Quantum entangled-photon Chinese satellite.

[Zenaan Harkness]

On Fri, Aug 05, 2016 at 11:07:13AM +0300, Georgi Guninski wrote:
> On Fri, Aug 05, 2016 at 04:50:37AM -0300, juan wrote:
> > On Thu, 4 Aug 2016 23:33:47 +0000 (UTC)
> > jim bell <jdb10987 at yahoo.com> wrote:
> > 
> > 
> > > If I see a horse running in the prairie, and yet I cannot
> > > capture him, Icannot use him to travel at horse-speed rather than
> > > man-speed.
> > 
> > 	OK, I understand that. But to use your analogy, what's being
> > 	discussed here is not how the horse could eventually be used,
> > 	but whether the horse exists at all. 
> > 
> > 	Is the horse just some mathematical artifact in some mystical
> > 	theory, or is there unambiguous experimental data associated
> > 	with it?
> > 
> >
> 
> Disclaimer: I am lamer in physics.
> 
> I think the analogy shows that FTL (superluminal) speed exist and is
> experimentally observed, this doesn't contradict relativity.
> 
> What contradicts relativity is _communication_ or clock synchronization
> faster than light.

I'll accept the clock synchronisation not being possible FTL, but not
the communication part.

The reason being, that the remote side makes an observation, and
although the entangled photon state change shall be observable at a FTL
time-delta into the future for the other side, the other side cannot
know when to make his observation in order to "read" the bit.

And, the side receiving information can only synchronize according to
the most accurate clock he has at his disposal - which runs at most, at
the speed of light, so he cannot make more than some very large number
of observations --below-- the speed of light, and so i.e. his
observational capacity exists as -slower- than the speed of light.

Thus the basic limitation.


Firstly, I suspect the Chinese (and Google who bought the bullshit on
that "quantum computer" company a year ago) have jumped the gun, as we
are missing at least a second superluminal communication primitive. This
point should be obvious.


A full (e.g. FTL) comms circuit requires a minimum of two primitives,
and at the moment all the quantum boffins have is a single possibly FTL
"primitive" (that is, the purported capacity to read one half of an
entangled photon).

And this, with being not able to determine that you changed the state
(not sure on this assumption), and being not able to determine the
state; "at your end".

"At the other end" however, apparently, the corresponding read action
can be done (but without synchronization yet, we don't have such a
primitive, yet), to determine IF the first side has already performed
its own read/observation action, up to and including the same point in
time as we are doing our read/observation - i.e. "now".

But not into the future (presumably, hey wtf do I know).


So, some yet to be properly modelled substrata of the entangled quantum
universe apparently provides for 'instantaneous' communication, given
the following caveats:
 1 - the time synchronization limits of the two sides
 2 - the source/originating 'observation action' must happen no later
     than the time that the destination/receiving side makes their
     observation (should be obvious)


Physics vs engineering? As in, the physicists are so focussed on the
single qubit, they forgot to state "the obvious"?


I suspect that the physicists and quantum mathematicians may have simply
failed to state the limitations of their new toy in a simple way. May be
they did, I have not read any literature and am dependent on this thread
and possibly a pop sci article some years back.


> IIRC if you point powerful projector at the Moon and move it slightly,
> this light on Moon will move FTL at least from your point of view. 
> Jim's horse was something like this.
> 
> Check wikipedia for faster than light for more examples like this.
>