Entanglement Definition and 870 Threads

Hello: Sorry for asking this beginner question: Suppose we have two electrons that are entangled. Now, from what I understand, they are sharing the same wavefunction. Everywhere I read that information cannot travel faster than light in this case because the observer cannot change the state...

I believe I read that the Everett Many Worlds Interpretation resolves the apparent locality problems with entanglement (i.e. the necessity of a faster-than-light influence to explain the correlations between the behavior of entangled particles). If so I'm not sure how. MWI says that the...

Hello all - New to the forums so let me start by saying hi to everyone. ;) Something has always bugged me about considering entanglement effects as "instantaneous." As we all know from SR, moving observers do not agree on simultaneity between two space-separated events. If we...

Look I know I`m a long way from comprehending "entanglement" but could someone help me a bit here. How can we logically say a body is in all possible states until we observe it. Don`t we have to observe it to come to that conclusion? And why can`t Schrodinger`s cat be long dead before we open up...

It is possible to entangle more than 2 photons. A common configuration is to entangle 4 photons, with a common situation as per the following: Experimental observation of four-photon entanglement from down-conversion in which the state is described as (figure 1 of the reference)...

As I understand it FTL communication via quantum entanglement would be impossible since it violates causality, but would it be possible to transfer information using QE slower that the speed of light? I recall reading something like that the receiver would not be able to tell whether the...

A friend asked me this question and I don't have an answer for him: So, we have two particles originating from a common source and traveling entangled in opposite directions and obeying conservation of momentum. After some time the two particles are a fair distance apart. We then make a...

I just had one of those lightbulb thoughts a few minutes ago reading someones post. Does observing some particle in an superposed state entangle you with that particle? It makes perfect sense to me right now.. Its definitely like entanglement, even if it isnt. Observing the first observers...

I have a question that seems simpe: if you have two entangled photons, can you set up two pairs of slits (one pair for the signal photons, and one for the idlers) so that observing which slit the idler goes through tells you which slit the signal photon goes through? It seems that...

If 2 electrons were created at the same time and entangled. And you sent A to the other side of the universe and then you somehow split B. Since the electron being split is connected to the A electron and mimics the electron being split... Would that create matter and would the A electron split...

My understanding is that when you measure an electron's spin on on Axis A, and then on Axis B, the spin on Axis A is "forgotten" and can be something different next time you measure it. Is this correct? If it is, then how does this work across entanglement? If you measure electron A's spin...

Hello, I am interested in the conditions necessary for entangled states to be created. Unfortunately I only have access to introductory QM texts, and they talk about about how entanglement can exists between particles etc, but no mention of the creation of them (and the conditions required...

I downloaded William Donnelly's talk, given at Loops'07 Entanglement Entropy in Loop Quantum Gravity http://www.matmor.unam.mx/eventos/loops07/talks/7B/Donnelly.pdf maybe he will discuss it with us I just had a look

Ill start this question with an example of entanglement (to make sure I have it right). Take two electrons in the ground state of an atom. They are both in the superposition state that is 50% spin up and 50% spin down. You then split these electrons apart, without measuring their state. Now...

People talk about entanglement with such passion and they tell me how big paradox it is, and yet I don't see why. I think maybe I just don't understand quantum mechanics enough? I don't know... Basically you fire two electrons different directions, and then you can measure 50% chance spin up...

That is, entangling two particles and sending one off in a controlled manner (i'm not sure if we're sophisticated enough to even contain a particle in a quantum state without interference so please fill me in) to a black hole and then observing the entangled particle that we kept in some lab on...

Assume there are two particles which share the same quantum states (that is, if I understand correctly, both are probabilistically identical), but have not been through the process of entanglement. Let's assume they never interacted in any dimensions, they just happened to be identical. Would...

Is the Entropy of the Universe Zero?:(Entropy as Entanglement) When I began to fully understand entanglement of quantum systems and what this implies, I was in particular excited by the fact that: a composite quantum system say the composite of two factor systems A and B, can have less entropy...

A friend of mine wrote a paper on entanglement, measurement, and simultaneity. the professor provided an interesting question, which he felt demonstrated a violation of special relativity. Of course, this is most likely due to a lack of understanding on the professor's part, but neither I nor...

Hello, I have two questions I wish to ask concerning Decoherence and entanglement: 1. I am certainly no expert on quantum mechanics, and while I was reading I stumbled upon the concept of decoherence. I understand the idea, but I have a few questions concerning it: 1. theoretically, if the...

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...

I will make this very clear: http://www.physicstoday.org/vol-59/iss-12/p51.html" In fact, I strongly recommend you print this out, and give it to people who are not aware of physics, what it does, how it works, and how it permeates through their lives. This article emphasized so many of...

I'm not buying this for reasons of paradoxes, but Brian Greene is saying that time travel backwards is possible. Source what do you guys think?

Flaw in Anton Zeilinger article (Rev. Mod. Phys., Vol. 71, No. 2, Centenary 1999) This Thread is a continuation from the “Cramer new experiment” thread (see DrC post origin) to separate out comments on an Anton Zeilinger article from the discussion on Cramer ‘Transactional Interpretation’ &...

