From: Eric Cordian <emc@wire.insync.net>
Date: Thu, 29 Jan 1998 06:01:48 +0800
To: cypherpunks@cyberpass.net
Subject: Re: EPR, Bell, and FTL Bandwidth (fwd)
In-Reply-To: <199801282036.OAA08857@einstein.ssz.com>
Message-ID: <199801282153.PAA09550@wire.insync.net>
MIME-Version: 1.0
Content-Type: text/plain



Jim Choate writes:
 
>> Think of the classical case.  I bake two fortune cookies, one with
>> "FOO" written on the slip of paper inside, and the other reading
>> "BAR." I then put them in a box and shake it for quite a while, until
>> the final state has chaotic dependence upon initial conditions, and
>> cannot be predicted.  I then keep one fortune cookie, and mail the
>> other one to Lucky Green in Tonga.
 
>> Someday in the future, I open my cookie, and instantly know what
>> Lucky will see when he opens his.
 
> True, but your opening your cookie does not *force* Lucky to open his
> at the same time. This is one fault with this model. The 'state' of
> the cookies are not inter-dependant as the polarization of the photon
> pairs are.
 
While it is true that my examining my cookie does not force Lucky to
examine his, the same can be said of a photon experiment, where the
photons can remain in flight for an arbitrary period of time before
being measured.  However, if there is no spacelike separation between
the two measurments, one has not proved non-local collapse.
 
The state of the cookies is highly correlated, since they have
opposite values.  The polarization of the photon pairs is similarly
correlated, as they have equal values.
 
> It isn't instantanous, the correlation existed when they were printed
> and doesn't change.
 
And indeed in the photon case, the entanglement exists when two
photons with correlated wavefunctions are created.
 
> If I destroy one of the cookies it doesn't destroy the other
> spontaneously as would happen in a correlated photon-pair.
 
Nope.  Destroying one of a pair of entangled photons does nothing to
the other.  Just like the cookies.  It's just that measurements on
both photons may be correlated in a way which would seem to suggest
non-local collapse of their combined wavefunction, if a choice of
which of two non-commuting observables to measure is done on the fly.
 
But if I give you one of a pair of entangled photons, I can't make
anything happen to that photon at a distance that you can detect by
doing something to my photon, even though measurements done on both
photons may show a correlation which implies non-local collapse.
 
> Incorrect. The Heisenberg Uncertainty Principle states that in order
> to measure one parameter the other must *necessarily* change because
> they are in actuality different aspects of the *same* characteristic.
 
Not at all.  Position and momentum are like location and frequency of
a wave.  A pure sinusoidal wave exists everywhere on the t axis, and a
function whose support is confined to a small region is a
superposition of a whole range of frequencies.  I cannot make a
waveform which is non-zero simultaneously in an arbitrary small
portion of the both the time and frequency domains.  Similarly I
cannot construct a quantum mechanical wavefunction which is confined
to an arbitrarily small portion of the position and momentum domains.
 
This does not mean that position and momentum are different aspects of
some other dynamical quantity.  Both position and momentum are
fundamental dynamical variables, in and of themselves.
 
>> You can see this easily with three polarizing filters.  If you shine a
>> light through two of them at right angles to each other, it will be
>> completely blocked.
 
> Only if the light has a single polarization. If you shine a circularly
> polarized light through you will in fact see light on the other side.
 
Circularly polarized light is simply a superposition of vertically and
horizontally polarized light of different phases.  It has no magical
ability to make it through two polarizing filters set at 90 degrees to
each other.  (This is an experiment *YOU* can perform at home!)

-- 
Eric Michael Cordian 0+
O:.T:.O:. Mathematical Munitions Division
"Do What Thou Wilt Shall Be The Whole Of The Law"