X-Message-Number: 13715
From: 
Date: Fri, 12 May 2000 07:41:04 EDT
Subject: X-ray coherence, pulse number andbandwidth in QND

The x-ray bandwidth:

I have said before why the x-rays used in a quantum nondemolition (QND) 
interferometer must have a low energy, in the 500 eV to 2 KeV range so that 
they don't see hydrogen atoms and are absorbed by carbon ones.

I have said too why each beam must have two waves, each one cancelling the 
other everywhere but in a small domain. That domain is a slice giving the 
interferometer precision in the 3rd dimension. A protein complex in a neuron 
junction is 200 nanometers width and there is a mathematical theorem saying 
approximately: If a signal is sampled to two times its highest frequency, 
there is no loss of information. Here, the smallest object, the neuron button 
junction, must be localised with a precision equal to its dimensions, or 200 
nm. The sampling must so be done in 100 nm slices, this is the thickness of 
the domain where the x-ray wave is not near zero. To be sure, that wave 
packet must be many wavelengths thick. Near 1 KeV, the wavelength is near 1 
nm so a 100 nm slice is a perfectly choosen value.

Another length of interest is the so called coherence length, or spatial 
extension of the wave packet of the x-ray photon. If a brain is 20 cm thick, 
we must be able to have a destructive interference on that length and that 
define the coherence length. This is true for a single pass interferometer, 
alas we need up to one million travel in the system, all of them done by the 
same wave. If the total optical path in the interferometer is 10 m long, then 
the coherence length must be 10 000 000 m long or  10 000 km. With a 300 000 
km/s celerity, the wave remains in the interferometer for 1/30th of a second. 
Because that pulse sees only a 100 nm thick slice, a 20 cm brain will needs 2 
000 000 pulses or 60 000 seconds to be mapped. This is far too much and there 
must be many pulses looking at different places at the same time in the 
interferometer. Each pulse must have its own frequency so that it don't 
produces anoying interferences with others.

Here I assume the pulse multiplicity is 1 000, so that a brain reading takes 
only 60 seconds or one minute. In that time, no molecule must move from its 
initial place beyond the 100 nm precision range. That is why that system 
can't read a living brain, mostly in the liquid state. Only frozen brains can 
be read, so this technology is very specific to the task of getting out of a 
cryonics state.


Yvan Bozzonetti.

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