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Richard J
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What is the difference between entangled and "normal" photons?
What is the difference between entangled and "normal" photons?
Richard
What is the difference between entangled and "normal" photons?
Richard
Richard J said:What is the difference between entangled and "normal" photons?
Richard
No. There is no objective property of a photon (or another particle) that makes it entangled vs. not. Entanglement is only about the relationship between two or more particles - the shared history.mrkilgoretrout said:So is there any way, without knowing the photons' source and without immensely separated detectors, to determine the difference between entangeld and unentangled photons with only one run of an experiment?
The only thing all physicists can agree on (as my other thread demonstrated) is that the probability of observing a particle with an attribute A is correlated with the probability of observing an entangled particle with a complementary attribute A'. For polarized photons, this probability is always related to the cosine of the difference between polarizer angles. There are two possibilities - the photons "knew" at the outset what the polarizer angles would be, and agreed on the outcome, or the photons did not "know" until one or the other struck a polarizer, in which case no one really knows how or why the correlation occurs. One thing that is certain is that it cannot be a "classical" force that causes the correlation because such a force, if it existed, would have to ignore space and time entirely.Is it not true that a measurement which 'disturbs' the attribute of one particle also disturbs that of the other - even if they are separated beyong speed of light contact?
peter0302 said:For polarized photons, this probability is always related to the cosine of the difference between polarizer angles.
Richard J said:What is the difference between entangled and "normal" photons?
f95toli said:Also, it is also possible to entangle e.g. two electrical circuits (solid state qubits) meaning entanglement is not a "property" of a system, whether or not two systems can be considered entangled only depends upon the relationship between.
DrChinese said:I believe there is a discernible difference between an entangled photon and one that is not entangled. Entangled photons do not self-interfere when they are sent through a double slit set-up. This has been pointed out by Zeilinger and others.
DrChinese said:I believe there is a discernible difference between an entangled photon and one that is not entangled. Entangled photons do not self-interfere when they are sent through a double slit set-up. This has been pointed out by Zeilinger and others.
When you discard information about the other particle, you are left with a statistical mixture. (mathematically, this amounts to taking a partial trace) Given a large collection of particles with identical states, you can distinguish between that state being a pure state and a mixed state.kdv said:That's very interesting! But why is that so?!?
MaWM said:There is no such thing as a photon that isn't entangled.
colorSpace said:What do you mean with "relationship" ? Where does it exist if not in "both" photons?
f95toli said:Partly because it is what I work with, but also because photons are "strange" and it is easy to make the misstake of thinking that the effects are due to "propeties" of photons, whereas in fact is just basic QM valid for types many systems.
colorSpace said:If you are saying that entanglement is not a property specific to photons, that is certainly correct, since entanglement isn't limited to photons. What I meant is that the entanglement must be anchored somewhere (or somehow).
So where in reality (unless it has some non-local existence, whatever that would be) might the state of entanglement be located? I don't know, but I wouldn't think that it might be in the physical space between the particles.
f95toli said:Look at the fig.1 in this paper:
http://arxiv.org/abs/cond-mat/0312332
(it is an old paper, but illustrates my point). In this experiment qubit A was entangled with qubit B (the same experiment can be done with more than 2 qubits). Now, it should be quite obvious that the entangled state is not "located" anywhere, the qubits do not move and are obviously not "delocalized" particles.
Entanglement simply means that the two subsystems (qubits) are coupled in such as a way that there are off diagonal terms in the total system Hamiltonian; nothing more.
Entangled photons are pairs of photons that are linked in such a way that the state of one photon affects the state of the other, even when they are separated by large distances. Normal photons, on the other hand, do not exhibit this type of correlation and behave independently of each other.
Entangled photons are typically created through a process called spontaneous parametric down-conversion, where a high-energy photon is split into two lower-energy photons that are entangled with each other.
Entangled photons have been studied extensively in the field of quantum physics because they exhibit a unique property known as quantum entanglement. This allows for instantaneous communication between the entangled photons, regardless of the distance between them, and has implications for future technologies such as quantum computing and cryptography.
While entangled photons can transmit information instantaneously, they cannot be used for communication in the traditional sense. This is because the information transmitted through entangled photons is random and cannot be controlled or manipulated.
Entangled photons can be detected through the use of specialized detectors that are able to measure the properties of individual photons, such as their polarization. These detectors are able to determine if two photons are entangled by comparing their properties and looking for correlations.