Re: Science News - article on Quantum Crypto

[jim bell <jimbell@pacifier.com>]

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At 01:18 PM 2/18/96 -0500, Alexandra Griffin wrote:
>Bob writes:
>
>> Does anyone know if the new in-line optical amplifiers (not switches!) have
>> any effect on quantum crypto messages?
>
>Yes, any active devices in your communications path would be unable to
>function without making some kind of classical measurement on the
>photons involved (e.g. measuring phase relative to a definite test
>angle, if phase is what's being modulated), thereby collapsing the
>wavefunction and spoiling any special properties afforded by being
>able to send photons down the line without "looking at them."  Optical
>repeaters have to pass your signal through an intermediate electronic
>stage anyway, since we have no purely optical valve/transistor
>equivalents (bosons don't interact with each other at all).

I love to be picky about such things.  Yes, I think bosons _DO_ interact 
with each other.  Before all you physics nerds flame me, hear me out:  
Photons, while they have no "rest mass" do indeed "gravitate" (they are 
energy, recall?).  In a reference I can no longer find in my 1970 
Encyclopedia Brittanica, it stated that a cubic mile of sunshine "weighs" 
1/100,000,000 of a milligram.    From another source (or maybe the same 
one?) it stated that the photon "weight" in a cubic centimeter of volume at 
the core of a star such as our sun (or at the core of a nuclear explosion) 
is about 1 gram per cubic centimeter.

Thus, presumably photons self-gravitate, and thus, SOME bosons "interact," 
although admittedly this kind of interaction is a few dozen orders of 
magnitude lower than what you probably intended when you said "Bosons don't 
interact with each other at all."

Jim Bell
jimbell@pacifier.com

Klaatu Burada Nikto

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