update.356 (fwd)

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>From physnews@aip.org Tue Jan 27 15:31:03 1998
Date: Tue, 27 Jan 1998 08:46:26 -0500
From: physnews@aip.org (AIP listserver)
Message-Id: <199801271346.IAA15741@aip.org>
To: physnews-mailing@aip.org
Subject: update.356


PHYSICS NEWS UPDATE                         
The American Institute of Physics Bulletin of Physics News
Number 356 January 27, 1998   by Phillip F. Schewe and Ben Stein

LOCALIZATION OF LIGHT has been achieved by an Amsterdam-
Florence collaboration (contact Ad Lagendijk, adlag@phys.uva.nl). 
Consider the movement of light through a  diffuse medium such as
milk, fog, or sugar.  The light waves scatter repeatedly, and the
transmission of light decreases as the light gets reflected. In the
Amsterdam-Florence experiment something different happens.  By
using a gallium-arsenide powder with a very high index of
refraction but with very low absorption at near infrared (wavelength
of 1064 nm), the researchers were, in a sense, able to get the light
to stand still.  That is, the light waves get into the medium and
bounce around in a standing wave pattern, without being absorbed. 
This is the first example of "Anderson localization" for near-visible
light.  This medium is not what would be called a "photonic
bandgap" material (analogous to a semiconductor for electrons) but
more like a "photonic insulator." (Wiersma et al., Nature, 18/25
December 1997; see also www.aip.org/physnews/graphics)

QUANTUM EVAPORATION occurs in a new experiment when a
beam of phonons (little pulses of sound issuing from a warm
filament) inside a pool of superfluid helium-4 is aimed at the liquid
surface from below.  In analogy with the photoelectric effect (in
which light ejects electrons from a surface), the phonons pop helium
atoms up out of the liquid.  By measuring the momenta of the
phonons and the evaporated atoms, one can determine that the
atoms originally had zero momentum parallel to the surface,
demonstrating directly (for the first time) that the He-4 atoms had
been part of a Bose-Einstein condensate (BEC), in which the atoms
fall into a single quantum state.  Theories of superfluid He-4 had
supposed that the atoms reside in a BEC state, but this had not been
experimentally verified until now.  The researcher, Adrian Wyatt
of the University of Exeter,  believes this method can be used to
generate beams of coherent helium atoms (an "atom laser" effect). 
(Nature, 1 January 1998.)

ANOTHER VERSION OF QUANTUM TELEPORTATION is
being published by researchers in Italy and England (Francesco
DeMartini, University of Rome, demartini@axcasp.caspur.it).  Like
the Innsbruck teleportation scheme published several weeks earlier
(Update 351), this demonstration employs a pair of entangled
photons.   Whereas the Innsbruck experiment teleported the
polarization value of a third, distinct "message photon" to one of
the entangled photons, the Rome scheme encodes one of the
entangled photons with a specific polarization state and transmits
this state to the other entangled photon. Although different from the
Innsbruck experiment (which had a 25% teleportation success rate)
and the original theoretical proposal for teleportation, this scheme
works 100% of the time if the receiver applies the right
transformations on the second photon. (D. Boschi et al., upcoming
article in Physical Review Letters).  In another, theoretical paper,
Sam Braunstein of the University of Wales (Bangor) and Jeff
Kimble of Caltech propose an experimental method for extending
quantum teleportation from transmitting discrete variables such as
polarization to transmitting continuous variables like the amplitude
of the electric field associated with a light wave. (Braunstein et al.,
Phys. Rev. Lett., 26 January 1998.)

