|
|
|
|
|
| Quantum Entanglement and Locality
Posted: 6/22/2009 4:59:32 AM | I gather that one of the predictions of Quantum Theory is that particles can have "quantum entanglement", that they can be linked over great distances, and that if we separate them, and then observe some property in one, the corresponding property will automatically occur in the other, even though there is no way for them to communicate.
However, I also gather that Einstein pointed out that the laws of the Universe act with "locality", that seems to me to be, that they only act based on what is near (local) to them.
So at first glance, there is a conflict: does the universe follow locality or non-locality?
In reading an article, I noticed something, that each particle is capable of having multiple simultaneous states and even locations, as predicted by the wave function, and that only when those particles are observed or measured, in that something interacts with them, that at that point, the wave function collapses, and that is when they have a single state or location. It occurred to me, that things are more likely to interact with something closer to them. Therefore, it might be true to say that wave function collapse is going to be far more likely to be the result of an interaction with a local phenomena, and not a distant one.
Therefore, I suggest that it might be that the universe can be non-local as much as localised. It is just that the vast majority of phenomena would be localised, by raised probability of interactions.
This might explain why the inverse square law occurs so often in the laws of physics. The inverse square law is just how probable it would be for a particle to interact, because the closer the distance between particles, the more easy it would be for interaction to occur between them. The result of many many such interactions would mean the expected value of the forces involved might compute to be proportional to the inverse square law.
This might even explain how gravity works in quantum theory, as then, gravity would be the action of not a single graviton, but billions of gravitons all interacting together, which by the laws of probability, would raise the expected amount of force involved to be proportional to the distance between them.
Think of a those swinging balls on strings that are often in a doctor's office. Now, imagine that on each side, you put 2 big balls. Then the first big ball would interact with the smallest ball next to it, which would interact with the next one along, and the next, until it interacts with the one on the end, which would then be given its own momentum and would interact with the balls in between and give its own effect on the first big ball. Consider then if you had not just a few balls in a straight line, but billions of them all around, not just between the balls, but on either side, and on all the other sides of the big balls. Then the balls would interact. But there would be more force passing between them, because the forces would be greater when they can be passed by less balls. More balls between them would mean that the gravitational forces would be absorbed in greater part by the gravitons.
Moreoever, this might even be in line with Einsteinian gravity, if we suppose that the gravitons are part of what makes space space. If the gravitons are not quite particles in their own right, but are a necessary part of what makes space, then the force of gravity passes between particles via space itself, and the greater the distance between them, the more space there is, and the more that space itself absorbs the forces involved, thus lowering the force of gravity with greater distance.
Going further, this might even explain the existence of Dark Matter, as dark matter might be some component of those gravitons themselves, but are invisible, because they affect photons, and so don't really absorb them, making them invisible to light.
I know all this is supposition. So I have no true expectation that any of it is right. But it was an idea, and I just thought it might shed some possible light on the issue. What do you all think? Do you think it has some merit? | |
|
| Quantum Entanglement and Locality
Posted: 6/22/2009 5:31:15 AM | It's also possible that what we perceive as space and distance are in fact an illusion.
There is no space between anything and all things are connected.
The Universe is only a single photon going nowhere. | |
|
| |
| Quantum Entanglement and Locality
Posted: 6/22/2009 8:57:18 AM | | The prevalence of inverse-square laws is easily explained by geometry. The strength of a force originating at the center of a sphere is inversely proporional to the surface area, which varies as the square of the radius. Nothing more profound is required. | |
|
| Quantum Entanglement and Locality
Posted: 6/22/2009 10:31:10 AM | Scientists have demonstrated that it is possible to effectively 'teleport,' or transmit the information innate to one particle, into another particle at a different location under vacuum. It's not quantum entanglement per se, but it does suggest that the inverse square rule has its exceptions - what's really exciting, is that if we manage to work this whole quantum entanglement business out, we'll have access to faster-than-light communication.
