From: paul@mtnmath.UUCP (Paul Budnik)
Newsgroups: sci.physics
Subject: Re: Hidden variable theories, was: Uncertainty Princi
Date: 13 Sep 92 03:50:14 GMT
Organization: Mountain Math Software, P. O. Box 2124, Saratoga. CA 95070

In article <1992Sep11.151800.14271@oracorp.com>, daryl@oracorp.com (Daryl McCullough) writes:
> I don't think that Shannon's theory of information can be used to
> support your claim that quantum mechanics involves instantaneous
> transmission of information across large distances.
> 
> In order for there to be a transmission of information, there must be
> a sender and a receiver of the information. Information is transmitted
> to the extent that there is a correlation between the choices made by
> the sender and the results observed by the receiver.

I do not see how choices are involved. Weather satellites transmit large
quantities of information about the atmosphere and oceans to ground stations.
Nobody chooses what that information is. The only choices are where the
camera is pointed and what parameters it is set at.

> There is no such
> correlation in quantum mechanics. No matter what choice is made by the
> sender in an EPR-like experiment, the probability distribution on
> possible results for the receiver is unchanged.

But the results at the receiver are changed in an experimentally detectable
way. The probability distribution for each detection is unchanged. The
probability distribution for joint detections at both sites is changed.
This tells us something about what is happening at the distant site.
One can measure the quantity of information that needed to be transferred
to produce the correlations for a stream of a given length.

> The case with encryption is a false analogy. When a message is
> encrypted, there is still a perfect correlation between messages sent
> and messages received, so by Shannon, the information transmission
> rate is the same as if the messages were unencrypted (actually
> slightly less, since encrypted messages generally have more redundancy
> than the unencrypted messages, depending on the encryption algorithm).
> Encrypted messages *can* (and are) used to communicate.

They can only be used to communicate if the receiver has the the
decryption key. You can send a message with EPR
correlations and you can decrypt the message. The only thing you cannot
do is decrypt it *immediately* after it is sent. I agree that this is not
a perfect analogy, but it demonstrates how information can be sent without
sending a signal. This is what happens if the encryption method is
a perfect one time pad and the receiver does not have access to the
decryption key. In that case even the NSA cannot decrypt it.

The critical point is that a distant manipulation changes what happens at a
local site in an experimentally detectable way. The process of detecting
that a physical event occurs is the detection of information about that
event. Some of the information used for this purpose must be transmitted
by standard methods. Bell's result and quantum mechanics implys that some
of it was transferred instantaneously when remote manipulations influenced
local detections.

In addition we do know something at the the time the information is
transferred. The situation is a little complicated because, if we are only
dealing with manipulations at one site and detections at the other site,
then a local hidden variables model could account for the affects.
Each site knows that certain combinations of polarizer angles and 
detections at the distant site have a suitably low probability.
For this knowledge to exist at both sites simultaneously requires the
instantaneous transfer of knowledge in at least one direction.
How could this knowledge not be considered information? 

Paul Budnik
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