Can the history of a particle be traced in principal?

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Q_Goest

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Typically when we consider any particle of matter, one is identical to another. There is no difference between an electron, proton nor atoms or molecules with identical properties. Certainly when we consider an experiment done in the lab, the properties of any particle are consistant. But what about entanglement? Aren't all particles unique in some aspect, regardless of whether they are photons or atoms? Can we really say that if a photon goes into an atom, causing an electron to move between energy levels, that this electron and the atom it's in is not in some way entangled to the source which produced the photon? Is there nothing, even in principal, to tell that the atom which absorbed the photon obtained it from the atom which emitted it? Needless to say, there is an argument which says these atoms are indistinguishable in practice to any other since their properties are identical, but aren't the two atoms now entangled in some way that in principal, can be discerned?
 
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If I give you three particles and tell you that two of them are entangled, I don't think that there is any experiment you can perform which will tell you with certainty which two they are. It would seem to me then that similarly if you had a collection of atoms and a photon emerged from them, even if there was some degree of freedom in which the photon shared entanglement with one of the atoms there would be no way to discern which atom it was...
 

DrChinese

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It does raise an interesting question or two.

1. I am not sure it is meaningful to discuss the "history" of a particle. A particle can be said to have many histories. That is true even with entangled particles.

2. We normally think of entanglement as a rare, difficult to produce scenario. But naturally, there must be - due to conservation/symmetry considerations -many situations in which there is a degree of entanglement between particles. How about the quarks in a proton? Would you call these entangled?
 
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Q_Goest said:
Typically when we consider any particle of matter, one is identical to another. There is no difference between an electron, proton nor atoms or molecules with identical properties. Certainly when we consider an experiment done in the lab, the properties of any particle are consistant. But what about entanglement? Aren't all particles unique in some aspect, regardless of whether they are photons or atoms? Can we really say that if a photon goes into an atom, causing an electron to move between energy levels, that this electron and the atom it's in is not in some way entangled to the source which produced the photon? Is there nothing, even in principal, to tell that the atom which absorbed the photon obtained it from the atom which emitted it? Needless to say, there is an argument which says these atoms are indistinguishable in practice to any other since their properties are identical, but aren't the two atoms now entangled in some way that in principal, can be discerned?
Firstly, Electrons have 'no' detectable size, this enables them to be asigned certain properties and can propergate across 'any' dimension, thus Feynman concured that Electrons can be at any location, forwards or Backwards in Time.

Secondly, Protons cannot be Outside of 3+1 Spacetime, if they encountered..say a 5 Dimensional Space, then they would Decay or Accumilate would be a better description?, into Particles of MORE than 3-Quarks, thay can 'gain' extra mass from the 'extra' dimension, conversely when Protons are dispersed into a lower dimensional setting, they scatter to energies pertaining to the dimension, ie 2-D field energies.

Electrons can boldly go Where Protons may or may not have been, Protons cannot go to an Electron Location..its always Natures way to Produce Electrons that travel to the PROTON!

In this way Electrons Entangle aroun Protons by default?
 

Q_Goest

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Thanks for the feedback. Looks like I took liberties with the word "entangled". Let's ditch that word. I'll try explaining a slightly different way . . .

I've often heard that history can be determined from the present, ie: information can't be lost. Similarly, almost all particle interactions are the same forward as reverse in time - there are few notable exceptions. Hawkings is taking this to an extreme in suggesting even information that falls into a black hole is not lost, that the history of the matter that goes in is imprinted in some way on the matter that comes out when the hole evaporates.

Perhaps the question is,
Can a particle's history be determined? Can the past be determined from the present? Are these not the same question?
 

Q_Goest

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Secondly, Protons cannot be Outside of 3+1 Spacetime, if they encountered..say a 5 Dimensional Space, then they would Decay or Accumilate would be a better description?
I know this gets away from the original post, but is this widely accepted? How can we know that a 5'th dimension has any influence on something like an electron and what that interaction is? What assumptions are being made to arrive at this conclusion?
 

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