Phelix wrote:

> I remember seeing on one of those science specials on The learning channel
> (or mabye the Discovery channel) that a professor did figure out
> (accidentally) how to send information faster than light.  The only thing I
> remember about it was the the signal was some kind of music.

http://i02aix1.desy.de/~mpoessel/nimtzeng.html
http://www.npl.washington.edu/AV/altvw75.html
http://www.uni-koeln.de/~abb11/
http://www.aei-potsdam.mpg.de/~mpoessel/nimtzeng.html
http://www.fringeware.com/msg/1996/msg00155.html

On 28 Jan 1998 12:24:30 -0600, Tim May <tcmay@got.net> wrote:

>I personally doubt that any flat spacetime topology (e.g., wormholes
>excepted) will admit any FTL signals. A lot of things would dramatically
>change if FTL communication existed...not the practical "communication"
>issues, which are human social minutiae, but issues about synchronization
>of reference frames and causality violations.

I remember seeing on one of those science specials on The learning channel
(or mabye the Discovery channel) that a professor did figure out
(accidentally) how to send information faster than light.  The only thing I
remember about it was the the signal was some kind of music.

I remember now, it was a special on time travel on a month ago.  Anybody
catch it?

-- Phelix

Tim May wrote:

> Nothing in quantum teleportation has been shown to propagate signals
> faster than light. (If you don't believe me, look into it. Start by
> reading the FTL discussions about Bell's Theorem.)

True, but there are some other interesting effects which could be
explained by FTL communication, such as the fact that light diffracted
through two slits shows an interference pattern, even though one of
the slits is farther away than the light travel time from where the
pattern appears.

Then there's the fact that light appears to propegate faster in a region
of space 'starved' of virtual particles by the casimir effect.  That one
is a favorite among warp drive theorists. :)

Phelix wrote:

> I remember seeing on one of those science specials on The learning channel
> (or mabye the Discovery channel) that a professor did figure out
> (accidentally) how to send information faster than light.  The only thing I
> remember about it was the the signal was some kind of music.

http://i02aix1.desy.de/~mpoessel/nimtzeng.html
http://www.npl.washington.edu/AV/altvw75.html
http://www.uni-koeln.de/~abb11/
http://www.aei-potsdam.mpg.de/~mpoessel/nimtzeng.html
http://www.fringeware.com/msg/1996/msg00155.html

>ANOTHER VERSION OF QUANTUM TELEPORTATION is
>being published by researchers in Italy and England (Francesco
>DeMartini, University of Rome, demartini@axcasp.caspur.it).  Like
>the Innsbruck teleportation scheme published several weeks earlier
>(Update 351), this demonstration employs a pair of entangled
>photons.   Whereas the Innsbruck experiment teleported the
>polarization value of a third, distinct "message photon" to one of
>the entangled photons, the Rome scheme encodes one of the
>entangled photons with a specific polarization state and transmits
>this state to the other entangled photon. Although different from the
>Innsbruck experiment (which had a 25% teleportation success rate)
>and the original theoretical proposal for teleportation, this scheme
>works 100% of the time if the receiver applies the right
>transformations on the second photon.

I wonder how far off use of this technique for interplanetary rovers might
be (10 years, 20 years)?  Remote (Earth) rover manipulation is tedious at
best due to several minutes (or an hour or more to the outer planets) of
propagation delay.  Autonomous rovers need enough smarts built-in to handle
unexpected situations, a non-trivial problem.  An alternative is to
establish a link using entangled photons. If a simple approach to saving
these entangled states during signal transit, in both directions, were
found instantaneous communication and simplified remote control would be a
reality.

Of course one needn't stop there.  If entangled states could be stored for
several years, instantaneous communication with neighbooring stars is a
real possibility.  Coupled with advances in mind-machine science it might
someday be possible to explore, first-hand, our local portion of the galaxy
without leaving earth, or upload/download one's consciouness to vessels in
remote locations.

Speaking of which, do the current SETI programs check for signal modulation
using polarization.  If we've discovered this trick, sure so have other
intelligent life forms.  Most natural sources of radiation tend to
unpolarized, so a rapidly flucuating polar modularion might easily appear
to be noise.

