QUIP

[Nephew Twiddleton]

When particles decay in to other particles, these decays must obey the various conservation laws. As a result, pairs of particles can be generated that are required to be in certain quantum states. For ease of understanding, consider the situation where a pair of these particles are created, have a two state spin and one must be spin up and the other must be spin down. As described in the introduction, these two particles can now be called entangled since you can not fully describe one particle without mentioning the other. This type of entangled pair where the particles always have opposite spin is known as the spin anti-correlated case. The case where the spins are always the same is known as spin correlated.

Now that entangled particles have been created, quantum mechanics also holds that an observable, for example spin, is indeterminate until a measurement is made of that observable. At that instant, all of the possible values, that the observable might have had, "collapse" to the value that is measured. Consider, for now, just one of these created particles. In the singlet state of two spin, it is equally likely that this particle will be observed to be spin-up or spin-down. Meaning if you were to measure the spin of many like particles, the measurement will result in an unpredictable series of measurements that will tend to a 50% probability of the spin being up or down. However, the results are quite different if you examine both of the entangled particles in this experiment. When each of the particles in the entangled pair is measured in the same way, the results of their spin measurement will be correlated. Measuring one member of the pair tells you what spin of the other member is without actually measuring its spin.

The controversy surrounding this topic comes in once you consider the ramifications of this result. Normally under the Copenhagen interpretation, the state a particle occupies is determined the moment the state is measured. However, in an entangled pair when the first particle is measured, the state of the other is known at the same time without measurement, regardless of the separation of the two particles. This knowledge of the second particle's state is at the heart of the debate. If the distance between particles is large enough, information or influence might be traveling faster than the speed of light which violates the principle of special relativity. One experiment that is in agreement with the effect of entanglement "traveling faster than light" was performed in 2008. the experiment found the "speed" of quantum entanglement has a minimum lower bound of 10,000 times the speed of light.[5]

From Wikipedia...

Holy shit 10000+ times the speed of light?!?

So, I think I get it now. Damn. And they do not become disentangled because they're halves of the same particle.

Actually, some scientists have observed what is called "entanglement sudden death" which basically results is a clean break between the two particles. Though last I read, no one has figured out what the hell is going on there.

I think being a quantum physicist must be fun... get up in the morning, observe an experiment, become confused, go get drunk and go to bed.

And get paid for saying, "Uh, nothing makes sense"

[Captain Utopia]

At least the scientists in the past who made their discoveries in the patterns made out of chicken intestines, were a more honest form of hustler.  I declare QM to be nothing more than an elaborate hoax meant to keep brainy math dudes in a constant supply of nubile and gullible undergrads.

[Bebek Sincap Ratatosk]

At least the scientists in the past who made their discoveries in the patterns made out of chicken intestines, were a more honest form of hustler.  I declare QM to be nothing more than an elaborate hoax meant to keep brainy math dudes in a constant supply of nubile and gullible undergrads.

[Nephew Twiddleton]

At least the scientists in the past who made their discoveries in the patterns made out of chicken intestines, were a more honest form of hustler.  I declare QM to be nothing more than an elaborate hoax meant to keep brainy math dudes in a constant supply of nubile and gullible undergrads.

You might be on to something there!

[Bruno]

Is the entanglement indefinite or do they become disentangled at some point?

Jesus, I've seen the future - we get a fuckton of these entangled qbits and then we break them up and put them in seperate routers and then we mould even more of them into a controller and the rest into the console ... BAM ... You got no input lag and no ping in your online game

QUANTUM GAMING WILL BE FUCKING AWESOME!

I think it would be safe to say that such an application would be more likely than teleporting or interstellar travel

I've thought the same thing, but my understanding is that this still does not make it possible to transfer information in less time than it would take for the information to travel the same distance at the speed of light.

This always leaves me with 4 basic unanswered questions:

1.)Wut?
2.)Why?
3.)Why not?
4.)Huh?

