Electron Spin Parity

[OneWingedBird]

An interesting theory that an engineer/science buff friend told me about recently, again, something that I can't find a thing about on the net.

All electrons have spin, and can spin in one of two directions. Supposedly some scientists have found that electrons have spin parity, which is to say that there is always the same number spinning in either direction, and if you deliberately alter the spin of one electron, then another will reverse spin by default to maintain the parity.

He thought that this might have interesting repercussions for communications, as apparently the spin reversal occurs instantly rather than at the speed of light.

I'm a bit more sceptical, and not entirely certain how you know which electron is going to reverse it's spin to compensate for the one that you've reversed, or indeed if it's always the same one.

Perhaps someone with a better understanding of quantum physics could shed some more light on this?

Either way, it's still an interesting theory...

 

[escargot]

I have sent off the entire post to my 3rd year Oxford physics undergrad son.

When he can find time between partying I'm sure he'll give it some thought!

 

[OneWingedBird]

Ah, thank you Escargot...

 

[TheOrigDesperado]

I've read several books on this type of thing and I'm no nearer understanding it.

Then again, neither are the guys that write them...

 

[Anonymous]

This is all about the Einstein Podolsky Rosen experiment, and the very much related topic of the Bell Inequality.

There's a very indepth discussion of the issues at
http://physicsweb.org/article/world/11/12/8/1

though I will attempt (post New Year!!!:_pished: ) to draw up a precis of what is going on.

 

[Pete Younger]

There's bound to be an answer here, personally it gave me a headache.

 

[OneWingedBird]

Von Neumann's collapsed prostate confused me...

...until I realise that the article had muddled my head so much that I'd misread 'von Neumann's collapse postulate'.

Interesting, also mindbending, and I'm not sure wether it gives an answer as such.

Maybe this would be simpler if the physicists weren't still arguing among themselves as to wether an electron is an infinitesimal point, an infinitely large field or a dynamic wave function.

Brain hurts. I think I'll just sit back and wait for the expert opinion...

 

[Anonymous]

Electron entaglement

I'll have a bash:
If you think of an electron or other particle as a little spinning gear wheel, you could imagine two of them spinning against each other so they are spinning in opposite directions, then continuing to do so as they drift apart to any distance, and this state is called "entanglement". One of the many odd things about quantum mechanics is that a particle can be in more than one state at a time, so one of our electrons can be spinning both ways at once and only settles down to spinning one way or the other when an act of measurement takes place (bit of a vague concept, something to do with interacting with the "big" world). But the two electrons must still be spinning in opposite directions to conserve the angular momentum, so if one electron is found to be spinning in one direction, the other will have to be spinning the other way.
The upshot of all this is that, if particles are entangled, a measurement of one particle decides the state of both, even if the second is a million miles away from you.
Hope this is of some help.

 

[Twin_Star]

Einstein called this activity "spooky action at a distance", and theorised about its existence long before it was proven.

Modern physicists accept that it occurs, without having any idea why this should be the case. They call it "quantum entanglement"

It is currently being looked into for the next generation of supercomputers (ie: the historical computer uses a system of 1s and 0s to process data, whereas this "quantum" computer could perform, again theoretically, an infinite number of calculations simultaneously. Sort of like the mother of all Hyper-Threading techniques).

This is a nice little article that goes into not only the applications for computers and communications, but also Herr Schroedingers cat, Quantum cryptography and all sorts of other quasi-related topics. Hope you enjoy...

Its from Christian Scientists, but don't let that put you off...