X-Message-Number: 19368
From: 
Date: Sat, 29 Jun 2002 10:16:10 EDT
Subject: Brain reader, intensity interferometer

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I have already wrote a  number of messages concerning the need for reading 
the contents of a brain in a nondestructive way. Indeed, it appears more and 
more that stem cells will make it possible to regenerate any body part. At 
least if one is only interested by the functional aspect. The case of the 
brain is separate: It must not only function, but set out again where it had 
stopped. It is of no use to start anew from zero and end up with a twin of 
the original person.     
    
In brain reading, two scales of analysis seem interesting: the one of 
connections between neurons and that of the molecular compexes of the 
synaptic buttons. The first is on the level of the micrometer, the second of 
a few tens of nanometers. The first is interesting for two reasons: It gives 
the wiring map of the brain and then the localization of the points of 
contact between neurons. This last element is useful for calculations 
necessary to reconstitute the brain, these calculations are considerable and 
the fact of being able to reduce the zone where they must be done is very 
significant. For that first scale, the magnetic imagery by raisonnance of 
helium 3 nuclei polarized per laser seems the solution (He3 NMR). 

The second scale of analysis, the finest, has more  problems. The magnetic 
imagery by raisonnance would ask for months of recording, if not more. X-rays 
"dentists" (Photons of 60 keV) would do too many damage by radiations. The 
best solution seems to be the use of "soft" x-rays in an interferometer of 
the Michelson type with quantum nondemolition (QND). The probem is to get 
these x-rays with a very big coherence length, which implies a nuclear laser. 


I think that in approximately 30 years this device can be developed, either 
by exciting nuclei with entangled optical photons, or with devices of the 
thermonuclear type. Those can be quasi military: Theta pinch or compression 
by 2 stage guns and hollow-charges with hydrogen-xenon, or more exotic,  
quantum states carried out in a quantum calculator and teleported on the 
thermonuclear fuel (black magic).    
    
Another possibility, completely different would be to exploit an 
interferometer with particles, or interferometer with 2x2 waves. It would be 
then possible to exploit  millimetric waves. This kind of device can extract 
information on a scale independent of the wavelength of radiation used, a 
millimeter-length wave can be thus used to look at objects 100 000 times 
smaller. In fact, even a device with two waves can do that if  one takes into 
account the evanescent wave. The problem is then that of the proximity of the 
source. This soution is not valid for an image in 3 dimensions. 

To give some idea about a four wave interferometer, let us say that the 
interferometer with 2 waves produces interference fringes whereas the system 
with 4 waves counts correlations time in particle hits. In the interferometer 
with 4, or rather, 2 X 2 waves, what interferes are squares of amplitudes, 
therefore density of probability of presence of particles. When one 
integrates that over a defined time duration, one has a number of particles, 
for example a light intensity. Such intensities are thus compared. The key of 
the system is to have a rather fast recorder. By spreading out the beam of 
light over a CCD it is possible to have a high temporal resolution. If one 
sweeps 1000 times a second a  mega pixels CCD, we are on the level of the 
nanosecond time resolution. I considered this system a few years ago, but 
such CCD were on the level of the laboratory at best. They are now in general 
consummer electronics products. In approximately 3 hours, it would be 
possible to obtain an image with a resolution of about 10 microns. To gain 3 
orders of magnitude, it would take a time 1 milion time longer, that is to 
say nearly 500 years! One obviously needs larger sensors or more rapids 
systems. 

Each time one gains a factor 10 on the speed, one gains a factor 100 over the 
time of observation. For example by juxtaposing 10 CCD, with a sweeping 10 
times faster, a brain can be analyzed in 5 years instead of 500. 

Theoretically, it is still possible to gain a factor 100 in speed, which 
would bring the complete analysis in a few hours. The current situation does 
not make it possible to build a brain reader, on the other hand, the 
technological development should produce the elements necessary some years 
from now. So, it seems desirable to establish a technology in this field, 
with intermediate interferometers which would make it possible to develop the 
software necessary to the rebuilding of the brain picture

The original version of that text was in french, it was then translated by 
Alta-Vista Systrans one line service and combed a lot to remove the worst 
errors.

Yvan Bozzonetti.
 

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