Quantum Entanglement is 'Retro-Causal' ??

[Widdekind]

Quantum Entanglement seemingly requires that the soon-to-be entangled particles must first come into causal contact. Now, ever after, those now-entangled particles may drift away, from the "entanglement event" in Space-Time. Yet, since they travel slower than the speed of light, those now-entangled particles will always remain in the (causal) Future Light-Cone of the "entanglement event" in Space-Time. Thus, the world-lines, of all the now-entangled particles, will always be related causally to their mutual "entanglement event".

 

Has it ever been suggested, that the apparent faster-than-light, "non-local" nature of Quantum Entanglement, can be explained, in a 'Retro-Causal' way, as the flow of information, from the first "entanglement observation event", through the entangled world-lines, to the correlated "entanglement observation event" ? To wit, no information actually travels through the space between the now-entangled particles — instead, the information flow "vibrates" along the now-entangled worldlines ??

 

[Mr Skeptic]

Indeed; faster-than-light (which you could call retrocausal) remains a possible explanation for quantum entanglement, even with Bell's Inequality. You can't use it to communicate faster than light however.

[michel123456]

I don't see FTL in this diagram.

[Widdekind]

I don't see FTL in this diagram.

 

According to Wikipedia, to explain the non-locality of Quantum Entanglement, one must invoke velocities of at least ten thousand times the speed-of-light (10⁴c).

 

In my "retrocausal diagram", the information would appear to flow, at these hyper-luminal speeds, "down" the world-line of the one entangled particle, "to" the Quantum Entanglement Event in Spacetime, and then "up" from there along the world-line of the other entangled particle, to the "present", where that information would induce the appropriate quantum behavior in the paired particle.

 

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ANOTHER QUESTION — Breaking Entanglement ??

 

According to Wikipedia, Retrocausality interprets Antimatter as "normal matter moving backwards in time":

 

Time runs left to right in this Feynman diagram of electron-positron annihilation. When interpreted to include

retrocausality

, the electron (marked e

^-

) was not destroyed, instead becoming the positron (e

⁺

) and moving backward in time.

 

Inspired by such an interpretation, "annihilating" a Quantumly Entangled (QE'd) particle could be construed as "sending one of the entangled particles backwards in time", whilst using the resulting antimatter explosion energy to reconstruct "new & freshly laundered matter" (as it were), free from the QE of the previous particle:

 

 

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YET ANOTHER QUESTION — 'Free Will' is Fore-Ordained ??

 

Consider "cooking" a proton, to induce Positron Emission:

 

p

⁺

+

energy

—>

n

+

e

⁺

+

v

_e

 

Then, hold the emitted positron in some sort of magnetic confinement, while you wonder whether to (1) take the positron to the Alpha Centauri star system, and there annihilate it with a local (Alpha Centaurian) electron; or (2) take the positron to the Sirius star system, and there annihilate it with another, also local (Siriusian), electron.

 

From the point of view of 'Free Will', you can choose to do either at your leisure (technology permitting). But, according to Retrocausality, (1) your "positron" is really just an electron moving backwards in time, from the place of its "antimatter annihilation"; and, so, (2) that electron already knows which star system it came from, having already experienced the "bending backwards in time" of its worldline, which you will soon see as the "antimatter explosion" in the ___________ star system, that the electron already knows you chose !!

 

 

Note that the "conservation of worldlines" requires that the "backwards-in-time moving electron" becomes "buried" in the proton, turning it into a neutron (which is completely consistent w/ observations of (free) neutron decay: n —> p⁺+ e^- + energy). (Somewhat similarly, the emitted electron-neutrino v_e [not displayed in the above picture] must have been "buried" in the proton all along.) Indeed, in an anthropomorphized sense, the last thing the puzzled 'positron' ponders, as it speeds out of your magnetic cage, and towards the awaiting proton — where, in yet another burst of energy, its worldline will again "bend backwards in time", and start moving "forwards" as a "regular electron" again — where it will soon be "buried" in the new neutron... is why the heck it just heard you wondering where you'd take it, because it already knew where you'd gotten it, all along !!