Imagine being able to send a probe out into space, and receive immediate telemetry from it, in real-time, by virtue of a paired entanglement router containing one half of the entangled particles aboard the probe, and the remainder on the ground. The probe receives data, pushes it into the entanglement router, causing the associated particles back on earth to spit them back out instantly, regardless of distance. | |
|
| Quantum Entanglement and Locality
Posted: 6/22/2009 11:18:34 AM | There was a demonstration of quantum entanglement through projecting tiny images about 6 or 7 months ago. The problem with entanglement is that it has to happen when the particle is created (for lack of a better word), both have to be created at the same time and under specific conditions for the process to take hold.
The system hellgremlin describes was an idea I used for one of my sci-fi stories. You have a compute which is attached to a tank. Inside that tank are particles which have an entangled partner aboard some distant ship, station, or other facility that couldn't be attached to the communications grid. The particles are sorted by heavy to light, heavy falls down, while light tends to float; so important places like emergency response, government, and military could be given heavy particles , while less important things like civilian transport would be given lighter particles.
One thing I've always wondered about is whether you could use a sort of entangled gateway to move stuff from one place to another without the whole break it down rebuild it process that quantum transportation describes. | |
|
| Quantum Entanglement and Locality
Posted: 6/22/2009 11:41:25 AM | | The information stored in a particle has to be stored somehow before it appears elsewhere. Easy with one particle, not so much with a near-infinite number. At least, that's my understanding... which is at best, rudimentary. | |
|
| Quantum Entanglement and Locality
Posted: 6/22/2009 12:57:34 PM |
Quantum mechanics is a local theory. Look up Bell's inequality and the epr experiment.
As I understand it, QM violates Bell's inequalities, showing that the EPR trio, Bell and Bohm were wrong (i.e. you cannot explain QM in terms of local hidden variables). If by a local theory physicists mean influence is restricted to within the light cone, then QM violates this requirement. | |
|
| Quantum Entanglement and Locality
Posted: 6/22/2009 1:05:42 PM | Wow, that could be the most intelligent post I've seen from you. It is always nice to see people actually thinking.
A couple of observations:
<div class="quote">
Moreover, this might even be in line with Einsteinian gravity, if we suppose that the gravitons are part of what makes space space. If the gravitons are not quite particles in their own right, but are a necessary part of what makes space, then the force of gravity passes between particles via space itself, and the greater the distance between them, the more space there is, and the more that space itself absorbs the forces involved, thus lowering the force of gravity with greater distance.
As you might recall from an earlier discussion undertaken with reference to Kant, the concept of "space" tends to be one which we humans intuit as applicable to the essence of our understanding of reality. Hume agrees upon this point, and further expresses his opinion that our 'categorical concept' of spatiality is informed by just two of our senses: sight, and touch.
However, it is currently a goal of some who are of a philosophic mind to explore the implications of what might be called a "transcendental empiricism" (to use a term favoured by Gilles Deleuze); and in asking what it is of experience which is not localizable to the perceiver, one must consider how such a 'categorical concept of space' might be composed strictly from an understanding of those events and objects, the occurrence of which define what spatiality in fact is.
Taking this approach, the idea that 'space' is defining the "particles" of which you speak becomes problematic; which is not to say that anyone here is right or wrong but only that there are other conceptual alternatives which as of yet remain unexplored.
<div class="quote">
Going further, this might even explain the existence of Dark Matter, as dark matter might be some component of those gravitons themselves, but are invisible, because they affect photons, and so don't really absorb them, making them invisible to light.
Again, to look at this from a different perspective, it may also be the case that different gravity wells affect sub-atomic cohesion differently than we experience and observe the case to be in our particular solar gravity well; an effect which might be termed 'quantum gravity'. So our inability to view Dark Matter could simply be due to differences in electron shell potentials between atoms formed in vastly different gravity wells - in which case, there just isn't anything in our solar system which could interact directly with photos emitted by "Dark Matter".
