New answers tagged

0

Teleportation and entanglement do not involve FTL communication of any kind. There is a local description of the evolution of any given quantum system in terms of its Heisenberg picture observables. The observables change only when the system changes by itself or through a local interaction with another system. Entanglement and teleportation can be ...


2

This experiment has been done, first by Birgit Dopfer in 1998, then later by Dr. John Cramer of the University Of WA. In Dopfer's experiment, there was a "coincidence detector" which is basically an AND gate to filter out only the entangled pairs. By moving the detector in the beam of photons not going to the double-slit, the information about the photon's ...


1

For an illustrative example, suppose the state space of a single particle is two-dimensional, say with orthogonal basis $X,Y$. Now consider a two-particle system in the pure state $$\alpha X\otimes X+\beta X\otimes Y +\gamma Y\otimes X+\delta Y\otimes Y$$ with $\alpha^2+\beta^2+\gamma^2+\delta^2==1$. This state is called maximally entangled if $\alpha^2+\...


0

I guess when you say "Are the particles connected through a wormhole or something like that", you are implying faster than light (FTL) signal. The need for FTL signal, to explain entanglement behavior, actually arises from a confusion. It arises due to mixing of two types of correlations involved in entanglement. Anti-correlation (real time) - This means ...


4

No, it simply means that there is a particular kind of statistical correlation between measurements made at the two points. If you measure the state of one, you can infer something about the state of the other; you do not set or influence the state of the other. This is almost exactly the same phenomenon as an experiment wherein one candidate is given a ...


-1

Different interpretations of quantum mechanics will give you different answers. I will not enter in a full discussion of them for that you have wikipedia. Regarding less orthodox explanations that do not violate bell's inequalities, I have heard the wormhole argument before. I prefer instead the idea (just and idea for now) by Wolfram that uses causal ...


0

Basically you're asking if there's some kind of compact-yet-useful way of encoding a graph into the state of some qubits. I think the answer is no. Making a compact representation is easy. For example, suppose your graph is classically encoded by the bits $b_1, b_2, b_3, ..., b_{2^n}$. Then take $n$ qubits and output the superposition $\sum_{k=1}^{2^n} |i\...


1

An approach to define the entanglement between identical particles, is to use the so-called geometric idea. For example, the generic wave function of a fermionic system is not a Slater determinant. However, since the simplest wave function for a fermionic system is a Slater determinant, we can quantify the entanglement between the identical fermions by ...


2

Question 1 is based on the false premise that B measurement does not always obey a 50:50 probability. In fact persons A and B both always have a 50:50 probability of getting a spin up. That particles A and B are entangled means that there is a correlation between the measurements of A and those of B: when A is up, B is down; when B is down, A is up. But this ...


1

Your question 1 has absolutely nothing to do with entanglement, and for that matter absolutely nothing to do with quantum mechanics. You can formulate exactly the same question this way: You and I each have in our pockets a tennis ball that is either red or green. We somehow each know for certain that they are of the same color (and that either color is ...


3

What kind of information are we talking about in superluminal information transport? It might be more intuitive to call it superluminal communication. For the prohibited kind of superluminal information transport, you need to be able to achieve the following. At the start of the protocol, A holds a classical bit which either has value 0 or 1, and which is ...


1

I don't know about sources that emit polarization-entangled photon pairs, but polarization-entangled pairs can be obtained from a polarized source in many ways. One example is Spontaneous Parametric Down Conversion (SPDC). Quoting from Wikipedia: In a commonly used SPDC apparatus design, a strong laser beam, termed the "pump" beam, is directed at a BBO ...


1

While this question is certainly off-topic here, it makes for a fairly nice exercise. Skeptical scientists ... Scientists are sceptical (British c) by definition, so this is an oxymoron. And despite the tone used, scepticism is a good thing. ... keep dismissing the concept of reincarnation based on the fact that there is no need for a soul. ...


1

A book that I highly recommend which covers the said topics is "Lectures on Quantum Theory: Mathematical and Structural Foundations" by Chris Isham. His treatment is more thorough than most textbooks and has some interesting insights. It is also well suited for someone without a deep quantum background. Two books which also covers these topics and are ...


0

If two particles are entangled and then separated, will affecting one of them affect the other? If the state space for particle $i$ is $H_i$ and $U$ is a unitary operator acting on $H_1$, then $U$ acts on $H_1\otimes H_2$ (that is, the state space of the entangled pair) as $U\otimes 1$. If affecting one particle affects the other, then how is it not ...



Top 50 recent answers are included