Edited March 9, 2010 by Widdekind
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[swansont]

I think a lot of the discussion on entanglement suffers from the error of trying to overlay classical ideas on a quantum-mechanical process.

 

 

 

that electron already knows which star system it came from

 

In the many-worlds interpretation, the electron or positron did come from there. It was your decision to take it there that "split" the world. Free will is preserved.

[Widdekind]

Further Questions:

 

1. Back when all matter was formless energy, in the pre-Big-Bang singularity, did all matter-energy become mutually QE'd, and did that QE survive the fiery birth of the Universe ?
   
2. If antimatter is "negative energy matter", such that it's appearance is always heralded by powerful explosions of energy... then why doesn't "normal" matter spontaneously decay into antimatter, following the energy gradient, as in (free) neutron decay ?
   

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In the many-worlds interpretation, the electron or positron did come from there. It was your decision to take it there that "split" the world. Free will is preserved.

 

Wow — so, "consciousness cleaves reality, from possibility" ? What happens to the "other reality", is it "pruned" from possibility, into ignominy ? Where would the matter-energy come from, to keep creating copious quantities of Cosmoses, every time a consciousness, somewhere & when, came to a new conclusion ??

Edited March 9, 2010 by Widdekind
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[michel123456]

According to Wikipedia, to explain the non-locality of Quantum Entanglement, one must invoke velocities of at least ten thousand times the speed-of-light (10⁴c).

 

 

In this kind of diagram, the Speed Of Light is an angle represented by the diagonal. Faster Than Light is in the white part of the diagram, left & right, the empty space where you put nothing.

Infinite speed is the horizontal line (angle zero). Ten thousand times the speed-of-light is almost horizontal. A hundred of billions billions billions times the SOL is almost the horizontal.

No speed can make circles around the diagram, all speeds end at the horizontal.

So I can understand that entanglement means large speed (in order to reach the horizontal), but I cannot understand in this diagram why Faster Than Light mean "back in time".

[swansont]

Further Questions:

 

1. Back when all matter was formless energy, in the pre-Big-Bang singularity, did all matter-energy become mutually QE'd, and did that QE survive the fiery birth of the Universe ?
   
2. If antimatter is "negative energy matter", such that it's appearance is always heralded by powerful explosions of energy... then why doesn't "normal" matter spontaneously decay into antimatter, following the energy gradient, as in (free) neutron decay ?
   

 

I don't know that anyone can tell you what happened before the big bang, but in general, no. Entanglement is not a default condition of matter/energy. It's fairly hard to achieve (i.e. only under specific conditions) and easy to lose.

 

Antimatter appearance is not always heralded by "powerful explosions of energy." You are proceeding from a false assumption, and you should be thankful, since you have antimatter in your body at this very moment from the beta decays of K-40 and C-14.

 

Wow — so, "consciousness cleaves reality, from possibility" ? What happens to the "other reality", is it "pruned" from possibility, into ignominy ? Where would the matter-energy come from, to keep creating copious quantities of Cosmoses, every time a consciousness, somewhere & when, came to a new conclusion ??

 

 

http://www.lmgtfy.com/?q=many+worlds+interpretation

Edited March 10, 2010 by swansont
fix quote tag

[toastywombel]

Well it is observation that changes or breaks the entanglement right? One has up spin, one has down spin, neither particle completely decides until one is observed.

[swansont]

Well it is observation that changes or breaks the entanglement right? One has up spin, one has down spin, neither particle completely decides until one is observed.

 

Any (or at least many) interaction with the spin will do this. It's hard for me to fathom that the hot dense early universe could have any entanglement survive.

[Widdekind]

Retrocausality can explain Quantum Entanglement from Pair Production (?)