What becomes of the concept of entanglement then? Is it perhaps in really something quite mundane, like the ability of two atoms formed within comparable gravity wells to interact through photons that either is capable of emitting and absorbing? Is that a mathematical rarity, something seemingly exotic in definition through equations, simply because of the statistical rarity in this universe of the kinds of matter we are familiar with? Because once the equations are balanced and checked and confirmed, sense still has to be made of what is being referred to; and it isn’t difficult for the most abstract and exotic explanations to be visited upon what is at heart the obvious and commonplace within out own ever expanding experience. | |
|
| Quantum Entanglement and Locality
Posted: 6/22/2009 1:14:00 PM | What becomes of the concept of entanglement then? Is it perhaps in really something quite mundane, like the ability of two atoms formed within comparable gravity wells to interact through photons that either is capable of emitting and absorbing?
I've always understood quantum entanglement to mean two particles possessing the same information across a spatial divide. Not identical information, the same information - effectively, the particle exists in two places at once, and both counterparts react in tandem to stimuli directed against one of its "halves".
I could be totally wrong. | |
|
| Quantum Entanglement and Locality
Posted: 6/22/2009 6:21:06 PM | | So could we all... I mean, how could that even be tested for, if the process of observing influences the particles being observed? Just establishing that the particles were in different locations would preclude determining what information they express, would it not? | |
|
| Quantum Entanglement and Locality
Posted: 6/22/2009 6:29:30 PM | Ah yes, good old Heisenberg, bane of Star Trek teleporters. As I understand it (which I likely don't,) the only way to observe a particle with current technology, is to bash another particle into it, and see where it flies or what it breaks apart into, so to speak.
I wonder if there may be indirect methods of observing particles. Perhaps via extrapolation of their effect on neighbouring particles, perhaps by paying attention to the empty space between them, their mass... hell if I know.
Sure is fun to think about, though. | |
|
| Quantum Entanglement and Locality
Posted: 6/22/2009 10:14:01 PM | As I understand it, QM violates Bell's inequalities, showing that the EPR trio, Bell and Bohm were wrong (i.e. you cannot explain QM in terms of local hidden variables).
That's ``hidden variables,'' not ``local hidden variables.'' Hidden variables are anything but local.
If by a local theory physicists mean influence is restricted to within the light cone, then QM violates this requirement.
Incorrect. The causality restriction to events inside the light cone is built in explicitly. If you think quantum mechanics involves faster than light influences, you are confusing causation with correlation. | |
|
| Quantum Entanglement and Locality
Posted: 6/22/2009 10:18:03 PM |
Scientists have demonstrated that it is possible to effectively 'teleport,' or transmit the information innate to one particle, into another particle at a different location under vacuum.
The particles in question were photons and it wasn't the information that was teleported. It was the photon itself. The so-called ``no-cloning theorem'' shows that it is impossible to copy a quantum state, so the only possibility is that the actual photon is teleported. | |
|
| Quantum Entanglement and Locality
Posted: 6/23/2009 1:43:34 AM |
If you think quantum mechanics involves faster than light influences, you are confusing causation with correlation.
I'm thinking of an experiment done in France (Aspect, Dalibar and Roger) and others, whereby secondary filters are switched fast enough such that influence between entangled photons hasn't had time to travel between them, yet they still violate Bell's inequality. | |
|
| Quantum Entanglement and Locality
Posted: 6/23/2009 3:08:47 AM | RE Msg: 14 by abelian:
Scientists have demonstrated that it is possible to effectively 'teleport,' or transmit the information innate to one particle, into another particle at a different location under vacuum. The particles in question were photons and it wasn't the information that was teleported. It was the photon itself. The so-called ``no-cloning theorem'' shows that it is impossible to copy a quantum state, so the only possibility is that the actual photon is teleported. | |
|
| Quantum Entanglement and Locality
Posted: 6/23/2009 8:47:59 AM | Not possible Either. Information Theory 101: if you clone a hard drive, by copying it identically, right down to its electrical states, you clone its contents, and you've copied ALL the data.
