Aug  5 04:39:28 1987
Date-Received: Fri, 7-Aug-87 07:00:46 EDT
References: <3794@oberon.USC.EDU>
Distribution: world
Organization: Philips Research Laboratory, Brussels
Lines: 51
Keywords: Uncertainity Principle
Summary: This is like EPR
Xref: mnetor sci.physics:1969 sci.philosophy.tech:359

In article <3794@oberon.USC.EDU>, mathur@pollux.usc.edu (Samir Kumar Mathur) 
writes:
} Here is a thought experiment which seems to violate Uncertainity Principle (UP)
} that came up at a casual discussion with a friend.
} 
} Scenario : 
} 	There are two particles A and B and I am trying to measure their
} 	momentum and positions accurately.
} 
} Experiment :
} 	(1) At time t:
} 		(a) I measure the momentums p(A,t) & p(B,t) and hence
} 			p(A&B,t) = p(A,t) + p(B,t) as accurately as I wish.
} 
} 	(2) At time t+dt:
} 		(a) I measure the momentum of A, p(A,t+dt) as accurately
} 			as I wish.
} 		(b) I measure the position of B, q(B,t+dt) as accurately
} 			as I wish.
} 		(c) I calculate p(B,t+dt) = p(A&B,t) - p(A,t+dt) 
} 			{conservation of momentum} as accurately as I wish.
} 
} Conclusion:
} 	From steps 2(b),(c) I conclude that I can measure p(B,t+dt),q(B,t+dt)  
} 	as accurately as I wish. This obviously violates Heisenberg's UP.
 
This is very close to the original statement of the Einstein-Podolsky-Rosen
paradox. They assume two particles A and B having interacted at time t. Then
their respective position and momentum are related. At time t one measures the
position of A and the momentum of B, which allows one to deduce the position
of B and the momentum of A, and so violate the uncertainty principle.

This has been tested in various experiments with the X, Y, and Z components of
spin instead of position and momentum, especially in the Aspect experiment.

That topic has been discussed at length in sci.physics a few months ago.


--------------------
Christian Ronse		maldoror@prlb2.UUCP
{seismo|philabs|mcvax|...}!prlb2!{maldoror|ronse}

``So goodnight, kids, and remember...everybody has a pointer in their
  heart, set to that special someone...don't keep yours set to nil...''

		        		Basil Hosmer
		        		Kaptain Kloodge Saga

-- 
Christian Ronse		maldoror@prlb2.UUCP
{seismo|philabs|mcvax|...}!prlb2!{maldoror|ronse}