Entanglement Theory Query

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Entanglement Theory Query

Postby Event Horizon on September 8th, 2018, 8:44 pm 

I didn't want to start a whole thread, but couldn't find an existing home for it. Its definitely physics tho.

My query is, what happens to an entangled pair if one of the pair is annihilated? How does the pair react? Does the paired photon have a default state when its' pair is destroyed?

If information travels instantaneously, it might be because it is neither a wave or a particle and is not restricted by Einsteinian physics in some respect.

What do we and dont we know as things stand?
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Re: Entanglement Theory Query

Postby mitchellmckain on September 9th, 2018, 1:09 am 

Event Horizon » September 8th, 2018, 7:44 pm wrote:My query is, what happens to an entangled pair if one of the pair is annihilated? How does the pair react? Does the paired photon have a default state when its' pair is destroyed?

The devil is in the details. An annihilation is an interaction. If there is any way in which this interaction depends upon the entangled state then this could easily count as a measurement of that state and thus a measurement of the other particle would have to correlate with that.

For example... if we are talking about two electrons with entangled spins and one annihilates with a positron whose spin is measured then the spin of the electron effects how the annihilation proceeds, i.e. whether it produces two photons or three photons because of angular momentum conservation.

Event Horizon » September 8th, 2018, 7:44 pm wrote:If information travels instantaneously, it might be because it is neither a wave or a particle and is not restricted by Einsteinian physics in some respect.

There is no such thing as the instantaneous travel of information. No information is involved. There is only the correlation of simultaneous random events where it is impossible to say which happened first. You can only imagine one happening first and thus in your imagination causing the measurement of the second electron. But imagining the other happening first is equally valid and thus in your imagination causing the measurement of the first electron. But in reality neither happens first and there is no traveling of information from one to the other. The most you can say is that there is a non-local aspect to reality -- one that can make distant random events correlate with each other.
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Re: Entanglement Theory Query

Postby bangstrom on September 9th, 2018, 3:37 am 

mitchellmckain » September 9th, 2018, 12:09 am wrote:
There is no such thing as the instantaneous travel of information. No information is involved. There is only the correlation of simultaneous random events where it is impossible to say which happened first.


I don’t quite agree with your explanation. Your “correlation of simultaneous events” involves the instant, two-way exchange of a single quantum bit of information. Some object to to the term “information” because a single bit of quantum information is insufficient to serve as a two way exchange of information as we customarily think of it but the term “information” correctly applies to either entanglement events or classical signaling and signaling between entangled particles involves the instant exchange of information. The terms “quantum information” or “classical information” can be used to distinguish between the two.

At our macro level, we can clearly distinguish between the order of events but, at the quantum level, you are right that there is often no such thing as before and after.

This article describes an experiment that demonstrates some of the counter intuitive nature of quantum non-locality.
http://www.sciencemag.org/news/2013/05/ ... -same-time
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Re: Entanglement Theory Query

Postby hyksos on September 9th, 2018, 1:40 pm 

Say we have two entangled photons and they have gone their separate ways.

1. Alice's photon.

2. Bob's photon.

If Bob's photon is annihilated, that would count as a 'measurement' and we would expect that the entanglement would be destroyed. The state of Alice's photon would adopt a particular eigenstate (=have no interference pattern). In simpler language, Alice's photon "collapsed" out of a superposition of states.

But the story gets worse (...perhaps to no one's surprise). We might ask that if alice's photon has been collapsed, then once collapsed, always collapsed? Maybe this is what you were really asking in your OP. {clarification here}

Instead of just absorbing photons like good high school students, lets actually try to destroy Bob's photon. In this sense we will measured Bob's photon, but then annihilate that information we gained from being retrieved again. We can achieve this feat by re-entangling Bob's photon with another third photon, (say, Stephen's photon) and so we don't know what they are doing collectively, and therefore cannot know what they are doing individually. We will perform our "destruction" after having measured the state of Bob's photon.