 

According to the brief mention of QM, in the special features section, of the movie Suspect Zero (DVD), "Quantum Entanglement is often observed during the production of pairs of particles" [close paraphrase]. For purposes of discussion, let us presume the appearance of an electron-positron particle pair, "from vacuum". Now, the interpretation, of the positron, as the electron "moving backwards in time", seems to say, that the Pair Production / Pair Annihilation, of the electron-positron pair, represents a single electron "circulating in (space-)time":

 

 

 

Retrocausality can explain Black Hole Radiation from Pair Production (?)

 

Physicist Stephen Hawking described the Quantum mechanism, which gives rise to Black Hole Radiation. When Pair Production happens sufficiently close to the Event Horizon of the Black Hole, one of the particles of the pair (our positron, say) falls into the Black Hole, while the other particle (our electron, say) escapes to infinity — carrying away its energy from the Black Hole.

 

Now, the interpretation, of the positron, as the electron "moving backwards in time", leads to the startlingly straightforward statement, that our electron "simply" escapes from the far future Singularity, and crosses the Event Horizon, by "going backwards in time". It then just continues on, out to infinity, carrying away its energy from the Black Hole:

 

 

But, wouldn't this imply, that if the electron fell into the Black Hole, that the Black Hole's mass should increase, since the "escaping positron" is "really" just an electron, "falling into the Black Hole while going backwards in time" ??

 

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Does Retrocausality suggest a scheme for (hypothetical) Antimatter Rocket ??

 

Please ponder observing an electron & positron, approaching each other from opposite directions (in the Lab-Frame). Surely, the radiation released, by their "(mini) explosive annihilation", is Isotropic (??).

 

But, don't "sharp & sudden" bends, in the trajectories of particles, produce "directed", "columnated", "synchrotron" sorts of radiations ?? So, recall the Retrocausal interpretation of positrons, as simply "electrons moving backwards in time". Then, the "sharpest kink" you could put, into the "backwards-in-time-bending" worldline of the electron, would be to basically "reverse the course" of the electron through Space-Time -- (nearly) inverting its 4D velocity vector ( [math]\left( \vec{v},c \right) \rightarrow \left( -\vec{v},-c \right)[/math] ), so that the "positron" was sent "backwards in time" almost along the same worldline that the electron came in on. Could such a scheme conceivably create a "columnated" release of radiation (which would potentially provide rocket thrust) ?? Are there any indications that this could, or could not, be the case ?? (Wouldn't this assumption, at least obey Conservation of Momentum, w/ the two parallel gamma rays carrying off the incident momentum, of the parallel positron-electron beams ??)

 

 

 

 

Note that this 'Retrocausal' interpretation, seemingly says, that all of the "positrons", in the spaceship's "positron fuel tank", are actually the very same electrons then in the "electron fuel tank"... after those electrons have been "fired, exploded, & recovered [as 'positrons']"... at some point in the future (when, of your own Free Will, you choose to engage your Antimatter Rocket thrusters) (?!). Furthermore, the "positron-electron" Pair Creation that you (presumably) used to fill your fuel tanks, would -- in the Retrocausal interpretation -- actually represent merely the point were the positron "electrons moving backward in time" were switched to moving forward in time. To wit, between that Pair Creation (to fill the tanks), and the Pair Annihilation (emptying the tanks to provide propulsion), your electrons would simply "circulate in time".

Edited March 18, 2010 by Widdekind
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[swansont]

Please ponder observing an electron & positron, approaching each other from opposite directions (in the Lab-Frame). Surely, the radiation released, by their "(mini) explosive annihilation", is Isotropic (??).

 

In the CoM frame, the two photons will go in opposite directions. In the event that you have three photons, momentum will still be conserved; I'm not sure there is a requirement that the photons have equal energy in this case, so they will not follow any particular spacing.

