Epr Definition and 121 Threads

Hello, I've read through several sources about the EPR Paradox but I'm not sure I'm understanding everything. I know that: -the paradox in question seems to be due to a violation of the principle of locality -there is no useful transferred faster than c regardless of which axes the two...

Hi, I have this one boggling my mind for quite some time. Let's consider a very simple EPR experiment -- pair of entangled particles are sent to Alice and Bob (separated by large distance), who (at the same time) measure its spin along different axis: Alice does the measurement on axis z...

EPRB is a know reasoning about the singlet state. However if we apply this to the triplet state \frac{1}{\sqrt{2}}(\mid+-\rangle+\mid-+\rangle). we find the following : suppose we measure spin A with result +, then spin B is - (we see this by the projection on the possible state)...

If we have twin photons moving in the opposite direction. For the first photon we can pass it through a polarizer that will either output a photon with vertical polarization or a photon with horizontal polarization. after this experiment we now know what will the other unobserved photon...

I have a question regarding the paper by John Bell (www.drchinese.com/David/Bell_Compact.pdf‎ ) in which he shows that a certain hidden variable approach cannot reproduce the expectation values predicted by QM for a pair of particles in the singlet state. After eqn 15 on page 4, I don't...

Morrobay suggested we split off this discussion from another thread. I will post my summary of the EPR definition a bit later today.

I keep looking at these experiments that demonstrate violation of Bell's inequality and I really can't figure out why anyone cares. The scenario always seems wrong in some way. For example the EPR paradox. The argument goes like this, if you start out with a source of entangled "photons"...

In quantum physics, a wave function instantaneously collapses once an observable is measured. For instance, if an electron's angular momentum in the z direction is measured, then the angular momenta in the x and y direction immediately become indeterminate due to the Heisenberg Uncertainty...

Hello dear readers, I have a problem. I'm giving a lecture tomorrow on the EPR experiment and Bell's theorem and so on. I had the feeling I really understand the essence of the EPR thought experiment. However, a few hours ago I just had a disturbing thought (while practicing the lecture in...

Sorry, I have 2 doubts about the EPR paradox. 1) Just check out if I am ok: What EPR proposed was that QM suggest that if two entagled particles, for example photons, prepaired in some special way, get away from each other then: a) if we measure their x-spin then one particle will get the...

New "loophole free" EPR test with photons by Wittmann et al Recently posted under Recent Noteworthy Physics Papers, https://www.physicsforums.com/showthread.php?t=127314&page=10: Bernhard Wittmann, Sven Ramelow, Fabian Steinlechner, Nathan K Langford, Nicolas Brunner, Howard M Wiseman...

I am in the process of trying to understand, in basic terms, how the many-worlds interpretation (MWI) might explain the EPR experiment. In this context it is hoped that the scope for what appears to be almost unlimited speculation might be reduced. It seems that the original EPR experiment of...

Hello I have been thinking at EPR experiment during some time. It is very suggestive for me that the entanglement effects travel faster than ligth between the positions of 'Alice' and 'Bob'. I understand this is not contradictory with special relativity, due there is a not real exchange of...

Consider 2 entangled fermions. If the spin direction of one particle is measured, then the spin direction of the other is instantly determined, regardless of the distance between them. This is the famous EPR-type experiment in non-relativistic QM. This implies that time is absolute, in...

In the book "Quantum: Einstein, Bohr, and the Great Debate about the Nature of Reality", the EPR was told in somewhat different way than other sources I have read. I don't know if it is the original views. The arguments goes like this and very simple. In Copenhagen, In the absense of a...

We consider a typical version of the EPR paradox where an electron and a positron are produced collinearly in the +y and -y with the spins polarized in the positive and negative z directions. The pair is emitted with zero linear and zero spin-angular momentum. If the positron is detected in the...

So I understand local realism (the moon is there when we aren't seeing it) and the notion that Bell's Theorem says that if local realism is true, then we could perform experiments that show observation is independent of reality and that we should expect certain probabilities to arise. But we...

HAPPY 76th BIRTHDAY! EPR 25 March 1935 - 25 March 2011 From your many supporters at PF and beyond. Especially those still motivated by your final paragraph: "While we have thus shown that the wave function does not provide a complete description of the physical reality, we left...

dBB, as a theory with hidden variables, must be non-local. So there is some magic how 'particles' affect each other with superluminal speed. I don't care about the details, I know that somehow these rules are adjusted to satisfy Bell. My questions: 1. is dBB also 'compatible' with GHZ? 2...

Does in EPR problem transfer anything between two particle? If it transfer, then it violates principle of special relativity. Is this statement true? Thanks

the source from where i read about the above experiment also mentioned that the outcome is favoured for bohr's point of view( mathematically equations by bell)... if that's true____ why relativity limit of speed of light?

EPR paradox-failure?! Can anyone please explain to me why the EPR paradox failed to bypass the uncertainty principle? I would appreciate it if minimal maths is used, because I am still a high-schooler and don't know much about higher math.

Suppose that we focus our optical or radio telescope on a star or galaxy R light years away. If we continually measure the polarity of the photons received and continually get definite results, then we know that at the location 2R from us, the location is empty of matter; ie, no detection...

Does anyone know of a good discussion of the compatibility (or otherwise) of Weinberg's 'cluster decomposition' principle with the fact that entangled states yield distant but correlated measurements?

"Prior interaction" as an unwarranted assumption of EPR I think it should be understood that the concept of "entanglement" is not native to the mathematical formalism of QM, but only comes to us with Einstein's assumption (in the EPR paper) that there is an initial, composite wavefunction that...

Is action at a distance possible as envisaged by the EPR Paradox?