What happens to the wayward Alice over there? Once collapsed, always collapsed? It turns out that Alice's photon will regain her interference pattern. That is to say, because we destroyed any hope of learning about the state of Bob's photon, Alice will go back into a superposition. She will literally re-entangle herself with Bob's state. (...as if the act of destroying Bob reached back in time and changed the --- )

This is absolutely crazy. It not only flies in the face of our common sense -- it bends our common sense over its knee and spanks its butt red. Despite the horrific trauma this idea inflicts upon common sense, it has actually been performed in labs. It is a Delayed-Choice Quantum Eraser.

The universe actually acts like this.
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Re: Entanglement Theory Query

Postby mitchellmckain on September 9th, 2018, 9:13 pm 

bangstrom » September 9th, 2018, 2:37 am wrote:I don’t quite agree with your explanation. Your “correlation of simultaneous events” involves the instant, two-way exchange of a single quantum bit of information. Some object to to the term “information” because a single bit of quantum information is insufficient to serve as a two way exchange of information as we customarily think of it but the term “information” correctly applies to either entanglement events or classical signaling and signaling between entangled particles involves the instant exchange of information. The terms “quantum information” or “classical information” can be used to distinguish between the two.

Defining your way around the facts of physics is nothing but empty semantics.

bangstrom » September 9th, 2018, 2:37 am wrote:At our macro level, we can clearly distinguish between the order of events but, at the quantum level, you are right that there is often no such thing as before and after.

Incorrect, this has absolutely NOTHING to do with quantum physics and everything to do with the space-time structure of the physical universe. There simply is no objective temporal ordering between events separated by space-like distances -- thus any such ordering is in our imagination only.

bangstrom » September 9th, 2018, 2:37 am wrote:This article describes an experiment that demonstrates some of the counter intuitive nature of quantum non-locality.
http://www.sciencemag.org/news/2013/05/ ... -same-time

This is not a counter-example, because it is meaningless to suggest that a particle is in a superposition which is entangled with a particle which is not in a superposition. If you measure the first particle then the decoherence affects any superposition entangled with it. The moment you measure particle one, particle two is not in a superposition and thus when interacts with particle three you have the decoherence of that superposition as well and particle four being entangled with particle three is no longer in a superposition either. Yeah all the correlations work out but there is nothing surprising in any of this. Frankly they are just equivocating between the terms entanglement and mere causality.

Yes, superpositions can be non-local but its decoherence involves no transmission of information, because there is no information content in random results.
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Re: Entanglement Theory Query

Postby mitchellmckain on September 9th, 2018, 10:05 pm 

The Delayed-Choice Quantum Eraser experiment shows the foolishness of thinking this is about any information being transmitted for then you are suggesting that information is being sent into the past which is absurd. Indeed any suggestion that information is being sent over space-like distance is essentially equivalent to this kind of imagined time travel because the space-time structure of the universe makes them the same thing.

So what is happening in the Delayed-Choice Quantum Eraser experiment? What we learn is that when particles are entangled then they do not interact with other things independent of each other, but rather as two parts of a single thing. I should say, however, that the use of the term "delayed-choice" is a bit misleading, suggesting that we are deciding how to measure the second of the entangled particles after the first has already made a dot on the D0 screen. In reality no such thing is happening. We are simply separating out the data at D0 for those whose entangled particle end up measured in the two different ways. To be sure this result is still very weird and counter our common sense of how the world works.

There is also something I am curious about regarding the Delayed-Choice Quantum Eraser. It only gives a comparison of total path lengths. I would want to compare the path length to D0 with the path length to the beam splitters and check whether this makes any difference. It probably doesn't make any difference but I would want to check and make sure.
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Re: Entanglement Theory Query

Postby bangstrom on September 10th, 2018, 3:53 am 

mitchellmckain » September 9th, 2018, 8:13 pm wrote:
Incorrect, this has absolutely NOTHING to do with quantum physics and everything to do with the space-time structure of the physical universe. There simply is no objective temporal ordering between events separated by space-like distances -- thus any such ordering is in our imagination only.

The implication of this is that the entire physical universe as we observe it exists “ in our imagination only.” Who can say that is wrong?