Ok, I have a handful of questions: 1. Particles A and B are entangled, measuring A colapses the wave function of B, right? 2. The double-slit experiment produces different outcome based on whether or not a particle has been measured, right?

If you have two particles 'a' and 'b' which are entangled with each other and you observe the state of 'a' so consequently you know the state of 'b', if you destroy 'a' will the state of 'b' become unknown again? Cheers Jake

Suppose one prepares two particles in an entangled state (at point S) and that one has detectors (say A and B) at opposite equidistant positions, separated by a large distance from S. Now, if one makes a measurement of the spin at A, the spin at B should SIMULTANEOUSLY change to the opposite...

I'm seeing a lot of articles about refining the entanglement process, and how it should be applicable to information transfer, but I haven't seen any experiments where they have actually manipulated the states on one side to be observed on the other. I'm having trouble understanding exactly how...

I've seen little reference material on my question, except the occasional statement that "that is not the case", but no explanation as to why it is not the case. I suppose this is a common question asked by the layman, but that's me so, I'm asking. If entangled particles are able to...

article which explains "entanglement" who can mention me an article which explains "entanglement" with its applications, its problems & its pitfalls ?

LnGrrR Since the old thread is well off topic from the OP I’ll continue comments on Entanglement in a new thread And try to “Dumb it down" here I assume your have trouble following the details on probabilities and why calculating probabilities for an event of grater than 100% or less...

Assume one photon of a momentum entangled pair of photons is absorbed by an isolated atom. Is there now an entanglement between the other photon and this atom? If so, in what way is the atom entangled with the photon? If the atom after a while emits a photon, under what conditions would the...

just checking: when one particle of an entangled pair enters a magnetic field, the entanglement is gone as it starts to re-align in the magnetic field's direction, right?

Is there such a thing as position entanglement?

These are probably old ideas (or, perhaps, just stupid), but recently thinking about non-locality it seemed to me that (a) non-locality clearly shows that time's arrow IS invariant. Physics texts often point out that if you were to make some kind of movie of a physical event such as the...

Talk about not knowing enough on the topic! But it fascinates me to no end... I've read that, according to Lee Smolin, there are discrete units of space and that there is mathematical support that upon dividing this space, it creates another unit of space of equal "volume". Furthermore...

Could entanglement arise from the continuity of the initial universal singularity?

I know that if you have two entangled particles and measure ones spin, the other one must have the opposite spin, but what if you have 3 particles entangled with each other, what would happen?

Can quantumly entangled particles be used to send information? I've read that if they could, the information couldn't be sent at greater than c. However, the ability, if possible, to send information via this mechanism would allow information to be sent to another place even if the place is on...

Has anyone read something related? Thanks to point me to such papers, and to express your ideas or knowledge. The Mach principle aknowledges that a "frame of inertia" can only be conceived with respect to the whole bulk of nearby universe. That is to say that physics frame of reference is...

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.

Might quantum entanglement explain the cosmological constant, isotropy, flatness, magnetic monopole and horizon problems? Instead of inflation introducing a phase change that caused an exponential expansion in the early universe, perhaps entanglement has maintained a statistical causality...

I read about quantum entanglement in an article about teleportation I read on the web. If two particles can be connected despite an enormous distance, in such a way that the properties of one can be transferred to another, even though no wire or string is linking them, can you use this...

Entanglement and information seem to be the new buzz words in the particle camp, two theories that seem natural to me, but should include QG to make a workable quantum universe. If particles carry information by spin ,and exchange information by entanglement how would gravity communicate?

http://arxiv.org/PS_cache/quant-ph/pdf/0506/0506113.pdf Title: Entanglement in an expanding spacetime Authors: J. L. Ball (Oxford U.), I. Fuentes-Schuller (Oxford U. and Perimeter Inst.), F. P. Schuller (Perimeter Inst.) Comments: I. F-S published previously under Fuentes-Guridi We show...

Say we have \sum_{i,j} c_{ij} |i\rangle_A \; |j\rangle_B which is an entangled state, is there a choice for c_ij we can make that would be a wormhole?

I read up on wikipedia.com about entanglement and teleportation but it left me with a few questions. If you go to This Link. You'll see that they give the analogy "Bob has created two atoms called I and II which are maximally entangled". Now obviously, bob can't create two atoms at will so how...

Soppuse Alice have two particles A and C that are in a partly entangled state |Y(A,C)>. We also have another person Bob (ofcourse) with whom Alice share a pair of entangled particles D and E in the singlet state. Now suppose Alice make a measurement on her two particles C and D, she...

I need a bit of clarity on quantum entanglement... Any of the 'Bell experiments' will do, but for the sake of discussion, I'll reference http://roxanne.roxanne.org/epr/experiment.html . Now, the data is obviously in favor of the predictions of QM. Admittedly, I am currently unable to...

Hi all, 1) does the Compton-scattering produce an entangled state? That is, if I measure the energy of the photon, the energy of the electron is immediately known and vice versa. 2) Can the photon after scattering be considered as a superposition of energy-states? -Edgardo