here is an article i found the other day that seems to have found a new
twist on this subject, this possibly is related to entanglement in some
way, but either way it seems to achieve the desired result
http://www.newswales.co.uk/?section=Education&F=1&id=4703
Welsh scientists find order in chaos
6/10/2001
There is apparently some semblance of order in the weird world of chaos
after all.
In a groundbreaking experiment, electronic engineers at the University
of Wales, Bangor have proven that with two systems in a chaotic
environment, one of them is able to anticipate a signal from the other
before it is even sent.
This extraordinary saga began twelve months when a German physicist, Dr
Henning Voss at the University of Freiburg, controversially suggested
that it was theoretically possible for a state of what he called
"anticipating synchronization' to exist when two duplicate systems exist
within a 'chaotic' or apparently random environment.
In simple terms he was putting forward the notion that under such
conditions it was possible for a duplicate system to anticipate changes
in the original system. It would achieve this by receiving a signal a
fraction of a second before it was actually transmitted.
However, since that time this proposition has remained no more than an
intriguing theory. That is until now. Bringing it firmly into the
practical world of reality, the team at Bangor has just announced a
successful experimental demonstration of it by using light signals
transmitted by chaotic semiconductor lasers.
In an article in this months Physical Review of Letters, the leading
international journal of physics, Professor Alan Shore describes how he
and his colleagues achieved this remarkable feat.
He is an electronic engineer working in the field of laser cryptography
- using lasers in a chaotic state for the secure transmission of data.
In 'traditional' optical transmission, lasers are used to send data via
fibre optic cables in non chaotic form. In this mode the message travels
at the speed of light. Work in transmitting data in chaotic form is
leading towards greater security of transmission.
The data is 'wrapped' in a chaotic signal which is created by using a
simple mirror to reflect light back into the laser. The data can only be
deciphered at the receiver by using an identical chaotic signal to
unravel the signal.
This is possible when the transmitter is used to drive the receiver in
such a way that the chaotic dynamics of transmitter and receiver become
identical - this is termed chaos synchronization.
In the first experimental demonstration of anticipating synchronization,
the laser transmitted a continuous fluctuating signal in chaotic form.
The changes in the pattern of the signal were recorded at the
transmitter and receiver.
Uncannily, the receiver recorded changes in the signal nanoseconds
before the transmitter recorded the transmission of those changes-
thereby anticipating the synchronization of transmitter and receiver.
The anticipation time was found to be equal to the time of flight from
the transmitter to the receiver.
"At present, we cannot fully explain our observations." says Professor
Shore. "We had expected that the anticipation time would depend upon the
time taken for the light to travel between the laser and the external
mirror which is used to drive the laser into chaos. We are currently
developing a theoretical explanation of our observations.
"Synchronization of chaotic external cavity lasers and message
transmission and extraction has been accomplished and has been
demonstrated by a number of groups including our own," said Professor
Shore.
"In order to carry forward this concept into practical use it is now
necessary to confront basic performance issues and, in particular, to
determine the rates at which information can be transmitted. Laboratory
experiments have already confirmed the GHz message transmission
capabilities of semiconductor lasers.
"One of the difficulties faced in developing the use of synchronized
lasers for secure transmission is that there is a finite 'time of
flight' between the transmitter and the receiver.
"As the distance between transmitter and receiver is increased it could
be considered that a basic limitation on system operation can be
established due to the time it takes to synchronize the receiver and the
transmitter. Indeed previous laboratory experimental demonstrations of
laser chaos synchronization have shown that the receiver 'lags' the
transmitter.
"What we have reproduced, however, is the state which was theorized by
Voss of the University of Freiburg, in which when working with chaotic
electronic oscillators, the receiver leads or 'anticipates' the
transmitter."
"The work undertaken in our laboratory has provided the first
experimental confirmation of the appearance of anticipated
synchronization in chaotic external cavity lasers and indeed in any
physical system. A particularly important feature of the experimental
results is the demonstration that the 'anticipation time' is precisely
the 'time of flight' between the lasers.
:The significance of this observation for chaotic communications is
immediately apparent : operating in a regime of anticipating chaos would
ensure that the 'time of flight ' is not a fundamental constraint on
system performance. We are actively exploring a number of other
issuesrelevant to chaotic optical communications which follow from our
observations.
"The essential feature of the chaotic laser system we have studied is
the finite time delay associated with the round-trip time of light in
the laser external cavity. We point out that finite time delays are
ubiquitous.
"We would thus expect that any of those analogous systems which exhibit
chaos should also be liable to anticipating synchronization. We thus
hope that our work will act as a stimulus to explore the opportunities
for observing anticipating synchronization in physical, chemical,
biological and socio-economic systems."
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