I fail to see how you can separate “the space-time structure of the physical universe” from quantum physics. QM underlies all of the former. What we observe in the macro world is many, many quantum events ‘averaged out’.

mitchellmckain » September 9th, 2018, 8:13 pm wrote:
Yes, superpositions can be non-local but its decoherence involves no transmission of information, because there is no information content in random results.


You are not alone in objecting to calling quantum decoherence “information” because the signal informs the receiver of the outcome of a random event that the signaling particle has no control over but the receiver responds with an appropriate, “Got the message.” so an exchange of quantum information satisfies nearly everyone’s concept of what qualifies as an exchange of “information.” The initiating event may be random but the signal sent and received is not random. Long ago QM adopted “quantum information” as an acceptable term.

https://en.wikipedia.org/wiki/Qubit :
“In quantum computing, a qubit (/ˈkjuːbɪt/) or quantum bit (sometimes qbit) is the basic unit of quantum information — the quantum version of the classical binary bit physically realized with a two-state device. A qubit is a two-state (or two-level) quantum-mechanical system, one of the simplest quantum systems displaying the weirdness of quantum mechanics. Examples include: the spin of the electron in which the two levels can be taken as spin up and spin down; or the polarization of a single photon in which the two states can be taken to be the vertical polarization and the horizontal polarization. In a classical system, a bit would have to be in one state or the other.”
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Re: Entanglement Theory Query

Postby hyksos on September 10th, 2018, 9:26 am 

So what is happening in the Delayed-Choice Quantum Eraser experiment?

I'm not going to disagree with how you answered this question , in spirit.

But there is a better answer. The DCQE is a clean result of the fact that the Schroedinger Wave is continuous in time.

The Schroedinger Wave is both continuous in space and continuous in time. Its continuous-ness in space dictates the double slit result, and also thin-film interference.



Thin-film interference. : Place a piece of reflective glass over a mirror at microscopic gaps comparable to the wavelength of laser light you shine at it. Make the laser very dim. A single photon has a choice to either reflect totally off the top of the glass, or to refract through the glass, hit the mirror, reflect back up and go back out the top glass again. So it can either reflect off the top, or transmit to below.

Image

We can demonstrate that the distance between the top glass the mirror dictates the probability of the reflection. We can 'tune' the distance so that 100% of the photons transmit and bounce off the mirror. And we can 'tune' the distance so that 100% of the photons reflect off the top of the glass. We can tune any 60/40 , 50/50 probabilty to our heart's content.

What is happening in the situation in which 100% of the photons reflect off the top glass? How did they "know" the mirror was down there, if they never went down there to interact with it? The answer is the photons don't "know" anything at all. . . but the Schroedinger wave does know there is a mirror. Because the Schroedinger Wave knows everything.

Ψ

Ψ not only knows where everything is right now, it also contains information about where everything will be in the future. Because Ψ is continuous (and "differentiable" if you prefer) it must necessarily carry information about the past as well.

This is all very spook-bats to our common-sensical notions of materiality and physicality. But things like Entanglement and Delayed-Choice Erasers are clean, neat consequences of the orthodox formulation of Quantum Mechanics. This means there were men in Europe who knew about this as far back as 1929. YOu have to appreciate how vociferous Albert Einstein was in his rejection of QM.

To be a little more precise : Anyone who claims that the DCQE would not work as described (with retrocausality and that entails) then such a person would necessarily be suggesting that the collapse of Alice's photon causes a discontinuity in Ψ. There is no wiggle room. Either you agree that Alice's photon goes back into unitary evolution, or you necessarily are implying that Ψ has a discontinuity in it where her photon collapsed into an eigenstate. Thus DCQE is a "clean , neat" consequence of Ψ not containing mysterious discontinuities.

Even more precise "Unitary evolution" corresponds to the situation in which a measurement is not made, and a single photon acts according to wave mechanics, with all the requisite interference patterns. "Eigenstate" corresponds to the photon "going through one slit" and acting like a solid tiny ball of matter. I have variously referred to this above as "collapse" of the wave function -- in for instance "...once Alice is collapsed..." (and so on).

