Entangled photon messaging
David Jacobitz
faster than light. But they *can* send information, right (read something
about music having been sent across a lab)? So, if you set up a situation
in which it appears that the information should be sent FTL, does it get
sent but slower than light, or does it just not work?
Here's an almost entirely different question. I've read about the theory
that if you could get a traversable wormhole with movable ends, then cause
one end to undergo time dilation, and bring it back to where the other end
is, you would essentially have a time machine. Assuming this theory is
valid (Is it? Unobtainability of such a wormhole aside), could you do the
same thing with a system designed to send information with entangled
photons, such that one stream is time dilated wrt. the other? Or does the
fact that it's light mean that it can't undergo time dilation?
-Dave
Uncle Al
1) Scientific American is not an authoritative source unless you
are a Liberal Leftist with delusions of Kansas. They've already
sprayed sex under the guise of scholarship and compassion to get their
circulation up. When they embrace dieting they will have arrived full
bore Reader's Digest pap.
2) "FTL" quantum tunneling through barriers chirps the signal. The
centroid relocates but the data itself doesn't arrive early. Here's a
hint: There are only three numbers in the superluminal business -
zero, one, and infinity. When stuff falls between the cracks you go
looking for the hidden footnote.
"If we could build..." but we can't. That is why Relativity holds.
If you wish to beat Relativity Special and General you have to bring
forth a theory that embraces them and the empirical observations that
support them, as they did Newton. If you contradict Relativity you
are wrong.
--
Uncle Al
http://www.mazepath.com/uncleal/
http://www.ultra.net.au/~wisby/uncleal/
http://www.guyy.demon.co.uk/uncleal/
(Toxic URLs! Unsafe for children and most mammals)
"Quis custodiet ipsos custodes?" The Net!
Dirk Bruere
Uncle Al <Uncl...@hate.spam.net> wrote in message
news:8ekns4$m1n$1...@Urvile.MSUS.EDU...
> > It seems fairly decided that entangled photons cannot send information
> > faster than light. But they *can* send information, right (read
something
> "If we could build..." but we can't. That is why Relativity holds.
> If you wish to beat Relativity Special and General you have to bring
> forth a theory that embraces them and the empirical observations that
> support them, as they did Newton. If you contradict Relativity you
> are wrong.
But it's not quite that simple.
It depends what is classed as 'information'.
With entangled photons it 'appears' that information is sent >c (instantly,
AFAIK), but it is encoded to appear as a random sequence. The 'key' must be
transported <c in order to get at the 'real' info.
It is interesting as it gives us a view as to what Nature calls information.
Dirk
John Baez
David Jacobitz <djac...@falctech.com> wrote:
> It seems fairly decided that entangled photons cannot send information
>faster than light. But they *can* send information, right (read something
Yes, entangled photons can send information at the speed of
light just like ordinary ones can - they're just a lot more
expensive.
As for sending music across a lab, you may be thinking of
the experiment done by Gunter Nimtz, which used quantum
tunnelling, not entangled photons. For a typical over-hyped
media account of this experiment, try this article in the
1995 April 1 (no joke!) issue of the New Scientist:
http://www.socorro.demon.co.uk/gunter.htm
An excerpt:
"Yet last month an extraordinary development in this tale unfolded
at a special colloquium organised in Snowbird, Utah. Attending the
meeting were some of the leading researchers in this field of
faster-than-light quantum phenomena. To an astonished audience,
Nimtz announced that his team at Cologne had not only measured
superluminal speeds for their microwaves, but had actually sent a
signal faster than light. The signal in question was Mozart's 40th
Symphony. What they did was frequency modulate their microwave source
with the music and then measure how quickly the music arrived after
traversing the forbidden zone in a waveguide. According to Nimtz,
Mozart's 40th hopped across 12 centimetres of space at 4.7 times the
speed of light. What's more, Nimtz actually had a recording to prove
it. To his now bemused audience, he played a tape in which among the
background hiss strains of Mozart could be heard. This was the
"signal" that had travelled faster than light. But that very word
"signal" triggered heated discussion, with some participants
claiming that the symphony could not be regarded as a signal. Among
them was Chiao. "It's not a signal in Einstein's sense because of
the timescales involved. I agree that when the music crosses the
barrier it is shifted forward in time, compared with music that
travels by a conventional path, but only by a very small amount.
It is so small that you can predict what will happen to the music
simply by looking at how the original audio waveform is changing.
There is no threat to causality.""
Of course Raymond Chiao is right, and only someone quite ignorant of
the issues involved would be "amazed" by the results of Nimtz. For
more details, use Deja to look up old articles on sci.physics.research
with keywords such as Nimtz and Chiao. We discussed this issue to
death!