Entanglement Definition and 880 Threads

How can we be so sure? I know it's fast ..but, what if it swaps by the speed of light instead? I know there are some experiments that try to rule this out, however, I don't think they take into consideration that the signal to swap may be initiated by the action that observes one of the...

Bell's theorem debunks theories concerning local hidden variables. Many people interpret that as the complete absence of local hidden variables. Hidden variable theories were espoused by some physicists who argued that the state of a physical system, as formulated by quantum mechanics, does not...

Can all types of particles be entangled? Do they have to be the same (electron/electron, etc.) Can more than two be entangled? How do you entangle in the first place?

I'm not asking about two way or even repeating communication. Is it possible to entangle particles, keep then entangled and send half of them far away, and delay their choice for an arbitrary amount of time? What I'm thinking about is asking a yes or no question: Is there life on Planet X? So...

I've recently been reading about entanglement between two spatial modes of a single photon. It's a little over my head and there is one aspect about it that I'm particularly unclear on, which I was hoping someone here might be willing to shed some light on it. The basic setup is described with...

Hello Everyone, I would like to understand entanglement a little more clearly. My understanding is that two or more quanta (for example photons) that are entangled become a single entity. Entangled or not, there is always a single and total wavefunction that describes the system but in the...

I'm trying to read this paper. Right now my problem is with equations 3.16 and 3.17. I understand that in equation 3.16 we're putting some boundary conditions on the fields, but I have two problems with these boundary conditions: 1) The fields depend on both ## t_E ## and ## x##, i.e. ##...

Assuming two particles are entangled, is there a quantifiable energy associated with separation distance? Rephrasing the question: If two entangled particles are distance x1 apart and another pair of identical entangled particles are distance x2 apart, is there a difference in the energy...

I'm just an interested layman with no back ground in physics so please excuse my ignorance. As I understand it, due to the uncertainty principle it isn't possible to know both the X and Z spin component for example, of an electron simultaneously. So if I took pair of entangled electrons and...

Hasn't anyone or others thought of this before.. entanglement using wormholes seem to be quite obvious and logical. According to Jun Maldacena in November 2016 issue of Scientific American (see...

Can two particles be entangled in the energy property/observable? If so, what kind of experiment could verify that the two particles were energy-entangled? Thanks in advance.

http://onlinelibrary.wiley.com/doi/10.1002/lpor.201500252/abstract https://arxiv.org/pdf/1509.06217v2.pdf "...it has been implicitly assumed that this scheme is of inherently nonlocal nature, and therefore exclusive to quantum systems. Here, we experimentally demonstrate that the concept of...

I'm reading this paper. But I haven't read anything on how to calculate the density operator in a QFT or how to calculate its trace. Now I can't follow this part of the paper. Can anyone clarify? Thanks

Hello, I have red on the web about the entanglement, but there is one thing that it is not clear to me: to explain it, why we cannot just say that randomness and correlation between the two entangled particles is happening at instant of their creation and from that time on they stay in that...

I understand that one way of creating quantum entangled electrons is by splitting a Cooper pair. Is then their spin property used in the measurement, as this must always sum to ##0## for a Cooper pair? If that is the case, do quantum entangled electrons only exist in the singlet state, where the...

As I understand it most, if not all, experiments carried out to test Bells theorem test the local hidden variables assumption that photons have definite polarisations. What I would like to know is whether experiments on properties other than polarisation have been carried out. If not are there...

I've been doing a course on Quantum Computing and I haven't managed to figure out so far how entanglement would be a useful resource on a general purpose quantum computer. By general purpose quantum computer I mean some theoretical device that could possibly replace current classical computers...

If I shine a laser beam through a calcite crystal, the beam is split in two, as shown below. Are the photons in the split beams in an entangled state?

If we don't know the polarisation state of a photon before detection is it reasonable to assume that it's in a superposition of all possible states? Thank you if anyone can clarify.

Scientific American created a short movie purporting to explain entanglement and the Bell experiment at: http://www.scientificamerican.com/video/quantum-entanglement-the-movie-2012-01-30/ The part that interests me is near the end when explaining what is possible with entangled photons, which I...

It is said that entanglement doesn't violate relativity because there is no information transferred. Ther reasoning being Bob and Alice only get randomness even if there is correlation. But can random energy be transferred as it is still random? For example. Entropy decreasing at one place and...

In this video Murray Gell-Mann discuses Quantum Mechanics and at 11:42 he discuses entanglement. At 14:45 he makes the following statement: "People say loosely ,crudely,wrongly that when you measure one of the photons it does something to the other one. It doesn't." Do most physicists...

If you have a pair of particles (perhaps atoms for example) that are entangled, and one of them is mixed in amongst a whole bunch of other atoms of the same species, yet not entangled; could you differentiate in some way the entangled atom from the rest WITHOUT destroying the existing state of...

Suppose we have a pair of entangled particles. Suppose the first particle of the pair interacts with a macro-object and decoheres. Does the macro object get entangled with the second particle?

First let me ask this: Consider a pair of entangled photons fired at a respective detector after passing respective polarisation filters. If a photon passes a polarisation filter, is it in a superposition of having passed and not having passed? Is the measuring device (that detects the...

I apologize in advance that this is not the usual format. I don't have a specific question, and it's not out of peer review just yet, but this new study seems pretty interesting overall. Does anyone here want to share any thoughts on this? Seems pretty darn interesting to me...

