wolfgang pauli's exclusion principle

[hamish]

I think that this idea opens up a new possibility of a new era in the comunications sector a magine being able to use this principle for instant comunication no matter what the distance. this principle states that certain pairs of subatomic particles enven when seperated by considerable distances can each instantly 'know' what the other is doing.

[5614]

They cannot 'instantly' know anything. Give me an example and I (or others) will tell you why not. I assume you are talking about Quantum Entanglement and Q Teleportation... in which case the reason it's not faster than light is because a classical means of communication is required to relay the data between the 2 particles (or photons). Currently in labs a laser is often used.

[Klaynos]

Am I being dence or is entanglement nothing to do with exclusion?

[5614]

Yeah Pauli's exclusion and entanglement is quite different, but when people say "seperated by considerable distances can each instantly 'know' what the other is doing." they're usually referring to entanglement, I'm not sure! Hence I said "Give me an example and I (or others) will tell you why not"

[Royston]

Am I being dence or is entanglement nothing to do with exclusion?

 

Not sure if you already know this but Pauli's exclusion theory is purely that (in a closed system) no two electrons can occupy the same state. This also holds for protons and neutrons...photons are different.

 

In more complex atoms it's possible for an electron to occupy two states...but you'll have to ask the experts about this, maybe this is where the confusion sprung from ??

[Klaynos]

Not sure if you already know this but Pauli's exclusion theory is purely that (in a closed system) no two electrons can occupy the same state. This also holds for protons and neutrons...photons are different.

 

In more complex atoms it's possible for an electron to occupy two states...but you'll have to ask the experts about this' date=' maybe this is where the confusion sprung from ??[/quote']

 

Yes exactly that is why I cannot see it having any relation to the question and too entanglement :|

 

And entanglement isn't instantaniouse is it?

[Royston]

Yes exactly that is why I cannot see it having any relation to the question and too entanglement :|

 

And entanglement isn't instantaniouse is it?

 

Entanglement is instantaneous. In fact going back to the original post they're using this very principle for quantum computing and quantum teleportation.

[5614]

Entanglement is instantaneous

NOOOOOOO!!!!! IT IS NOT INSTANTANEOUS!!!!!

(read post #2)

 

Not sure if you already know this but Pauli's exclusion theory is purely that (in a closed system) no two electrons can occupy the same state. This also holds for protons and neutrons...photons are different.

Not technically correct, although it is correct. Pauli said that no two fermions can occupy the same quantum state. Electrons, neutrinos and quarks (and consequently protons/neutrons) are subject to this, so you were right, but it's fermions, not only electrons.

[Royston]

NOOOOOOO!!!!! IT IS NOT INSTANTANEOUS!!!!!

(read post #2)

 

 

Not technically correct' date=' although it is correct. Pauli said that no two [u']fermions[/u] can occupy the same quantum state. Electrons, neutrinos and quarks (and consequently protons/neutrons) are subject to this, so you were right, but it's fermions, not only electrons.

 

Thanks I've just started learning so technical details are needed.

 

I read that it was instantaneous...but information couldn't be sent using entanglement faster than the speed of light...this was in the same paragraph, and confused me greatly.

 

Now it makes sense, wondering if it was just a typo. thanks for putting me straight.

[Royston]

NOOOOOOO!!!!! IT IS NOT INSTANTANEOUS!!!!!

(read post #2)

 

 

Not technically correct' date=' although it is correct. Pauli said that no two [u']fermions[/u] can occupy the same quantum state. Electrons, neutrinos and quarks (and consequently protons/neutrons) are subject to this, so you were right, but it's fermions, not only electrons.

 

Thanks I've just started learning so technical details are needed.

 

I read that it was instantaneous...but information couldn't be sent using entanglement faster than the speed of light...this was in the same paragraph, and confused me greatly.

 

Now it makes sense, wondering if it was just a typo. thanks for putting me straight.

 

Could you elaborate a little further why it's not instantaneous, or provide a good link please.

[Klaynos]

If the information cannot be sent faster than c then how could it possibly be instantaniouse?

 

Neutron stars = cool example of pauli exclusion in action! kinda...

[5614]

It took me a few pages of a thread on SFN and a bit afterwards to understand, but that thread will be too long and a bit confusing (and I said loadsa cr*p in it because I was dumb and ignorant back then!!)... so where's a good place to learn about it. (If you do search for those threads then ignore everything I said and listen to swansont because his posts were always right and most of mine weren't! btw, that was back then and on one topic only!)

 

I spose you could look at like "how would one atom know what the other atom is doing?" the answer being it can't, it needs to be told, or to observe it, it is this process which is limited by the speed at which the information can travel, this limit is c (speed of light in a vacum).