If one portion of Ψ is undergoing unitary evolution, then all of its parts must be so. If one portion of Ψ is in an eigenstate, then all parts of it must be so. This observation, (which is blindingly obvious on a chalkboard) is the entire prediction of Entanglement. The raw spatial distance between parts of Ψ makes absolutely no difference to this argument. translation--> The Alice and Bob photons could be separated by miles and it matters not. They could be separated by galactic distances and it matters not.
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Re: State of the Union

Postby Faradave on September 10th, 2018, 1:03 pm 

bangstrom wrote:an exchange of quantum information

There's a difference in information shared and information exchanged. If two people share a secret and one of them blabs (i.e. interacts with a third party), the information immediately changes state from secret to public, for both original people, regardless of their separation. Yet no information was exchanged between them.


The change in state is spacelike (instantaneous) if the two share the same inertial frame (the same spatial simultaneity). If they are in relative motion, they don't share a simultaneity and by some perspectives, the change in state will seem retroactive (note my avoidance of "retro-causal", since neither person interacted with the other).
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Re: Entanglement Theory Query

Postby mitchellmckain on September 10th, 2018, 3:07 pm 

hyksos » September 10th, 2018, 8:26 am wrote:
So what is happening in the Delayed-Choice Quantum Eraser experiment?

What is happening in the situation in which 100% of the photons reflect off the top glass? How did they "know" the mirror was down there, if they never went down there to interact with it? The answer is the photons don't "know" anything at all. . . but the Schroedinger wave does know there is a mirror. Because the Schroedinger Wave knows everything.

Ψ

Ψ not only knows where everything is right now, it also contains information about where everything will be in the future. Because Ψ is continuous (and "differentiable" if you prefer) it must necessarily carry information about the past as well.

I repeat my objection explained above that the term "delayed choice" is misleading. That is not how the experiment is conducted thus it shows no such thing as you claim here. The only choice here is in selecting which of the photons to look at and this says nothing at all about the wave knowing anything ahead of time. All it really establishes is the nonlocal behavior of the wave. Entanglement means you cannot treat them as independent agencies.


hyksos » September 10th, 2018, 8:26 am wrote:This is all very spook-bats to our common-sensical notions of materiality and physicality. But things like Entanglement and Delayed-Choice Erasers are clean, neat consequences of the orthodox formulation of Quantum Mechanics. This means there were men in Europe who knew about this as far back as 1929. YOu have to appreciate how vociferous Albert Einstein was in his rejection of QM.

To be a little more precise : Anyone who claims that the DCQE would not work as described (with retrocausality and that entails) then such a person would necessarily be suggesting that the collapse of Alice's photon causes a discontinuity in Ψ. There is no wiggle room. Either you agree that Alice's photon goes back into unitary evolution, or you necessarily are implying that Ψ has a discontinuity in it where her photon collapsed into an eigenstate. Thus DCQE is a "clean , neat" consequence of Ψ not containing mysterious discontinuities.

Even more precise "Unitary evolution" corresponds to the situation in which a measurement is not made, and a single photon acts according to wave mechanics, with all the requisite interference patterns. "Eigenstate" corresponds to the photon "going through one slit" and acting like a solid tiny ball of matter. I have variously referred to this above as "collapse" of the wave function -- in for instance "...once Alice is collapsed..." (and so on).

Discontinuity has always been an accepted fact of the quantum measurement problem and explaining that discontinuity is what the problem is all about.

But there is absolutely no need for retrocausality, for since decoherence is random there is no need to say at which detector decoherence occurs. And we have no reason to assume that which path the entangled particle takes is independent of what happens at the first detector. That is the real quantum weirdness -- challenging our assumption that all the parts are acting independently when in fact we know they do not.
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Re: Entanglement Theory Query

Postby davidm on September 10th, 2018, 4:52 pm 

Doesn't MWI do away with all this? No spooky action at a distance, no antirealism, no indeterminism, no wave function collapse, no alleged special role for consciousness?
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Re: Entanglement Theory Query

Postby davidm on September 10th, 2018, 5:02 pm 

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Re: Entanglement Theory Query

Postby mitchellmckain on September 10th, 2018, 6:49 pm 

davidm » September 10th, 2018, 3:52 pm wrote:Doesn't MWI do away with all this? No spooky action at a distance, no antirealism, no indeterminism, no wave function collapse, no alleged special role for consciousness?