[P3nT4gR4m]

Is the entanglement indefinite or do they become disentangled at some point?

Jesus, I've seen the future - we get a fuckton of these entangled qbits and then we break them up and put them in seperate routers and then we mould even more of them into a controller and the rest into the console ... BAM ... You got no input lag and no ping in your online game

QUANTUM GAMING WILL BE FUCKING AWESOME!

I think it would be safe to say that such an application would be more likely than teleporting or interstellar travel

I've thought the same thing, but my understanding is that this still does not make it possible to transfer information in less time than it would take for the information to travel the same distance at the speed of light.

This always leaves me with 4 basic unanswered questions:

1.)Wut?
2.)Why?
3.)Why not?
4.)Huh?

I'm pretty sure no 3 can be answered with the aid of a microscopic cat and two slits

[Bruno]

Is the entanglement indefinite or do they become disentangled at some point?

Jesus, I've seen the future - we get a fuckton of these entangled qbits and then we break them up and put them in seperate routers and then we mould even more of them into a controller and the rest into the console ... BAM ... You got no input lag and no ping in your online game

QUANTUM GAMING WILL BE FUCKING AWESOME!

I think it would be safe to say that such an application would be more likely than teleporting or interstellar travel

I've thought the same thing, but my understanding is that this still does not make it possible to transfer information in less time than it would take for the information to travel the same distance at the speed of light.

This always leaves me with 4 basic unanswered questions:

1.)Wut?
2.)Why?
3.)Why not?
4.)Huh?

I'm pretty sure no 3 can be answered with the aid of a microscopic cat and two slits

The results of this experiment have already been observed at the macroscopic scale:

http://www.youtube.com/watch?v=f_tSSn22-FI
http://www.youtube.com/watch?v=3ID149JSVkU&feature=related

[Bebek Sincap Ratatosk]

Is the entanglement indefinite or do they become disentangled at some point?

Jesus, I've seen the future - we get a fuckton of these entangled qbits and then we break them up and put them in seperate routers and then we mould even more of them into a controller and the rest into the console ... BAM ... You got no input lag and no ping in your online game

QUANTUM GAMING WILL BE FUCKING AWESOME!

I think it would be safe to say that such an application would be more likely than teleporting or interstellar travel

I've thought the same thing, but my understanding is that this still does not make it possible to transfer information in less time than it would take for the information to travel the same distance at the speed of light.

Quantum Encryption systems, at this moment can transmit information (the encryption key value = the 'state' of X number of entangled qbits) faster than the speed of light.

Its a limited application but the 'spooky action at a distance' somehow breaks the rules model.

[Igor]

While the effects of the entanglement do appear to be instantaneous, you cannot actually transmit information with them.

Unfortunately, I seem to have forgotten the details as to why this is. I think it was something to do with having to compare the results at both ends before you can derive the information content. So you need a classical information channel as well.

This means you can have the security of a Quantum Entanglement-based cryptography system, but not the speed.

Edit: Actually, this bit on the talk page of the wikipedia article explains it better:

http://en.wikipedia.org/wiki/Talk:Quantum_entanglement#Quantum_Entanglement_not_violating_speed_of_light

[Bebek Sincap Ratatosk]

While the effects of the entanglement do appear to be instantaneous, you cannot actually transmit information with them.

Unfortunately, I seem to have forgotten the details as to why this is. I think it was something to do with having to compare the results at both ends before you can derive the information content. So you need a classical information channel as well.

This means you can have the security of a Quantum Entanglement-based cryptography system, but not the speed.

Edit: Actually, this bit on the talk page of the wikipedia article explains it better:

http://en.wikipedia.org/wiki/Talk:Quantum_entanglement#Quantum_Entanglement_not_violating_speed_of_light

Hrmmm...It seems the argument is that since measuring requires our POV, we can't 'get' the information faster than light... so information doesn't travel faster than light. The entanglement 'state change' (according to the math) happens faster than light, but since we can't measure it faster than light then information wasn't really transferred FTL?

