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StevieTNZ
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When you create a pair of entangled photons, are they simultaneously in a superposition of V and H, and 45 and 135 polarisations?
Antientrophy said:This is were Heisenberg's uncertainty principle comes in. The more precisley you try to measure the state of one photon, the less likely you will understand or reveal the state of the other.
StevieTNZ said:I'm not sure I follow. Before we make a measurement of one of the entangled photons, what superposition of polarisations is it (V and H AND/OR 45 and 135)?
Also, when I measure one photon and the polarisation turns out to V, I know the other photon has taken on V polarisation. I don't see where the uncertainty comes in there?
questionpost said:They are uncertain because they aren't being measured.
All mass particles in an entangled state are uncertain, but their states such as with spin are uncertain (or indistinguishable from each other) but always opposite since they are occupying the same quantum state and therefore have to have opposite spin. I don't know about photons though, because non-mass particles don't have to occupy opposite spins to exist in the same quantum state.
StevieTNZ said:Yes, but you usually can describe the superposition they're in when not being measured (hence wave functions). Uncertainty is a property of measurement results.
questionpost said:So what's your actual question?
StevieTNZ said:I've stated it already.
Wouldn't that depend on the history of how the photons were created? Let's say you annihilate a positron and electron to make the photon pair, then I should think the photon pair will inherit the conserved attributes of the initial pair. But one thing is clear-- you cannot talk about an entangled system in language that refers to superpositions of states for the individual particles. An entangled system is a superposition of two-particle states, where the two-particle states are tensor products of single particle states. Is it not so?StevieTNZ said:When you create a pair of entangled photons, are they simultaneously in a superposition of V and H, and 45 and 135 polarisations?
Entangled photons are a pair of photons that are intrinsically connected to each other, meaning that any change in one photon will instantly affect the other, regardless of the distance between them. This phenomenon is known as quantum entanglement and is a fundamental principle in quantum mechanics.
Entangled photons have a wide range of applications in scientific research, particularly in the field of quantum information and communication. They can be used for secure communication, quantum computing, and quantum teleportation, among others. They also provide insight into the fundamental nature of quantum mechanics and its implications.
Entangled photons can be created through various methods, including spontaneous parametric down-conversion, parametric amplification, and four-wave mixing. These methods involve splitting a photon into two entangled photons with opposite polarizations and matching wavelengths.
V/H polarization refers to vertical/horizontal polarization, where the entangled photons have perpendicular polarizations. On the other hand, 45/135 polarization refers to diagonal polarization, where the entangled photons have polarizations that are 45 degrees apart. These polarizations are important in measuring the correlations between entangled photons.
Entangled photons hold great potential for various applications in the future, such as secure communication, quantum encryption, quantum computing, and quantum teleportation. They could also lead to new technologies and advancements in fields such as medicine, biology, and materials science.