Not really. It just changes where the non-locality comes in to how the elements of the superposition of the particle are associated with which elements of the superposition of the observer.


Just like with determinism, preserving locality in some imagined superposition which nobody can observe doesn't change the non-locality which is actually observed in what we really experience. Like I have said before, I can support the MWI only because there is more than one way of interpreting the non-observables. You can believe in a proliferation of worlds if you want, but there is no way to substantiate this. Meanwhile I can take this mathematics as simply reflecting the reality of future possibilities.
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Re: Entanglement Theory Query

Postby davidm on September 10th, 2018, 8:14 pm 

…preserving locality in some imagined superposition which nobody can observe doesn't change the non-locality which is actually observed in what we really experience.


But, Mitchell, isn’t this the point that Tipler, and others all the way back to Everett, have been making? “What we really experience,” under MWI, is just our limited perspective. MWI says there is no wavefunction collapse, and if there isn’t, nonlocality and indeterminism and antirealism simply vanish, since these things depend upon collapse.

Where, in Ψ, is there a wavefunction collapse? It doesn’t exist.
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Re: Entanglement Theory Query

Postby mitchellmckain on September 10th, 2018, 10:28 pm 

davidm » September 10th, 2018, 7:14 pm wrote:
…preserving locality in some imagined superposition which nobody can observe doesn't change the non-locality which is actually observed in what we really experience.


But, Mitchell, isn’t this the point that Tipler, and others all the way back to Everett, have been making? “What we really experience,” under MWI, is just our limited perspective. MWI says there is no wavefunction collapse, and if there isn’t, nonlocality and indeterminism and antirealism simply vanish, since these things depend upon collapse.


Sure but the only objectivity in science is what we can actually observe and measure NOT in ideas which can never be substantiated. Otherwise we might as well be talking about fairies, gods, and demons.

davidm » September 10th, 2018, 7:14 pm wrote:Where, in Ψ, is there a wavefunction collapse? It doesn’t exist.

The collapse is found when you try to connect this with what is actually measured and observed, which some people might give the label "reality." You can only say that it doesn't exist in the superposition which you are imagining which cannot be measured or substantiated in any way. It is like saying an infinite plane is a closed surface (what we call a projective plane) just because you can imagine a point at infinity. But the truth is that they are two different things. IF the superposition MWI posits really exist THEN there is no discontinuity. But like I said, that superposition isn't observable or measurable and is thus outside the objectivity of science.

Thus my understanding is different. Instead I see a fundamental discontinuity which defines both an arrow of time and distinguishes a point in space-time as the present. This frankly agrees far better with what we actually experience. Thus I see no reason whatsoever to credit the existence of this superpostion which, after all, we cannot observe and measure. This also probably explains why the Copenhagen Interpretation remains the majority opinion.
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Re: State of the Union

Postby bangstrom on September 11th, 2018, 2:50 am 

Faradave » September 10th, 2018, 12:03 pm wrote:
bangstrom wrote:an exchange of quantum information

There's a difference in information shared and information exchanged. If two people share a secret and one of them blabs (i.e. interacts with a third party), the information immediately changes state from secret to public, for both original people, regardless of their separation. Yet no information was exchanged between them.


The change in state is spacelike (instantaneous) if the two share the same inertial frame (the same spatial simultaneity). If they are in relative motion, they don't share a simultaneity and by some perspectives, the change in state will seem retroactive (note my avoidance of "retro-causal", since neither person interacted with the other).


How is this not strictly a matter of semantics? The change in identifying information from “secret” to “public” first happens only in the local of the one party and it has no immediate effect on the other party. There is no change on the opposite end unless there is a later exchange of information of the classical sort. Unless the person on the other end is clairvoyant.
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Re: Entanglement Theory Query

Postby bangstrom on September 11th, 2018, 3:20 am 

hyksos » September 10th, 2018, 8:26 am wrote:
The answer is the photons don't "know" anything at all. . . but the Schroedinger wave does know there is a mirror. Because the Schroedinger Wave knows everything.


