A Conversation for Quantum Mechanics

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Post 1

Peet (the Pedantic Punctuation Policeman, Muse of Lateral Programming Ideas, Eggcups-Spurtle-and-Spoonswinner, BBC Cheese Namer & Zaphodista)

"This state actual corresponds..." - "actually" smiley - erm


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Post 2

Peet (the Pedantic Punctuation Policeman, Muse of Lateral Programming Ideas, Eggcups-Spurtle-and-Spoonswinner, BBC Cheese Namer & Zaphodista)

"...the average energy (2.25 eV in the case of the superposition state above) is observed."

I may be showing my stupidity (plus I've just drank a lot of smiley - cider) but from my interpretation of what I read shouldn't that be 1.75 eV? If not, where did I go wrong? The article implies an equal chance of seeing 1.0 eV or 2.5 eV, making the average over multiple observations tend towards 1.75 eV. Or I'm talking b******s...? smiley - geeksmiley - erm


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Post 3

U195408

Hi

when I wrote this I thought that was right, but now it looks like I was wrong. I'm still recovering from major surgery, but I think you're right, the energy should be

0.5*(1 ev) + 0.5*(2.5 eV) = 1.75 eV

Sorry about that.

Dave


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Post 4

Peet (the Pedantic Punctuation Policeman, Muse of Lateral Programming Ideas, Eggcups-Spurtle-and-Spoonswinner, BBC Cheese Namer & Zaphodista)

Not a problem, Dave - at least it proves I read it... smiley - ok

Hope you feel better soon! smiley - cheerup


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Post 5

Cefpret

First of all -- all the best for Dave!

Could someone give me an example for such an averaging? I know only the case when you see two distinct signals, one at 1eV and the other at 2.5eV, maybe different in strength but not collapsing to one 1.75eV peak.


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Post 6

Smij - Formerly Jimster

I've fixed these now.

Jims


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Post 7

Peet (the Pedantic Punctuation Policeman, Muse of Lateral Programming Ideas, Eggcups-Spurtle-and-Spoonswinner, BBC Cheese Namer & Zaphodista)

Thanx smiley - ok


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Post 8

U195408

As far as the averaging is concerned, this might be determined by the experimental setup. For example, the energy spacing might be much closer together (1 eV and 1.1 eV), and the experimental resolution not sufficient (0.3 eV). This would result in a lump peaked at the average value.

This isn't the best example though, let me try to think of something better.

Dave


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Post 9

Cefpret

I assume when you say '[if] a large number of measurements are made repeatedly on the system [...] the quantization is washed out' you want to give an example for the transition QM --> classical ('our') world.

But this transition is done by making h smaller and smaller, which may mean eg that the discrete states come closer and closer and turn into a continuum eventually. This would be some sort of washing out.

Another sort of washing out is if there is a repeated measurement with very many eigenstates, eg photons through a slit. But the result is a mere statistical distribution over all those eigenstates, there are no 'new' ES coming into existence like your 1.75eV.

Granted, your experimental setup may be imperfect, but that can be the case in 'normal' experiments, too. No QM effect.


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