# Tag Info

1

Let us start from the beginning. Elementary particles are quantum mechanical entities. They can be described with the quantum mechanical solutions of the appropriate equations for the set up under consideration with the constants taken from the boundary conditions of the problem. In this it is not different than the situation with classical mechanics ...

-1

There have been conducted many experiments in which light impulses travelled faster than light Are you aware of any scientific publication on major journals officially acknowledging such event? As far as the scientific community knows, there is no such evidence. Even though there were any, this would have nothing to do with quantum entanglement anyway, ...

1

At large energies, the relevant operator does not affect the field theory, so the UV region of the dual geometry of the perturbed CFT (i.e. close to the boundary) is simply AdS. However, when following the RG flow, at some scale the effects of the perturbation set in, this is where the geometry is deformed. For a mass perturbed CFT below the mass scale, the ...

1

In the entangled system we do not have two separate particles. Instead we have a single wavefunction describing a single system. When you interact with the wavefunction you are not interacting with particle $A$ or with particle $B$, you are interacting with a single wavefunction and causing it to change as a result. So the statement measuring $A$ affects ...

0

No, a laser pointer doesn't create entangled photon pair, there is no process involved that would cause it. Until now I haven't heard of entangled more-than-two particles. However now that you've asked I stumbled over a recent publication mentioning entangled photon triplets.

0

A measurement is an interaction that allows some information about a quantum system to be copied. (The information that can be copied is something like the value of one particular observable or POVM, not the whole state.) An entangled state is just a state that can't be written as a product of the state of each system. So $|a\rangle_1|a\rangle_2$ is not ...

0

Let's say you have previously agreed with your friend doing the other measurement that if the combination of spins is up, down you go to the cinema and if it is down, up you go eat a pizza. Now you do the measurement and he does, both just before going out of the lab. You now have excluded two possible future states, i.e., not meeting because one went to the ...

1

On point (1) I can see no reason why it should be impossible, but nobody has done it to the best of my knowledge. On point (2), there is a paper claiming that the AB experiment is entirely a result of local interactions between fields, and that it does not occur if the field interactions are totally shielded. The author claims there was a flaw in the ...

-2

This is the main point which disallows information exchange. No one had yet discovered the way to set a state on one side and to get a correlated information on the other side. If it was possible, many protocols would allow communication. edit bis : If you cannot set the information to send, even if the two sides are correlated, it's not sending ...

0

Let $|\Omega\rangle$ be the quantum state that describes the whole universe. Certainly it doesn't make sense to talk about the entanglement of $|\Omega\rangle$ with something else, since $|\Omega\rangle$ describes everything. However, we can meaningfully discuss the entanglement of the marginals of $|\Omega\rangle$: ...

0

A particle can only be maximally entangled with exactly one other particle. If it helps, you can think of being maximally entangled as having a perfect relationship between two particles rather than either particle having a perfect property in the slightest. If you had a perfect spin up (in a particular direction) then obviously you could have some (that ...

1

The word separable (the property) has a precise and detailed meaning (about lack of factorizability) when discussing multiparticle states. But that meaning might not be the meaning in the context you consider. For instance the paper http://arxiv.org/abs/1302.7188 argues that separability (the principle) is not related to Bell's inequality. And in that paper ...

2

The notion of separability of a state has a precise and simple meaning: In natural language, a separable state of a system that has several subsystems is a state to which a unique state of every subsystem is associated. In classical mechanics, all states are separable in this sense - given two configuration spaces $Q_1,Q_2$, the configuration space of the ...

5

Quantum "teleportation" is a really strange phenomenon, but most popular-science descriptions fall a little flat, indeed. Here's the basic setup for every quantum teleportation experiment: Two particles A and B are entangled and separated. Two more particles, A2 and B2, are put into two special states: A2 is put into some complicated wavefunction state, ...

1

It is not impossible to send information using quantum entanglement. What is impossible is to send information faster than light, violating causality. The quantum teleportation protocol includes a classical step (sending information about one's measurament, if I'm not mistaken), where things are restricted by the usual laws of relativity.

1

In this answer we will stick totally to the Copenhagen interpretation of quantum mechanics. Before the system is measured, there is nothing physical (a consequence of realism not playing a part under this interpretation). There is only our mathematical, non-physical description of the possible measurement outcome called the wavefunction. On measurement ...

2

Answer to your question The term "quantum non-locality" refers to the fact that quantum mechanics cannot be described by a local classical hidden variable model. This is the content of Bell's theorem. In particular, locality is not violated. The statement of the theorem is that if we assume (wrongly) that quantum mechanics is described by a classical ...

1

The average entropy of a part of a state is computed e.g. the following papers: http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.71.1291 http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.72.1148 http://journals.aps.org/pre/abstract/10.1103/PhysRevE.52.5653 http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.77.1 (See also ...

1

When we discuss if QM can be written in classical terms we mean a full description in terms of at least local hidden variables. I can create a simulation of quantum mechanics on a classical computer, but I can't make it correctly simulate entanglement using only local data AKA local hidden variables. That is, if I want to simulate an EPR measurement ...

-1

Entanglement is the name for that what you want have explained. The entanglement is combining two particles like EPR Experiment. Till now nobody can say how it is possible, only the facts are well known - a new level of understanding of quantum relations is pointed up. A quantum computer is not direct compound with these topics. A quantum computer of ...

3

There are a few cases. First case, you measure your particle then you write a letter to your friend and tell your result to your friend before your friend measures their stuff. They can be amazed to know the result of their measurements before they do them. Or they can be unamazed since by then your measurement has had time to affect them without violating ...

1

Simple. SR requires that you cannot pass information outside of your light cone. Measuring EPR doesn't let you pass information on in a speed faster than light. If I were to measure, I'd know what measuring the other particle would result in, but I'd now have no way to transfer this information anywhere instantaneously.

Top 50 recent answers are included