Hi everybody! Wasn't sure whether to post this here or in Quantum Mechanics, decided I would start here. I was wondering how the entanglement structure between the nucleons of two nuclei would evolve during a fission event. Correct me if I'm wrong but wouldn't the two sets of nucleons...

This is an observation I'm making that seems like it is wrong but I can't figure out why it would be. Entanglement links two states together. For example the spin angular momentum of particles. An entangled state of two particles could be where you know if one particle is measured spin up the...

Please forgive any ignorance in advance, I have a lot of general science knowledge but know little about physics. I'm not sure if two particles with mass can be entangled, but if they can what happens if you entangle two particles while only one is accelerated, do they both gain mass, or only...

Hi all, I start to read some popular science on quantum physics. The term "entanglement" appears everywhere in quantum communication and other related fields. I am trying to understand this concept based on my undergraduate knowledge on physics. From some online resource, I have a feeling that...

Hi all! I know that the singlet state is entangled. Is the center triplet state also entangled? At first blush it seems like it should be as the state expression has the same structure with the minus sign replaced by a plus. Thanks in advance!

I have two photons that are entangled and exist in all possible states simultaneously. By measuring photon A, I cause the superposition to collapse, and i can see that it has a certain spin (say left). This measurement also causes photon B's superposition to collapse, but will it be spinning...

Consider the original paper, ON THE EINSTEIN PODOLSKY ROSEN PARADOX by J. S. Bell from which the following quotes are taken: “Since the initial quantum mechanical wave function does not determine the result of an individual measurement, this predetermination implies the possibility of a more...

I've been pre-occupied with Heisenberg's uncertainty principle for around four years now, and I've come to fabricate a lot of questions. The most pressing one, however, is as follows: To me, the uncertainty principle seems to reference our (relatively) poorly controlled methods to measure a...

Suppose we have a source of polarization-entangled photons, that fires pairs of photons in opposite directions at two detectors with orientation-adjustable polarizationfilters in front of them. Obviously, there is a correlation between the orientation of the respective filters and the joint...

Hi. Why did the founding fathers of QM know that the Hilbert space of a composite system is the tensor product of the component Hilbert spaces and not a direct product, where no entanglement would emerge? I mean today we can verify entanglement experimentally, but this became technologically...

Hi. In most articles on Bell's inequalities, both the reality and locality assumptions are thrown at the reader from the beginning. DrChinese however starts with only the reality assumption and shows that it doesn't comply with QM IF it were possible to measure two non-commuting observables...

I am studying the history of Quantum Mechanics and was reading about particle entanglement. What I would like to know is how did Einstein see that particle Entanglement meant that particles would be affected by spooky action at a distance. I guess that spooky action at a distance may also be...

The question refers to this paper : http://arxiv.org/abs/1606.00672 I am having difficulty understanding the idea behind this. How can we possibly be able to unambiguously detect any left-over traces of entanglement here ? If I understand this right, the thought process is that an entanglement...

Hello guys, I have few questions about the well-known quantum tunneling. I'll start off with the animation from wikipedia So question #1 why doesn't the barrier collapse the wave function, is that even possible? What's the difference between the barrier and the measurement screen in double...

I have a question that seems to reflect my main concern with QM. Here it is: Consider a series of polarisation-entangled photon pairs that are sent in opposite direction to two measuring devices (e.g. at opposite ends of the universe). The measurement consists of detection of a photon after...

Once I heard a fellow-layman on QM say that he imagined two entangled particles never been separated in the conceptual sense, that is: the two particles are conceptually 'one', only they connect two parts of spacetime, and are so able to exhibit correlations over spacetime with respect to the...

If I'm correct, a series of with respect to some property entangled particles exhibits a correlation between several measurements of that property by means of two measuring devices. My question is: is it possible that between measurements the physical constitutions of the measuring devices...

My understanding is that when two particles are entangled, then when you get a measurement of one particle, then you already know the outcome of a similar measurement for the other particle. But as far as the measurement of the other particle, I thought it would be probabilistic. But...

Following scenario: One million entangled photon pairs are created and are sent to Alice's and Bob's laboratory such that Alice receives 1 million photons(or any other large number) of which each is entangled to one of the million photons Bob receives, their laboratories being at a distance to...

Just taking an advance in what I want to learn someday: I understand that decoherence and entanglement are more or less equivalent. So, I take it decoherence is in principle a process of entanglement. Consider two particles A and B who are entangled. if A decoheres by interacting with particle...

Suppose we fire two entangled particles in a tour round-flight around the galaxy and measure their spins using two Stern-Gerlach devices after returning back to the earth. Will the correlation between their spin measurement still obey quantum correlation? According to General Relativity...

Just watched many times (specifically @ 20:13 - 25:04) Ron Garret's 'Google Tech Talk' All was going well - the 2 photon experiment & concept visualised - only that the finality of comprehension wasn't delivered... perhaps because Ron was merely using this for his own purpose. This seems a...

Does measuring a polarized photon after it passed a polarization filter put the measurement apparatus in a superposition of detected/not-deteced (the photon)? Does this depend on whether the photon is part of an entangled pair?

I recently stumbled across quantum entanglement and thought of an experiment. I know that the laws of physics forbid FTL communication, can anyone tell me what's wrong in my following experiment? Information, in classical bits, consists of two states, 1 and 0. To my shallow knowledge, when an...