If the Schroedinger wave can scout the path for the “know nothing” photon to follow, this makes the photon redundant to the explanation. We can dismiss with the photon as an imaginary phantom. This is no loss because the photon can’t be observed between source and sink by any means anyhow.
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Re: Entanglement Theory Query

Postby dandelion on September 11th, 2018, 5:06 am 

Does that suggest other formulations know stuff anthropically?
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Re: Entanglement Theory Query

Postby davidm on September 11th, 2018, 10:05 am 

Sure but the only objectivity in science is what we can actually observe and measure NOT in ideas which can never be substantiated.


It remains unclear whether MWI can be tested in principle or not. There have been proposals to test it. One involves a computer with a certain kind of reversible memory. I don’t recall the details, only that the computer envisaged is beyond our current technology. Paul Davies has argued that the double-slit experiment just is a test for MWI, demonstrating its existence. Once could also ask: is string theory science? As far as I am aware its claims cannot be tested even in principle.

Otherwise we might as well be talking about fairies, gods, and demons.


But MWI, whether true or not, can be derived from Ψ. Fairies, gods and demons are derived from nothing at all but the imagination.

Thus my understanding is different. Instead I see a fundamental discontinuity which defines both an arrow of time and distinguishes a point in space-time as the present. This frankly agrees far better with what we actually experience.


I don’t think personal experience is very compelling. In our personal experience, the earth seems to be flat, the sun seems to move across the sky, space and time appear to be absolute, and no superpositions are ever observed. Relativity theories also denies that there is any distinguished point in spacetime that is the objective present.

One must also asks: what causes the wavefunction collapse? That there is no agreement on this, seems to be scientifically problematic and may itself be a sign (not necessarily rising to the level of evidence) that it does not exist.

Science must also explain the Heisenberg cut, the alleged realm where the quantum yields to the classical. So far I see no science on this, either. Of course MWI dispenses with the cut as well as the collapse, and with all the other weirdness, and thus seems considerably more parsimonious than Copenhagen.
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Re: State Secret

Postby Faradave on September 11th, 2018, 11:22 am 

bangstrom wrote:How is this not strictly a matter of semantics?

In fact Quantum Mechanics depends on precise meanings (semantics), which differ from classical. What makes a secret a secret is privacy (what QM calls coherence). Two entangled particles share a quantum state, such as total-spin-zero. The secret of what spin they each have is so good, even the particles themselves don't know it. How do they achieve this? By not even having definite individual spin states. All that can be known is that the spins are opposite. A shared state is the ultimate secret!

bangstrom wrote:The change in identifying information from “secret” to “public” first happens only in the local of the one party and it has no immediate effect on the other party.

You're modifying "secret" to your own purposes. If I have a secret agent acting for me in a hostile country and he's found out, he could be killed off before I even know he's been discovered. Either way, I immediately have no secret agent (we're no longer an operational "team"). My secret is lost (globally) whether I know it or not. Yet I exchanged no information with that agent.


A shared spin state becomes two separate spin states once either is measured, without an exchange of information.
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Re: Entanglement Theory Query

Postby Braininvat on September 11th, 2018, 12:50 pm 

IIRC, there was an experimental test of MWI proposed in the 90s. Here it is...

https://arxiv.org/abs/quant-ph/9510007

The many-worlds interpretation of quantum mechanics predicts the formation of distinct parallel worlds as a result of a quantum mechanical measurement. Communication among these parallel worlds would experimentally rule out alternatives to this interpretation. A procedure for "interworld'' exchange of information and energy, using only state of the art quantum optical equipment, is described. A single ion is isolated from its environment in an ion trap. Then a quantum mechanical measurement with two discrete outcomes is performed on another system, resulting in the formation of two parallel worlds. Depending on the outcome of this measurement the ion is excited from only one of the parallel worlds before the ion decoheres through its interaction with the environment. A detection of this excitation in the other parallel world is direct evidence for the many-worlds interpretation. This method could have important practical applications in physics and beyond.

