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ben_vito t1_j8gmoov wrote

Reply to comment by Weed_O_Whirler in Light traveling through a medium that slows it. Does the same photon emerge? by TheGandPTurtle

I don't follow you on the part about them being unlabeled. If there are multiple photons, why would you not be able to follow and label them, at least from a theoretical and not real life point of view?

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Weed_O_Whirler t1_j8gnkyv wrote

Sorry, I should have been more clear. You can, right up until the point where they collide (you can think of as getting close enough their wave functions overlap), at which point you can no longer know which particle is which.

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2weirdy t1_j8ha2da wrote

>their wave functions overlap

But their wave functions always overlap?

My, understanding was that the "event" that they spontaneously switch, placesis quite low, but always non-zero, and more importantly, indistinguishable from staying still.

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terribleturbine t1_j8h4r7p wrote

Thank you for clarifying. I was looking at my left and right hand thinking "Certainly the electrons in my left hand are not the electrons in my right hand."

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John_Fx t1_j8hv4av wrote

look up the single electron theory where the universe consists of only one electron bouncing back and forth in time.

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tnaz t1_j8mc77f wrote

The single electron universe model fails once you introduce other particles - a muon can decay into an electron and neutrinos. You can't represent that if there's only one electron going back and forth in time.

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tpolakov1 t1_j8jirfo wrote

> "Certainly the electrons in my left hand are not the electrons in my right hand."

You'd be surprised. The states are certainly different, but it makes no sense to talk about electrons, other than the states being filled or not. There is no such thing as "that electron", only "that electron state" and "a electron".

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terribleturbine t1_j8jnj6o wrote

But isn't it true to say "that electron state" in my left hand and "that electron state" in my right hand are states of two separate electrons?

It was my understanding that electrons had a ton of possibilities states/superpositions that they only "chose" one when they became entangled, is it wrong to think of all the possible positions as the "electron" and it's current configuration in my hand as the electron state in this branch of the wave function?

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tpolakov1 t1_j8ju8fx wrote

> But isn't it true to say "that electron state" in my left hand and "that electron state" in my right hand are states of two separate electrons?

They are distinct state, but you can't say that electron 1 is in the left hand and electron 2 is in the right hand. You can say that an electron has filled (or not) the left state and an electron has filled the right state.

> It was my understanding that electrons had a ton of possibilities states/superpositions that they only "chose" one when they became entangled

They stay in superposition until measured, there's no need to bring entanglement into that.

> is it wrong to think of all the possible positions as the "electron" and it's current configuration in my hand as the electron state in this branch of the wave function?

Nope. You can't describe many-particle states by the individual identities of constituent particles as you do in classical physics. When I have three electrons in a bucket, I describe the state of the bucket with electrons in it, i.e., two electrons in the n=1 level and one electron in the n=2 level. But there's no way of knowing which electron is which in those levels.

In the same way, when we're talking about two electrons in your two hands, we describe the state as one electron in the left state and one in the right state, but there's no such thing as left and right electron. This effect is what ultimately leads to things like the Pauli's exclusion principle or the Gibb's paradox, so we know that the electrons fundamentally don't have identities and it's not just a limit of our measurement.

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Purplestripes8 t1_j8h5094 wrote

Location is indeed a way to distinguish identical particles, however if two identical particles share the same location then there is no way to distinguish them. You can not say "which is which", only that two particles came in and two went out.

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drc500free t1_j8j35ct wrote

Think of the individual photons as different locations where a single universal wave function has high density, not as distinct particles. The idea that they are distinct only holds while those locations don't interact and interfere significantly.

Once they interact, the resulting waveform will have other regions of high density. Mapping one of them back to one of the original ones and saying this new photon is the "same" as that original photon is something that might make your brain understand it better by pretending they are Newtonian objects. But it's just a model for understanding, and the further the interaction is from Newtonian collisions the more wrong it will be.

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