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Dorilian
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If I give you a black box and two photons go out of it (not necessarily in opposite directions), how can we know if the photons are entangled?
One can't. But if the box produces _many_ pairs of photons, one can calculate statistics and decide on the basis of that.Dorilian said:If I give you a black box and two photons go out of it (not necessarily in opposite directions), how can we know if the photons are entangled?
A. Neumaier said:One can't. But if the box produces _many_ pairs of photons, one can calculate statistics and decide on the basis of that.
Entanglement is a quantum phenomenon in which two or more particles, such as photons, become correlated in such a way that the state of one particle cannot be described independently of the other.
No, entanglement cannot be observed or measured directly. Instead, scientists use indirect methods such as entanglement witnesses or Bell inequality tests to determine if two particles are entangled.
One method is using a process called spontaneous parametric down-conversion, where a crystal is used to split a single incoming photon into two entangled photons. Another method is using quantum dots, which are semiconductor structures that can emit entangled photon pairs when excited by a laser.
Scientists can use various tests, such as the Bell inequality test or the CHSH inequality test, to verify if two photons are entangled. These tests involve comparing the correlations between the two photons to certain rules that are predicted by quantum mechanics.
Entangled photons have potential applications in quantum communication, quantum cryptography, and quantum computing. They can also be used in precision measurements and in testing the foundations of quantum theory.