Comments: 17 pages, standard LaTex, no pictures, comments welcome, revised version corrects typing error in mixing time
Subjects: Quantum Physics (quant-ph)
Journal reference: Found.Phys.27:559,1997
DOI: 10.1007/BF02550677
Cite as: arXiv:quant-ph/9510007
(or arXiv:quant-ph/9510007v3 for this version)


It is testing what's called a weak coupling theory (e.g. gravity as the coupler).
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Re: Entanglement Theory Query

Postby mitchellmckain on September 11th, 2018, 1:14 pm 

davidm » September 11th, 2018, 9:05 am wrote:It remains unclear whether MWI can be tested in principle or not. There have been proposals to test it. One involves a computer with a certain kind of reversible memory. I don’t recall the details, only that the computer envisaged is beyond our current technology. Paul Davies has argued that the double-slit experiment just is a test for MWI, demonstrating its existence. Once could also ask: is string theory science? As far as I am aware its claims cannot be tested even in principle.

Yes, there are a VERY few who imagine that MWI is a theory rather than an interpretation but I have looked at these proposed tests and I think they are not only not only just as imaginary as this proposed superposition but ultimately inconsistent with MWI itself.

davidm » September 11th, 2018, 9:05 am wrote:
Otherwise we might as well be talking about fairies, gods, and demons.


But MWI, whether true or not, can be derived from Ψ. Fairies, gods and demons are derived from nothing at all but the imagination.

Oh... I have seen people deriving these things from just about anything... math... science... observations... you name it. None of it makes any sense to me, to be sure. The point is that the objectivity of science doesn't come from such derivation but from actual measurements and observation in written procedures which anyone can perform to get the same results.

davidm » September 11th, 2018, 9:05 am wrote:
Thus my understanding is different. Instead I see a fundamental discontinuity which defines both an arrow of time and distinguishes a point in space-time as the present. This frankly agrees far better with what we actually experience.


I don’t think personal experience is very compelling. In our personal experience, the earth seems to be flat, the sun seems to move across the sky, space and time appear to be absolute, and no superpositions are ever observed. Relativity theories also denies that there is any distinguished point in spacetime that is the objective present.

Once we leave the objective methodology of science, personal experience is all we have.

davidm » September 11th, 2018, 9:05 am wrote:One must also asks: what causes the wavefunction collapse? That there is no agreement on this, seems to be scientifically problematic and may itself be a sign (not necessarily rising to the level of evidence) that it does not exist.

Science must also explain the Heisenberg cut, the alleged realm where the quantum yields to the classical. So far I see no science on this, either. Of course MWI dispenses with the cut as well as the collapse, and with all the other weirdness, and thus seems considerably more parsimonious than Copenhagen.

There is no agreement on the measurement problem, just as there is no agreement on the MWI. But I do think there is more of a consensus that it is not human consciousness as is effectively the case in the MWI, but rather in what measuring devices do (such as amplification and entangling the behavior of more and more particles).
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Re: Entanglement Theory Query

Postby bangstrom on September 11th, 2018, 4:34 pm 

dandelion » September 11th, 2018, 4:06 am wrote:Does that suggest other formulations know stuff anthropically?


Particles can, at times, interact non-locally as if space and time between them did not exist. This makes them appear to us as being sentient with a “knowledge” of their environment. This does not mean particles are knowledgeable but it means we have an incomplete view of causality.
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Re: State Secret

Postby bangstrom on September 11th, 2018, 4:39 pm 

Faradave » September 11th, 2018, 10:22 am wrote:
bangstrom wrote:How is this not strictly a matter of semantics?

In fact Quantum Mechanics depends on precise meanings (semantics), which differ from classical.


