Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: jeffreyH on 16/08/2015 16:49:14
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Until I realised exactly what quantum teleportation was I followed Einstein's view on spooky action at a distance. In my own opinion Einstein cannot be right. There actually is spooky action at a distance. I would appreciate other viewpoints.
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Until I realised exactly what quantum teleportation was I followed Einstein's view on spooky action at a distance. In my own opinion Einstein cannot be right. There actually is spooky action at a distance. I would appreciate other viewpoints.
Typically I would love to discuss an interesting subject such as this. However after looking at the Wikipedia article on the subject at:
https://en.wikipedia.org/wiki/Quantum_teleportation
it appears to require a background understanding of quantum computing and perhaps classical and/ or quantum information (qubits etc.) and that's something I haven't gotten around to learning as of yet. Sorry. But I'll be watching this thread with great interest. I might not know the subject but I might be able to see when someone's trying to bs you.
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Until I realised exactly what quantum teleportation was I followed Einstein's view on spooky action at a distance. In my own opinion Einstein cannot be right. There actually is spooky action at a distance. I would appreciate other viewpoints.
I think it depends what you (and Einstein) mean by 'action'; as it stands, entanglement involves no instantaneous transfer of information, and whether any transfer actually occurs depends on your preferred interpretation of QM (e.g. Everettian 'Many Worlds' doesn't require it) - although you may find some interpretations less palatable than the idea of instantaneous transfer.
In any case, quantum teleportation uses classical (non-instantaneous) information transfer; as I understand it (poorly) the quantum entanglement is involved in establishing the quantum state of the particle to be teleported, not in transferring it.
There is also the philosophical problem of identity - techniques like this are destructively transferring the quantum state information of one particle, and imparting it to another particle. This state transfer doesn't intuitively seem like a particle teleportation, but particles (of a type) are only identifiable (distinguishable) in terms of their quantum state, so quantum state identifies the particle, so, for all intents and purposes, the particle actually has been teleported.
This is reminiscent of the Star Trek Transporter problem - if it destructively scans you and sends the information that will allow an atomically identical replica of you to be constructed in a remote location, is that really 'you' at the destination? or do you die and get replaced by a clone that thinks it's you? It seems that the essence of 'you' is not material, but a pattern - in much the same way as Conway's Game of Life (https://en.wikipedia.org/wiki/Conway%27s_Game_of_Life) is only interesting given a specific pattern of cell states; or quantum teleportation of a particle via state transfer. But would you step into a Star Trek Transporter (assuming it was 100% reliable) ?
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Quantum teleportation, or action-at-a-distance, is the current interpretation of the appearance of entanglement. When two objects are entangled, the state of one is linked to that of the other... if one has a spin "up", for example, the other might be required to have a spin "down". This is true even if the particles' states are unobserved and indeterminate and each particle has a state of 1/2 "up" and 1/2 "down". The fact that the unobserved states are really a combination of both (mutually exclusive) states and not some definite values that are merely unobserved (called hidden variables) was proven in an experiment designed by John Bell... Bell's Inequality. But, when one observes the state of one particle, one finds simultaneously what the state of the other particle will be observed to be... even if the other particle is very far away.
The interpretation most common in quantum mechanics (and not accepted by Einstein) is that the act of observation instantly changes the state of the universe across whatever distance separates the particles.
There are problems with this. Not only does it require information to travel faster than c, the speed of light, but the communication must be instantaneous. There cannot be any intervening time. While exceeding the speed limit c would be problematical, it could be dealt with. The problem with instantaneous communication is that it doesn't have any physical meaning. Not only the rate of time's passage differs for observers in different reference frames, the sequence of events isn't guaranteed to be the same (unless they are causally linked like a series of dominoes knocking each other down in sequence). In a real physical universe where spacetime isn't really flat anywhere and pretty much everything is moving relative to other things, there cannot be any uniquely identifiable time assigned to any two events.
Basically, Einstein proved "non-simultaneity"... there cannot be any way to define two events as simultaneous except for observers sharing a reference frame. Two physically separate events, (A) & (B), could be simultaneous from the perspective of one observer while from another observer's (equally valid) perspective, (A) will precede (B), and for a third perspective, (B) will precede (A).
Action-at-a-distance requires that Relativity be wrong in some very fundamental way.
Another problem is the idea that an observation alters the universe. In my opinion, that's silly on the face of it. Observation alters the observer.
An alternative interpretation for the observed consequences of entanglement is that, by altering the state of the observer, the set of possible observations the observer can make is altered. This, however, requires that we exist in a multiverse in which all possibilities "exist", potentially, and that it's only the state of the observer that constrains what can actually be observed. Since this is entirely consistent with Bell's experiment's results, this seems like a more reasonable interpretation.
Quantum mechanics has shown that, until an observation is made, every allowable state coexists for the system in question. Once the observation is made, the quantum state of the observing system becomes entangled with one specific state and any contrary observation is then disallowed by the rules of quantum mechanics.