Hello, i have a question regarding the Many World Interpretation of quantum mechanics and how it explains the entanglement of two particles.. From my understanding, entangling two particles so that an observable of one (es. spin of z axis) is correlated with the same observable of the...

I have a new-b question. From Dr. Chinese's page I get this quote "EPR had a simple but powerful definition of what they called an "element of reality": IF an observable property of a system could be predicted with absolute certainty (100%) without disturbing that system, THEN it must...

I'm slowly working my way through what I need to really understand the Bell papers. Everyone says that a good start is the EPR paper. I understand that Einstein may not have read the final version before publication and may not even have wanted his name appended (sort of convoluted logic and...

In the following link below, consider page 2, paragraph 2 ("To illustrate the ideas involved..."). The author Podolsky considers a particle with a 'single degree of freedom.' Then in eq. (6), he shows a true cartesian coordinate system. Isn't this an inconsistency with the paper? And as...

I read some about EPR and the way it seems to contradict SR and I don't understand this: Since we are talking about not relativistic QM isn't it natural for it to contradict SR, for instance, Newton 3rd. law (action and reaction) contradicts the finite velocity of interactions but nobody...

Lets look at two mind experiments. Experiment 1. We generate pair of entangle photons in opposite polarization states. At Alice's wing we have polarizer with polarization axis oriented vertically and detector that registers "clicks". At Bob's wing we have the same setup - polarizer with...

Can somehow confirm that my understanding of the EPR Paradox is correct. Here goes... Essentially you can entangle two photons, and send them in opposite directions. If we detect one of the photons, we can find out its properties, and since the properties of the two photons are linked, also...

Hi, I am little bit lost in what is so called EPR paradox (see also http://en.wikipedia.org/wiki/EPR_paradox). It takes into account two particles A and B that have some "same" characteristics (states) and by messuring some of this characteristics of particle A implies that the same...

Greetings! This is my first post so go easy. I read through the thread addressing the Sci Am article claiming that entanglement violates relativity. The article actually addresses a symptom of a larger issue that exists between QM and SR. I would like to get feedback on this issue as...

Trying to be clear on EPR... Hi - I've been reading this article on quantum physics and I'm getting a little lost... I don't know anyone I can ask about this stuff - particularly since most of the math is still a few years away for me and I'm an accountant, not a physicist... if anyone has a...

Further to my recent post on not understanding why physical length contraction in Lorentzian relativity doesn't imply an empirical difference with Einsteinian STR: It seems to me that Bell's theorem and the Aspect EPR-style experiments demonstrating non-locality in quantum mechanics imply an...

Assuming a system A with v=.8c wrt system B At x=0 in A we have 4 EPR "transmitters" wih receivers at x=10 , x=(-10) in A and x'=10, x'=(-10) in B At x=0=x' at time t=0=t' an instantaeous epr polarization event is transmitted simultaneously by the four transmitters. Can anyone suggest...

What would happen if adiabatic processes were applied in the context of a long-distance EPR Experiment? As background for my questions, see http://en.wikipedia.org/wiki/EPR_paradox" ) In the context of the foregoing, please visualize two particles that are...

was original EPR paper (as written by Einstein) contradicted uncertainty principal or was it against the copenhegon interpretation of QM? please tell me any website where original EPR paradox is discussed.

consider two interacting photons in the EPR effect. the photons separate and move towards different detectors 1 km in each direction. measuring the first photon instantaneously affects the other photon. how much has teh first photon aged? how much has the second photon aged?

hello I got al little bit confused about spins flipping in an EPR experiment. As far as I know, the idea of EPR is to measure the absorption of an electromagnetic wave induced by spin flips if the energy is conserved by \hbar \omega = g_{spin} \mu_B B_0. But now I heard several times that a...

Hi everybody, I'm trying to study the topic of teleportation, and thus want to understand the EPR paradox. could you reffer me to some readings? (I have only basic background with quantum mechanics, so I would appreciate some basic explanations on reality, locallity, the paradox itself...

The philoshophy is confusing me. If i understand correctly, it comes down to the following: when a pion decays (which decays to an electron and positron), we can make a measurement of the spin of both resulting particles. If I measure the spin in the z-direction of the electron, I instantly...

Does anyone know of a reference that describes the effect of adding a quarter wave plate or even a half wave plate placed at 00 / 90 0 and 450 positions in just one leg of a EPR entanglement polarization experiment. This would be in addition to the half wave plate in each leg already in place...

Hi. I have read a little about the EPR paradox; however I haven’t fully understood it yet, therefore I was hoping for someone to answer my questions, so I can get a better understanding. I have read the link underneath, however I don’t get it. http://en.wikipedia.org/wiki/EPR_paradox...

Hopefully, this caught the attention of VanEsch.. :biggrin: Let's say Bob and Alice do an EPR type of experiment. A gazillion entangled pair of photons is sent to Bob and Alice who are 1000 light years apart. They measure the spin of the photons. They do not know yet that this violates...

Apparently I didn't make clear what bothers me. I'm happy to set aside the silliness of there being two Bobs, one in each branch that occurs after Bob makes a measurement. And I concede that your idea of choosing, at random, by the Born rule, one of those branches for Bob's consciousness-token...

Simply put the EPR paradox argues that the fact QM predicts that a measurement at A affects reality at B instantaneously, means that QM is violating the speed of light limit. I ask for a clear proof or explanation of how QM does not violate the speed of light limit in EPR type experiments as...

I don't see why the EPR thought experiment would ever be concieved as a way to demonstrate anything against QM... (you can find an explanation of the EPR thought experiment here: http://en.wikipedia.org/wiki/EPR_paradox) Ok before Alice measures anything P(+z)=0.5 and P(+x)=0.5 for both...