Re: Delayed choice experiment and interstellar signalling

Allen,

You talk as if the article you quote supports your contention that I'm
talking about faster than light signalling. Nothing could be further
from the truth. If you actually thought about what I'm propsing you'd
see that I'm doing a delayed choice experiment but over interstellar
distances. The sender sets up the experiment, the reciever decides
what to measure - clearly delaying the choice - the result of the
measurement is read locally by the sender to determine whether or not
the which way information is read. And the delayed choice experiment
you cited proves that results can be recorded BEFORE the choice is
made to read the which way information. That is, the random number
sequence can be read by the observer of the changing interference
pattern - BEFORE the delayed choice is made.

Clearly the persons receiving the signal from which they choose to
extract the which way information control the outcome of the
interference pattern - which can be read by the sender at the time the
signal is sent BEFORE the which way information is extracted by the
receiver. This constitutes instantaneous signalling back through
time.

That's what delayed choice means.


On Mar 18, 10:49 am, "Allen Thomson" <thoms...@xxxxxxxxx> wrote:
On Mar 18, 2:43 am, "Williamknowsbest" <William.M...@xxxxxxxxx> wrote:

We don't need interstellar civilization to do this experiment.

That's right, the delayed choice experiment has already been carried
out by many. But doing it over large distances provides a means to
create instantaneous signalling. The forward directed beam can be
modulated to signal normally. The which way information can be
extracted or not,determining the outcome of the interference results
at the point the embedded which way information is created.

In fact two interference systems are run in parallel and the embedded
which way information is transmitted in parallel. So, reading both
which way signals collapses both interference patterns - showing a
naive reception. Reading channel A but not chennel B - transmits a
logical -0 Reading B and not A transmits a logical 1 - and not reading
A or B - says the signal was not received by anyone.


No indeed, it can be done in French civilization. But it doesn't mean
you can send signals faster than light, because the light still has to
travel the distance.

Never said faster than light, I said instantaneous signalling. Which
is something entirely different. In fact your references supports my
contention.

A minkowski diagram shows the microwave beam moving forward in time.
The choice of the receiver which parameter to measure determines the
result the sender sees in his interferometer at the time the
interferometer results are recorded - even if the choice of the
receiver is delayed relative to the sender - in this case of
interstellar distances the choice is delayed by years. That doesn't
matter.


Science 16 February 2007:
Vol. 315. no. 5814, pp. 966 - 968

Experimental Realization of Wheeler's Delayed-Choice Gedanken
Experiment

Vincent Jacques,1 E Wu,1,2 Frédéric Grosshans,1 François Treussart,1
Philippe Grangier,3 Alain Aspect,3 Jean-François Roch1*

Yes, this is one reference. The quantum eraser experiment I
referenced at the outset takes this a step further with polarized
light - I take it a step further and use microwaves rather than
optical wavelengths.

Wave-particle duality is strikingly illustrated by Wheeler's delayed-
choice gedanken experiment, where the configuration of a two-path
interferometer is chosen after a single-photon pulse has entered it:

Right. This is more than a thought experiment. Its a real experiment
that has been done and has proven that the choice of whether or not to
read the which way information can be made AFTER the interference
pattern is recorded. Which means that something in the future can
affect something NOW. This is all I'm saying. By a clever
arrangement of two interference experiments and sending embedded which
way information for both experiments to a knowledgeable receiver some
distance away, which of the two the receiver measures can be known
before the receiver measures the which way information - providing a
means for the sender to recieve information from the future -
instantaneously or nearly so - at the time the embedded which way
information is transmitted. The sender can respond to the information
received in this way by modulating a third signal - providing real
time conversation over arbitrarily long distances.

Either the interferometer is closed (that is, the two paths are
recombined) and the interference is observed, or the interferometer
remains open and the path followed by the photon is measured. We
report an almost ideal realization of that gedanken experiment with
single photons allowing unambiguous which-way measurements. The choice
between open and closed configurations, made by a quantum random
number generator, is relativistically separated from the entry of the
photon into the interferometer.

Yes. This says in laymen's terms, the result of the interference
measurement is recorded well before the which-way information is read
by the delayed choice apparatus. Now imagine the photons are
microwave bursts and the delayed choice apparatus is connected to the
interference apparatus by radio telescope and the laboratory extends
some dozens of light years separation - and you have it. The delayed
choice element determines the outcome of the interference element well
after the interference element is read - providing a means for
instantaneous control of telerobotic systems, or instantaneous
communication across interplanetary interstellar or intergalactic
distance - and as a side benefit - signalling through time.

In other words the which way information is beamed to a distant point
some light seconds light minutes or light days away in a way that's
ambiguous to the sender but at the choice of the receiver can
determine to read the which way information or not. Clearly the
receiver of that information can choose to extract the which way
information or not - which changes the record at the sender's location
signalling the sender of what the receiver will do - in essence
sending a bit of information to the sender at the point in spacetime
the interference measurement is made.

By having multiple inteference devices and multiple embedded which way
signals one or more bits can be signalled to the sender by the
receiver in the way described already.

By repeated experiments one after the other, and repeated choices of
what to extract to measure by the receiver,additional bits of
information can be sent to the sender.


1 Laboratoire de Photonique Quantique et Moléculaire, Ecole Normale
Supérieure de Cachan, UMR CNRS 8537, 94235 Cachan, France.
2 Key Laboratory of Optical and Magnetic Resonance Spectroscopy, East
China Normal University, 200062 Shanghai, China.
3 Laboratoire Charles Fabry de l'Institut d'Optique, Campus
Polytechnique, UMR CNRS 8501, 91127 Palaiseau, France.

Yes, I'm familiar with this. It doesn't support your contention that
I'm talking about faster than light travel. In fact is supports what
I'm saying. Certainly interstellar distances are relativistically
separated from the interference device so, its quite easy to see
what's going on there.

But if you would have actually read with comprehension what I wrote
you would see that the quantum eraser experiment is more along the
lines of the sort of delayed choice experiment I'm talking about -
except with microwave equipment obviously and radio telescopes.

Here's a cool article on the sort of thing I'm talking about
http://arxiv.org/PS_cache/quant-ph/pdf/9903/9903047.pdf

And a mroe general reference
http://en.wikipedia.org/wiki/Delayed_choice_quantum_eraser

.

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