Any system (including any observer) can be described by a quantum state matrix of eigenvalues. When the known physical laws are satisfied, the system can be described by a matrix that’s balanced about the main diagonal, a Hermitian matrix. If a system were to interact with even one quantum that violates the rules, the resulting matrix will be non-Hermitian. Schrödinger described such systems as, “unobservable.” I presume that only observers with Hermitian state matrices are allowed, so no observer could ever make an observation that violated the rules (in this case, the entangled states).
I think of this as Schrödinger’s Filter. It provides a “local” (slower than light) explanation for the appearance of action-at-a-distance. It also eliminates the non-causal nature of quantum mechanics.
Tossing in another idea of mine… all models of causal systems, like our physical universe, break down at time = zero, where they require an effect without a prior cause. So, what if the “prior” condition was non-causal. Difficult to imagine but one can at least identify some characteristics it would not have… there would be no conservation laws, no space, no time, no restrictions on “something” turning into “nothing” or vice-versa. I hypothesize that such a condition might possess boundless information. If Schrödinger’s Filter is correct, then it’s all that’s necessary to extract every possible observation by every possible observer in every possible causally-consistent universe from this pre-time = zero Chaos. From a non-causal background state, a complete multiverse would spontaneously occur and every possible observation by every possible observer would “find itself.”
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This is very fundamental. I appreciate the responses. Very thought provoking. Especially concerning Hermitian matrices, Bell's inequality and the Schrödinger filter. I do not personally believe that there is something fundamentally wrong with relativity. I think we may be looking at entanglement in the wrong way. At the moment I am considering some ideas on this matter. It may be a while before I have time to formulate anything concrete.
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... Not only does it require information to travel faster than c, the speed of light, but the communication must be instantaneous.
Entanglement doesn't require classical information transfer FTL, as the state of both particles is uncertain until measured. Entlanglement superposition behaves as if there are two 'virtual' pairs of complementary particles, and measuring the state of one particle determines which pair you're dealing with.
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I agree with Einstein's opinion that non-local effects, action-at-a-distance, AAAD, isn't possible. The reasoning is simple, really. Special Relativity, SR, depends on two things being true:
1) The speed of light is the same for all observers (measured from any reference frame)
2) The laws of physics are the same for all observers (i.e. the same everywhere, always)
For Special Relativity to be wrong, one of those assumptions must be wrong.
An unavoidable consequence of SR is that there is no prefered frame of reference. There is no place that's special and no time that's special. For any two events, (A) & (B), separated in space, there must exist three categories of reference frames:
1) Frames for which (A) precedes (B)
2) Frames for which (A) & (B) are simultaneous
3) Frames for which (B) precedes (A)
Also, all three categories of observations are equally valid.
For this reason, an inescapable conclusion of Relativity is "non-simultaneity"... there is no such thing as two physically separate events being simultaneous. For every frame of reference for which the events are simultaneous there will be other, equally valid frames for which they are not. Whether two events are simultaneous is entirely relative to one's frame of reference WRT the events.
The problem with AAAD is that the effect of observing the state of one member of an entangled set must alter the state of its partner instantly. Not just faster than light. Instantly.
This, however, requires that one frame of reference be special. AAAD requires that there can only be one “real” observer for any event in the whole universe. Let me explain...
Consider Schrödinger’s Cat. Suppose the experiment is done in a specially designed laboratory, enclosed by a Schrödinger-catbox-quality wall. The lab, when sealed, is information-proof. Within the lab, the experiment is performed. After some pre-arranged time, outside the lab, everyone knows the experiment has been completed. Yet, for them, the cat and the scientists that have observed it, exist in an indeterminate state. So, are the observations of the scientists within the lab insufficient to collapse the wavefunction? To them, their experiences will seem real. When the lab is opened and the rest of the world can learn the results, is that when the experimenters assume a definite state, including their memories? That is when the cat’s state becomes real for the external observers.
Not only does the AAAD interpretation of entanglement require that Special Relativity be entirely wrong, but it's not consistent with itself... the first observer should collapse the wavefunction but this extended Schrödinger's Cat experiment shows that interpretation doesn't work, either.
Basically, we know that Special Relativity is correct. Therefore we know that simultaneity has no physical meaning (except to individual observers).
Whatever the correct interpretation of entanglement is, we can know for certainty that it doesn't depend upon the luminiferous ether, phlogiston, action-at-a-distance, fairies at the bottom of the garden, or any other non-existent factors. Any valid model will depend ONLY on things that are physically possible.
To me, the logical explanation is that observation doesn't alter the universe, everywhere, instantly. Observation alters the observer.
A multiverse interpretation allows for a purely causal and local interpretation for all quantum "weirdness". Unfortunately, while it is consistent with all observations and eliminates most incompatibilities between Relativity and Quantum Mechanics, it's not sufficiently aesthetically appealing for physicists to seriously consider (unlike String Theory which had no logical foundation but is mathematically beautiful and so has been able to divert physics for many years).