Go read something about quantum mechanics so you have an idea of how a quantum state differs from a hard drive. Alternatively, do a search on google for ``no cloning theorem.'' If, after you understand what it means, you find an error, do not post it here until after you submit an article to phys rev lett. This is not the place to publish something of that much interest to physicists everywhere. It's also essential for quantum cryptography, so your ``proof'' that the theorem is wrong has very widespread interest.
So either the experiment must be wrong, or the "theorem" is wrong, or the theorem is misunderstood,
The editors at phys rev will be happy to send an article on the subject to referees who give your argument careful consideration if it contains the mathematics necessary to prove that. | |
|
| Quantum Entanglement and Locality
Posted: 6/23/2009 8:54:19 AM | | Well, the Aspect experiment is well known, but that doesn't support anything you've said beyond violating Bell's inequality. It's also well known that nothing about entanglement involves the propagation of anything at superluminal velocities. You are confusing correlation with causation. | |
|
| |
| Quantum Entanglement and Locality
Posted: 6/23/2009 9:30:05 AM | | Entanglement happens as I understand it by every particle that makes up an object (particle used loosely to describe even the subatomic), being bound to the same state. They have the same data upon creation so they react the same, starts a big long chain of cause-effect except the cause can be at one of them while the effect can manifest at both of them. There's doesn't need to be a transfer between the two of them because deep down they are reacting to a hard set of functions, and then they had the same data to start with they will both reach the same conclusions and then act on those conclusions, hence why they must be created in pairs. I guess that isn't as clear as I wanted it to be, I just barely grasp the concept myself. | |
|
| Quantum Entanglement and Locality
Posted: 6/23/2009 10:04:23 AM | | Entanglement occurs when a system of particles can be described by a single state vector. In other words, unlike classical mechanics (which, however is a limiting case of quantum mchanics), a quantum state is inseparable. For example, electrons can have two polarization states with spin = 1/2. Call them |+1/2> and |-1/2>. Call the polarization direction x. Two electrons produced by a coherent process are a single quantum state. Either a triplet with spin = 1 or a singlet with spin = 0, not two individual electrons. That state cannot be separated into the individual electrons which make it up. | |
|
| Quantum Entanglement and Locality
Posted: 6/23/2009 10:40:06 AM |
Well, the Aspect experiment is well known, but that doesn't support anything you've said beyond violating Bell's inequality. It's also well known that nothing about entanglement involves the propagation of anything at superluminal velocities. You are confusing correlation with causation.
Aspect's experiment, as I understand it, shows that the violation of Bell's Inequalities cannot be explained by some light speed signal between the two detectors, or influence between the particles in question travelling from one to the other as they hit the detectors. If this is the case then presumably you explain their behavior by specifying extra information that is missing or inaccessible when the particles are created, i.e. they already have a `plan' (know what each will do at the detector). But this cannot be the case, because the inequalities are violated (which I think is the point of the violation of Bell's Inequalities).
It's clear from the nature of entanglement that you cannot have both the principle of locality and Realism (in the spirit of classical mechanics - i.e. special relativity). Something has to give! | |
|
| Quantum Entanglement and Locality
Posted: 6/23/2009 11:26:55 AM | RE Msg: 17 by abelian:
Go read something about quantum mechanics so you have an idea of how a quantum state differs from a hard drive. Can you suggest an example of something that demonstrates the difference?
Alternatively, do a search on google for ``no cloning theorem.'' Did that. Wikipedia has the proof. But it assumes that you know Dirac notation and the appropriate laws. Right now, it's a bit confusing for me.
If, after you understand what it means, you find an error, do not post it here until after you submit an article to phys rev lett. Not up to you, until you buy the site from Markus.