[Igor]

Yeees, that sounds about right.

It's annoying, the way the universe has all this cool stuff going on, but whenever you try make it do something useful it disappears.
Almost as bad as the Cosmic Censorship Hypothesis, or the Chronology Protection Conjecture! 

[Nephew Twiddleton]

Yeees, that sounds about right.

It's annoying, the way the universe has all this cool stuff going on, but whenever you try make it do something useful it disappears.
Almost as bad as the Cosmic Censorship Hypothesis, or the Chronology Protection Conjecture! 

Well, I suppose it could still be useful. If I got the gist of it, the information can't travel faster than the speed of light because the particle in question (in this example a photon) can't go faster than that. Can't do shit with it now, but say if you were able to have a conglomeration of particles in some sort of analog to a radio on Earth and the same on Pluto. The particles in one would be entagled with the particles in the other and stabilized so they don't go flying off somewhere else. You could then send a message to Pluto instantaneously instead of a broadcast that would take 5 hours.

Don't ask me how this is doable. I'm just thinking shit up without a strong understanding of the subject. Naturally the radio would have to get to Pluto first in order for it to be useful. But if we can figure out how to do this sort of thing it might be useful in deep space probes.

[Bebek Sincap Ratatosk]

So what happens at a distance between qbits measured in Light Years? Obviously the observation is still slower than the speed of light, but not by 'years'... or would it be?

[Igor]

Well, I suppose it could still be useful. If I got the gist of it, the information can't travel faster than the speed of light because the particle in question (in this example a photon) can't go faster than that. Can't do shit with it now, but say if you were able to have a conglomeration of particles in some sort of analog to a radio on Earth and the same on Pluto. The particles in one would be entagled with the particles in the other and stabilized so they don't go flying off somewhere else. You could then send a message to Pluto instantaneously instead of a broadcast that would take 5 hours.

That won't work. The only time information is passed between the two particles is when they are "set up" on Pluto and Earth. Once they're in place, no more can go through. It's the fact of their being set up that is the information, in a way.

You really can't get around the speed of light.


Rat, if I understand you correctly; there isn't really much difference in the case where the particles are kilometres apart and when they're light years apart. You have to use the classical channel in both cases to get the information out. In the case of lightyears, it'll just take years instead of minutes.

Easier to use radio waves, really. They're as fast as you can get. The entanglement thing is really only useful for encryption.

[Bebek Sincap Ratatosk]

Well, I suppose it could still be useful. If I got the gist of it, the information can't travel faster than the speed of light because the particle in question (in this example a photon) can't go faster than that. Can't do shit with it now, but say if you were able to have a conglomeration of particles in some sort of analog to a radio on Earth and the same on Pluto. The particles in one would be entagled with the particles in the other and stabilized so they don't go flying off somewhere else. You could then send a message to Pluto instantaneously instead of a broadcast that would take 5 hours.

That won't work. The only time information is passed between the two particles is when they are "set up" on Pluto and Earth. Once they're in place, no more can go through. It's the fact of their being set up that is the information, in a way.

You really can't get around the speed of light.


Rat, if I understand you correctly; there isn't really much difference in the case where the particles are kilometres apart and when they're light years apart. You have to use the classical channel in both cases to get the information out. In the case of lightyears, it'll just take years instead of minutes.

Easier to use radio waves, really. They're as fast as you can get. The entanglement thing is really only useful for encryption.

Yep, after reading some more I see what they're saying.

It's not 'technically' information, because its simply either/or.  That is I can have quantum Encryption Key A 10 light years from Quantum Encryption key B... If I change the qbits in A, it will change the qbits in B FTL... but to get the encrypted message from A to B it will still take 10 light years.

Even for something like Paul Revere of the Quantum Kind, we'd have to communicate "Spin Up if by Land and Spin down if by sea" in some normal fashion, even if the entanglement change happened FTL.

?