Quantum “information” is an acceptable term in QM and has been for decades. Quantum information is the thing that informs particles of their quantum “identities.” There is a recognized difference between quantum information and classical information. The former is non-local and the latter is local but I see no reason to change the nomenclature since the similarities outweigh the differences.
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Re: Entanglement Theory Query

Postby dandelion on September 12th, 2018, 6:52 am 

Thanks, Bangstrom, I wasn’t addressing you specifically, sorry, but I'm interested more generally in the thread about physical interpretation following computation rather closely. The question follows a bit from another thread with Carroll, entanglement and Hilbert Space, and was about some clarification of an extent of this which might even have an anthropic nature or else some personification in the language as you’ve replied about, thanks, and about whether such closeness would follow also say equivalent matrix mechanisms. Maybe some mention of continuity in another discussion here might indicate some preferences about that. Regarding info, btw, I prefer views agreeing with exchange of information between two interacting physical systems and not agreeing with Faradave’s objections.
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Re: Dys-connected

Postby Faradave on September 12th, 2018, 10:47 am 

bangstrom wrote:the former [quantum entanglement] is non-local

In ER=EPR, spacelike wormholes which provide an equivalent description of entanglement indeed represent a non-local connection. But these are specifically non-traversable wormholes. The connection provides a reference about which properties (e.g. spin) of the entangled particles may correlate but forbids communication or translation of any sort, including information. "Superluminal signaling" is specifically excluded.
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Re: Dys-connected

Postby bangstrom on September 12th, 2018, 12:20 pm 

Faradave » September 12th, 2018, 9:47 am wrote:
bangstrom wrote:the former [quantum entanglement] is non-local

In ER=EPR, spacelike wormholes which provide an equivalent description of entanglement indeed represent a non-local connection. But these are specifically non-traversable wormholes. The connection provides a reference about which properties (e.g. spin) of the entangled particles may correlate but forbids communication or translation of any sort, including information. "Superluminal signaling" is specifically excluded.


I can agree with all that except for the exclusion of a communication of information. Entanglement has a definite appearance of information sent and information received which is necessary for a correlation of of quantum identities.
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Postby davidm on September 12th, 2018, 12:47 pm 

I should correct something I wrote above. It was not Paul Davies who argued that the two-slit experiment is a test that demonstrates the multiverse, but David Deutsch, in his book "The Fabric of Reality." Deutsch says Many Worlds falls out of the experiment in the same way that dinosaurs fall out of dinosaur fossils and footprints.
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Re: Entanglement Theory Query

Postby JustAsking on September 12th, 2018, 1:45 pm 

bangstrom » September 11th, 2018, 3:34 pm wrote:
dandelion » September 11th, 2018, 4:06 am wrote:Does that suggest other formulations know stuff anthropically?


Particles can, at times, interact non-locally as if space and time between them did not exist. This makes them appear to us as being sentient with a “knowledge” of their environment. This does not mean particles are knowledgeable but it means we have an incomplete view of causality.
Sorry to barge into this thread. But this comment you made reminds me of an idea I've had for a long time. I'm just an informed layman. But I thought I'd mention my idea and see what you guys thought.

In every discussion of entangled particles the assumption is that there are two particles. But I remember from reading Flatland years ago that for example a 3D torus passing through a 2D "world" would appear as a single circle eventually becoming two circles, even though there's really only one torus. Could the same basic idea apply with entangled particles? There aren't two particles, there's only one, in a higher dimension. Of course we only observe the particles in 3D, and so posit exchanges of info and whatnot. Well there is no exchange of info or any actual entanglement I suppose since it's just the same single 4D particle appearing to us to be in two different 3D places.

Thoughts?
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Re: Getting Physical

Postby Faradave on September 12th, 2018, 3:17 pm 

bangstrom wrote:I can agree with all that except for the exclusion of a communication of information.

dandelion wrote:I prefer views agreeing with exchange of information

Information has no existence apart form the physical. It is always expressed in terms of mass-energy thus, restricted by universal speed limit c.

It's fine to consider an entanglement to represent one state of information and disentanglement to be another form. But change in state is not the same as communication, even if it appears to have been coordinated.

In a similar sense, the universe imposes the same physical laws throughout space and time (that's what makes them laws) but that universal coordination of observed laws in no way requires the coordinated objects to communicate with each other faster than c.

JustAsking wrote:Could the same basic idea apply with entangled particles? There aren't two particles, there's only one, in a higher dimension.

Hi JA,
The shared state is considered "one" and can be modeled in 4D but the particles have separate spatial locations. One of the pair can annihilate or drop into a blackhole without the other (of course breaking the entanglement), so in most respects they meet the same typical properties of individual particles.
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