This is not the place to publish something of that much interest to physicists everywhere. I really don't have the confidence yet to make myself that famous for something I've proved. Mostly, it's just a hobby for me to prove stuff that has never been proved before.
It's also essential for quantum cryptography, so your ``proof'' that the theorem is wrong has very widespread interest. There is a misnomer in cryptography. Many people think that cryptography represents perfectly secure information, by relying on an algorithm that can only be resolved in one direction, because they are based on a mathematical puzzle that cannot be solved. In reality, both directions exist. It is just that with current knowledge, only one method is known, because no-one has yet figured out how to solve the mathematical puzzle. That's how the current public-key private-key cryptography systems came to be used, because the previous methods were "cracked", in that the mathematical puzzle that it was based on, was solved, and thus the algorithm to convert the public key to the private key became known as a result. Quantum cryptography relies upon the same assumption, that right now, quantum information is stored in objects, based on the formulas of quantum physics, that represent a type of mathematical puzzle that cannot be solved. In reality, it is merely that no-one has figured out how to solve it yet. Once someone does figure out how to reverse the mathematical formulae that are the basis of quantum theory, then the puzzle becomes solved, and the algorithm becomes known as well.
So either the experiment must be wrong, or the "theorem" is wrong, or the theorem is misunderstood, The editors at phys rev will be happy to send an article on the subject to referees who give your argument careful consideration if it contains the mathematics necessary to prove that.
I really think I need a basic primer on QM, for those who have a degree in maths, but haven't been taught it.
Anyway, I merely pointed out the basic logical consequences of the "no-cloning theorem". If you clone the object, you clone its information as well. If the "no-cloning theorem" holds absolutely, then you cannot clone the object either, and you cannot have a copy of the object whose information can be reversed by finite multiple steps of simple reversible transformations, because then you could work out the information from the transformed copy. In other words, you could not have quantum entanglement, not unless those objects are completely different, except in one particular attribute that could be reversed in the second entangled body, and only if the "no-cloning theorem" would allow for those particular transformations, but no other, and then the theorem is not absolute. | |
|
| Quantum Entanglement and Locality
Posted: 6/23/2009 12:09:15 PM | Aspect's experiment, as I understand it, shows that the violation of Bell's Inequalities cannot be explained by some light speed signal between the two detectors,
Of course not, because no such signal is required. How many times do I have to say you don't know the difference between correlation and causation before you stop trying to base an argument on confusing those two things?
It's clear from the nature of entanglement that you cannot have both the principle of locality and Realism (in the spirit of classical mechanics - i.e. special relativity). Something has to give!
In this case it was Einstein'd notion of realism. However, since that notion of realism conflicts with lots of other quantum mechanics, giving it up is not really too controversial.
| |
|
| Quantum Entanglement and Locality
Posted: 6/23/2009 12:32:01 PM |
Not up to you, until you buy the site from Markus.
Sorry, I was thinking more along the lines that if you had discovered something so profound, you would naturally want to publish it in a physics journal before posting it in a pof forum. I'm not trying to stop you from publishing here first, but if it were me, I'd be in too much of a hurry to get it to prl to hink about posting here. But, suit yourself.
There is a misnomer in cryptography. Many people think that cryptography represents perfectly secure information, by relying on an algorithm that can only be resolved in one direction, because they are based on a mathematical puzzle that cannot be solved. In reality, both directions exist.
You are confused. Quantum cryptography relies on the physics of quantum mechanics. In particular, the impossibility of intercepting a photon and cloning the original state. At the moment, it's impractical for anything but key distribution. For further information, you will find C. Bennett to be a great source.
As a quick refreser of what quantum information means before you object by throwing out the jargon again, the definition comes from von Neumann. S = -Tr (rho log (rho)) where rho is a density matrix and Tr designates the trace.
Basic Dirac notation. A state vector or ket |blah> is a ray in Hilbert space. A bra = delta_ij and the operator 1 is given by sum |blah> | |
|
|
|
Home
login 