 

I spose this site:

http://en.wikipedia.org/wiki/Quantum_entanglement

is quite good. Ask if you don't understand and we can tell you, I'll look for other sites.

 

[edit]

If the information cannot be sent faster than c then how could it possibly be instantaniouse?

Is this rhetorical?

If not then the answer is that it isn't faster than c and it isnt instant.

[Royston]

If the information cannot be sent faster than c then how could it possibly be instantaniouse?

 

Neutron stars = cool example of pauli exclusion in action! kinda...

 

Well it can't...hence my confusion. Like I said, from what I can remember reading, this was how it was put...and as you've pointed out it's nonsensical.

 

I'll try and find the article...I read it from a load of printouts lying around roughly a year ago.

[5614]

I'll try and find the article

It was either incorrect or you misread it... or it was playing with some stupid technicality which confused most people! Either way finding it won't help much! It'd be a better use of time would be learning what is right!

[Royston]

I spose this site:

http://en.wikipedia.org/wiki/Quantum_entanglement

is quite good. Ask if you don't understand and we can tell you' date=' I'll look for other sites.[/quote']

 

Thanks for the help 5614, I was kinda looking for something with a bit more detail than wiki...I'm going to have a quick scan as well, cheers

[Royston]

It was either incorrect or you misread it... or it was playing with some stupid technicality which confused most people! Either way finding it won't help much! It'd be a better use of time would be learning what is right!

 

I gave up after about 5 minutes !!!!

[5614]

That wiki site does have quite a good content for QE (quantum entanglement)... if you want more than that I don't think I've seen (so I don't currently have a link to what you're looking for) however try searching around.

 

You want something reliable, if it says its faster than light and doesn't go into explaining how a classical channel of communication between the entangled particles is required it may not be entirely correct, well, it isn't really at all correct!

[Locrian]

Let's say you have two photons in an entangled state. When you measure the spin of one, the entangled state function that describes them is no longer in the original superposition, and you thereby know the spin of the other. This happens instantly.

 

When one part of an entangled state is measured, you must conclude the state function of the other is instantly different than you would have described it just before.

 

However, this cannot be used to instantly transfer information.

[Royston]

This maybe way off the mark...but I was thinking, to achieve instantaneous states you need to pass information before hand.

 

With regards to particles there is a slight pause whilst this information is passed.

 

A simple analogy would be two people performing a synchronized event, they would pass information before hand so they could synchronize their actions. I'm not sure if there's any correlation there ?

 

Just a fleeting thought. If a particle behaves according to the response of another distant particle...'it can change the direction of spin', there must be some form of communication between the two.

[swansont]

Just a fleeting thought. If a particle behaves according to the response of another distant particle...'it can change the direction of spin', there must be some form of communication between the two.

 

This is unfortunately a common misconception. You don't change the properties of the other particle, you simply know its state. Once the original measurement is made, they are no longer entangled.

[5614]

Let's say you have two photons in an entangled state. When you measure the spin of one, the entangled state function that describes them is no longer in the original superposition, and you thereby know the spin of the other. This happens instantly.

With photons you have the polarisation of them.

 

It is particles which have spin.

 

For a particle you arrange it in a way that you have 2 of them, one must be spin up and the other spin down. Once you know one of them you can deduce the other.

 

I assume it is very similar with the photons (although I don't know as much about photons being entangled as I do about particles being entangled), I do know it's the polarisation of photons which is entangled.

[Jacques]

What readed for photon was about the polarisation. Entangled photon can be produced by shining an UV photon on a barium cristal leaving two photons having half the frequency of the incomming UV.

Is it possible that the creation of entangled photon always create two photons of opposite polarisation ? It is not mesuring the polarisation of one photon that determine the polarisation of the other. They are always created with opposite polarisation.

[5614]

They are always created with opposite polarisation.

If the setup is correct this is how it works for particles. I would assume it's the same for photons, although I'd wait for someone to confirm it first!

[Jacques]

So what is mysterious about that ?

I have a stick with one end painted in red and the other painted in blue.

I have two box, I close my eyes, break the stick in two and put one piece in each box that I close. I send you one of the box and the other too an other person. When you will open the box and see that you received the blue end. Instantanly you will know that the other received the red end ! HUU fantastic that's magic

[5614]

It's not magic, it's phyics! It's just you can't paint an atom and break it in half!

 

I believe your summary is simple yet correct, for particles anyway.

 

Let's stay with particles, the problem is that people say (they have entangled particles) "look, this is spin-up, therefore, when I discovered this was spin-up I instantaneoulsy made the other particle spin-down" whereas in reality it was always that way, they didn't make anything, they just observerd one and could therefore correctly assume the other's spin.