--Steve

Steve Shear postulates:

> Of course one needn't stop there.  If entangled states could be stored
> for several years, instantaneous communication with neighbooring stars
> is a real possibility.

And in whose local Lorentz frame would such communication be
"instantaneous"?

> Coupled with advances in mind-machine science it
> might someday be possible to explore, first-hand, our local portion of
> the galaxy without leaving earth, or upload/download one's consciouness
> to vessels in remote locations. 

Uh, no.  The operators for corresponding observables at both ends of such
an experiment commute, so it is not possible to transmit information
non-locally using such an apparatus. 

This was discovered when the first experiments to verify the
Einstein-Rosen-Podolsky effect were done.  You need the results of
measurements on the opposite end to decrypt the information at the end you
are at. 

The Dancing Wu-Li Masters are closed for business. 

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

>This was discovered when the first experiments to verify the
>Einstein-Rosen-Podolsky effect were done.  You need the results of
>measurements on the opposite end to decrypt the information at the end you
>are at.

I guess I'm over my head in such matters.  From my, admitedly, shallow
understanding of wave function collapse, etc., I was under the apparent
misimpression that once collapsed (e.g., by Alice entangling a 'modulation'
photon M (of a known polarization) with one member (photon A) of an
entangled pair, one of which was sent to Alice and the other (photon B)
which was sent to Bob, photon B's polarization state was determined and
could not subsequently be altered by Bob's measurement with his receiver.
Could you recommend a good article which explain this paradox to a
non-quantum mechanic?

--Steve

At 8:34 PM -0800 1/27/98, Tim May wrote:
>At 7:56 PM -0800 1/27/98, Steve Schear wrote:
>>Of course one needn't stop there.  If entangled states could be stored for
>>several years, instantaneous communication with neighbooring stars is a
>>real possibility.  Coupled with advances in mind-machine science it might
>>someday be possible to explore, first-hand, our local portion of the galaxy
>>without leaving earth, or upload/download one's consciouness to vessels in
>>remote locations.
>
>Who's your supplier?

EPR Pharmaceuticals.  Want their address?

--Steve

At 7:56 PM -0800 1/27/98, Steve Schear wrote:

>I wonder how far off use of this technique for interplanetary rovers might
>be (10 years, 20 years)?  Remote (Earth) rover manipulation is tedious at
>best due to several minutes (or an hour or more to the outer planets) of
>propagation delay.  Autonomous rovers need enough smarts built-in to handle
>unexpected situations, a non-trivial problem.  An alternative is to
>establish a link using entangled photons. If a simple approach to saving
>these entangled states during signal transit, in both directions, were
>found instantaneous communication and simplified remote control would be a
>reality.

Nothing in quantum teleportation has been shown to propagate signals faster
than light. (If you don't believe me, look into it. Start by reading the
FTL discussions about Bell's Theorem.)

I personally doubt that any flat spacetime topology (e.g., wormholes
excepted) will admit any FTL signals. A lot of things would dramatically
change if FTL communication existed...not the practical "communication"
issues, which are human social minutiae, but issues about synchronization
of reference frames and causality violations.

>
>Of course one needn't stop there.  If entangled states could be stored for
>several years, instantaneous communication with neighbooring stars is a
>real possibility.  Coupled with advances in mind-machine science it might
>someday be possible to explore, first-hand, our local portion of the galaxy
>without leaving earth, or upload/download one's consciouness to vessels in
>remote locations.

Who's your supplier?

--Tim May


The Feds have shown their hand: they want a ban on domestic cryptography
---------:---------:---------:---------:---------:---------:---------:----
Timothy C. May              | Crypto Anarchy: encryption, digital money,
ComSec 3DES:   408-728-0152 | anonymous networks, digital pseudonyms, zero
W.A.S.T.E.: Corralitos, CA  | knowledge, reputations, information markets,
Higher Power: 2^2,976,221   | black markets, collapse of governments.
"National borders aren't even speed bumps on the information superhighway."