 

 

But, don't "sharp & sudden" bends, in the trajectories of particles, produce "directed", "columnated", "synchrotron" sorts of radiations ??

 

"Accelerations" of charged "free particles" causes bremsstrahlung. But an electron and positron in a bound state ("positronium") are not free particles. Annihilation radiation and bremsstrahlung are separate phenomena.

 

BTW, it's "collimated"

[Widdekind]

In the CoM frame, the two photons will go in opposite directions. In the event that you have three photons, momentum will still be conserved; I'm not sure there is a requirement that the photons have equal energy in this case, so they will not follow any particular spacing.

 

Could you use particle accelerators, to accelerate that CoM frame, swiftly sternwards, relative to the spaceship ?

 

 

 

 

"Accelerations" of charged "free particles" causes bremsstrahlung. But an electron and positron in a bound state ("positronium") are not free particles. Annihilation radiation and bremsstrahlung are separate phenomena.

 

BTW, it's "collimated"

 

 

woops, thanks !

[swansont]

Bremsstrahlung is proportional to the square of the acceleration and depends strongly on the energy of the particles. IIRC it is peaked perpendicular to the direction of the acceleration, so it will not be emitted the way you have described. And photons have relatively little momentum anyway, so as propulsion this is probably not a viable method. The thrust from simply accelerating the charges will be much larger, i.e. ion propulsion.

[Widdekind]

Testing Retrocausality -- an "Antiparticle Paradox" ?

 

If an antiparticle is really a "regular particle moving backwards in time", then, in any series of measurements you apply to an antiparticle, it will "witness" the last of them first, and the first of them last (?!).

 

Thus, as a potential 'paradox', perhaps it's possible to (1) observe the antiparticle, to determine its state ("spin up"); (2) some time later, manipulate that antiparticle, to be the opposite of that "previously" determined state ("spin down").

 

 

What would happen ??

 

EDIT: Actually, the "antiparticle paradox" is no paradox at all. For, if the antiparticle actually is "moving backwards in time", it would experience time "backwards". So, your "manipulation" to put the antiparticle in a "spin up" (say) state... would be seen by the antiparticle, in reverse, as your forcing it to go "spin down". Thus, your "observation ('spin down') & manipulation ('spin up')" would be perceived by the antiparticle, in reverse, as "manipulation ('spin down') & confirmatory observation ('spin down')". Thus, this author's suggested apparent "paradox" is no paradox at all.

 

 

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Bremsstrahlung is proportional to the square of the acceleration and depends strongly on the energy of the particles. IIRC it is peaked perpendicular to the direction of the acceleration, so it will not be emitted the way you have described. And photons have relatively little momentum anyway, so as propulsion this is probably not a viable method. The thrust from simply accelerating the charges will be much larger, i.e. ion propulsion.

 

From a "conventional perspective", such a "double-barreled electron-positron cannon" perhaps produces propulsion, from the ejection of pair of particles (?). From a "Retrocausal perspective", the "cannon" perhaps produces propulsion, "firstly" from the ejections of the electrons, which stream swiftly sternward from the spaceship... before "bouncing off the gamma-ray explosion" (rather roughly speaking)... and, then, "secondly", streaming swiftly "back aboard the spaceship by the other barrel" as positrons ("electrons moving backwards in time")... where they impart the "other half of the momentum" to your spaceship, as propulsion, as they "decelerate into a soft-landing in your positron fuel tank" when they interact with (what you think is your) "positron accelerator apparatus" (?).

 

However, it seems to me, that the propulsion produced by such as system, would "wind up" being -- by whatever way one looked at it -- merely made by the ejection of the high-energy ions, essentially as in a standard Ion Drive. So, if you could already accelerate electrons to such high velocities & energies, there might not be much improvement made, by adding a "second positron barrel" to the design, over simply a "second electron barrel" (or, merely more electrons from the original thruster). So, a standard Ion Drive seems a sounder design.

Edited March 20, 2010 by Widdekind
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