One thing is sure: there is NO superluminal transfer of information. This can be shown mathematically, in that the reduced density matrix of one system is unaffected by whatever measurement is done on the other system (or even whether a measurement is done).Ron Smith said:I am confused by the descriptions of entanglement I have read. Some seem to imply there is a superluminal transfer of information going on, while other descriptions do not. Can anyone explain this simply? I have a B.A. in Math, but am self taught in physics.
Welcome to PhysicsForums!Ron Smith said:I am confused by the descriptions of entanglement I have read. Some seem to imply there is a superluminal transfer of information going on, while other descriptions do not. Can anyone explain this simply? I have a B.A. in Math, but am self taught in physics.
The analog of the entanglement is two coins. Every of the coins gives a random results - head I1> or tail I0> with the probability 1/2.Ron Smith said:I am confused by the descriptions of entanglement I have read. Some seem to imply there is a superluminal transfer of information going on, while other descriptions do not. Can anyone explain this simply? I have a B.A. in Math, but am self taught in physics.
I must say that it seems to me that we may have entaglement with less that 1 correlation. Supose you have two DICES. One entangled state of the upper side numbers of these dices may be:cartuz said:The analog of the entanglement is two coins. Every of the coins gives a random results - head I1> or tail I0> with the probability 1/2.
The coefficient of correlation K of this coins is zero because we have two different random process.
In quantum world for the entanglement we have non-zero coefficient of correlation. In the ideal case is K=1.
You are remember but I employ the definition of coefficient of correlation K=<xy>-<x><y>. Here x and y is two random process between 1 and 0. <> is average. If the process is independent the K=0. For quantum case we are think that the processes is independent but K non-zero. It is very strange for the classical viewpoint.
This is not an accurate usage of the terms. Entanglement is a specialized quantum state involving 2 or more particles. Entanglement itself has nothing to do with the observer.Rade said:Thus the concept of entanglement is the source of the metaphysical nature of reality itself. We also know this fundamental reality of entanglement by its more specific notation: E = MC2.
DrChinese said:This is not an accurate usage of the terms. Entanglement is a specialized quantum state involving 2 or more particles. Entanglement itself has nothing to do with the observer.With respect, I disagree. Entanglement in quantum reality makes no sense without observer. To support my position I offer the following paper summary (see this link for entire paper:http://citebase.eprints.org/cgi-bin/fulltext?format=application/pdf&identifier=oai%3AarXiv.org%3Aquant-ph%2F0106003 [Broken])
Is entanglement observer-dependent?
Italo Vecchi
Vicolo del Leoncorno 5 - 44100 Ferrara - Italy
email: vecchi@isthar.com
Abstract: The properties of quantum entanglement are examined and the role of the observer is pointed out.
...We can now go back to entanglement and ask the question: ”What is entanglement?” .The answer may be: ”Entanglement is the observer’s blueprint for state-vector reduction”. It should be clear that entanglement can be defined only in terms of the observer-dependent basis. Prior to observation all bases are equivalent so that speaking about entanglement is meaningless. It is only when state-vector reduction takes place that the system’s state-vector is cast according to an observer-dependent set of rules . Entanglement has an observer-independent support, since the observer’s perceptions are based on the information it extracts from its interaction with the system’s state vector, which is determined by the system’s evolution. However for state-vector reduction the physical features of the system, as encoded in the system’s state-vector, must be interpreted through a blueprint that depends on the observer. Loosely speaking we may say that physical interaction, as described by the relevant Schroedinger equation, may leave ”marks” on 4 the system‘s state-vecto affecting the measurement outcome, e.g. the scrambling/vanishing of superpositions, but such ”marks” are read according to an observer-dependent blueprint only when state-vector reduction takes place. Without an observer the ”marks” are meaningless ripples on the system’s wave-function...
FYI, the singular of this word is "die" and the plural is "dice". I know no other English word that follows this rule ... what a crazy language!DaTario said:...Supose you have two DICES....
The reason this is not correct is simple. The observer plays a similarly important role an all quantum interactions, including systems where entanglement is not a feature. There is nothing wrong with your quotes per se but they don't tell the entire story.Rade said:With respect, I disagree. Entanglement in quantum reality makes no sense without observer...
Mouse/mice?Nicky said:FYI, the singular of this word is "die" and the plural is "dice". I know no other English word that follows this rule ... what a crazy language!
Rade said:With respect, I disagree. Entanglement in quantum reality makes no sense without observer. To support my position I offer the following paper summary (see this link for entire paper:http://citebase.eprints.org/cgi-bin...nt-ph%2F0106003 [Broken])
I agree with DrChinese. I don't understand why this "quantum reality" bit is only applied to entanglement and NOT to the rest of QM. If one has a problem with "observer dependent reality", then why pick only on the entanglement phenomenon? The Schrodinger-Cat type observation is a HUGE part of this and can't be separated out of any QM measurement, entangled or NOT. The fact that the system of entangled states are in a superposition of a number of possible states IS the whole reason why it is different than a simple "conservation of angular momentum" system in classical mechanics.DrChinese said:The reason this is not correct is simple. The observer plays a similarly important role an all quantum interactions, including systems where entanglement is not a feature. There is nothing wrong with your quotes per se but they don't tell the entire story.
The reason entanglement is so associated with the observer is because it disproves the idea of local hidden variables via Bell's Theorem. That elevates the role of the observer. But it is not a feature solely of entangled systems, it is a general feature of QM. Your quote would be more consistent if you had said: "quantum reality makes no sense without observer".
Is this physics or philosophy?Rade said:To summarize what I think I am hearing about concept of entanglement from the above comments: (?):
1. Reality-[R] exists [An axiomatic statement]
2. Quantum-reality is a subset of Reality-[R], thus quantum-reality exists
3. Quantum-reality makes no sense without observer [DrChinese]
4. Entanglement is a sub-set of quantum reality [DrChinese, ZapperZ]
5. Thus, by logic, entanglement makes no sense without observer [Vecchi paper]
however,
6. Non-quantum reality = Reality-[R] that is not Quantum-reality
7. Non-quantum reality makes sense without observer
which leads to the question
8. Is entanglement also a state of Non-quantum reality ?
This portion of the post is not fully accurate. If you make a measurement of a particle, subsequent measurements will be consistent with the Heisenberg Uncertainty Principle (HUP). A photon with a known polarity will continue to have that polarity as many times as you care to check it. If you make a different measurement, you may then get different results, still obeying the HUP.robousy said:Consider first just a single particle that can be in state A or B. Now this is the important point - when you perform a measurement it can either be in A or B, then if you perform the measurement again a little later - it can AGAIN be in A or B. Just because you measured it A say the first time it doesn't mean it will be in A the second time.
You are too kind.ZapperZ said:Is this physics or philosophy?