Quantum Entanglement ?

[interested]

Can any one explain how quantum entanglement works, and the limits of what is achievable through quantum entanglement.

[J.C.MacSwell]

4 hours ago, interested said:

Can any one explain how quantum entanglement works, and the limits of what is achievable through quantum entanglement.

Wiki can get you started.

 

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

[Handy andy]

On ‎30‎/‎07‎/‎2017 at 6:18 PM, interested said:

Can any one explain how quantum entanglement works, and the limits of what is achievable through quantum entanglement.

here are some more interesting links

https://phys.org/news/2017-07-probability-quantum-world-local-realism.html?utm_source=nwletter&utm_medium=email&utm_campaign=daily-nwletter

Also Modreds thread on "what space is made off" is incredibly interesting, and broaches on entanglement.

 

[swansont]

2 hours ago, Handy andy said:

 Also Modreds thread on "what space is made off" is incredibly interesting, and broaches on entanglement.

We have several threads that discuss entanglement and quantum teleportation as the topic of discussion, rather than as a tangent.

[interested]

3 hours ago, swansont said:

We have several threads that discuss entanglement and quantum teleportation as the topic of discussion, rather than as a tangent.

Are you serious about teleportation?. 

The links were interesting, I read bits on Wikipedia before, but don't think I found that link.

I have some questions remaining,

Is information transmitted instantly beyond the speed of light between the entangled particles? is the distance between entangled particles not the same in the quantum world.

once particles are entangled how long can it last.? 

Mordreds thread was interesting, but a bit over my head in places, especially towards the end.

Thankyou for the links.

Edited August 1, 2017 by interested

[swansont]

19 minutes ago, interested said:

Are you serious about teleportation?. 

The links were interesting, I read bits on Wikipedia before, but don't think I found that link.

I have some questions remaining,

Is information transmitted instantly beyond the speed of light between the entangled particles? is the distance between entangled particles not the same in the quantum world.

once particles are entangled how long can it last.? 

Mordreds thread was interesting, but a bit over my head in places, especially towards the end.

Thankyou for the links.

Teleportation is information transfer, not like Star Trek, where matter is teleported and is fictional.

There is no evidence of information being transferred. Whatever effect is happening, it is instantaneous (as far as we can tell), but there is no way to exploit this to communicate with anyone. Think of this example: you flip a coin. As soon as you see what one side it (heads) you instantly know what the other side is (tails). Does that require the transfer of information? Now imagine the coin is 1 light-second wide.  

Entanglement lasts until some interaction removes it, called decoherence. Anything that measures the state that's entangled removes it. 

[interested]

1 hour ago, swansont said:

Teleportation is information transfer, not like Star Trek, where matter is teleported and is fictional.

There is no evidence of information being transferred. Whatever effect is happening, it is instantaneous (as far as we can tell), but there is no way to exploit this to communicate with anyone. Think of this example: you flip a coin. As soon as you see what one side it (heads) you instantly know what the other side is (tails). Does that require the transfer of information? Now imagine the coin is 1 light-second wide.  

Entanglement lasts until some interaction removes it, called decoherence. Anything that measures the state that's entangled removes it. 

Thankyou for the clarification and answers. I did a quick search for clarification, and found these links for anyone interested.

http://news.bbc.co.uk/1/hi/sci/tech/3811785.stm

https://en.wikipedia.org/wiki/Quantum_decoherence

Thanks

[Handy andy]

I saw this and thought of you. China leads the way, maybe!

https://phys.org/news/2017-08-chinese-team-quantum-keys-ground.html?utm_source=nwletter&utm_medium=email&utm_campaign=daily-nwletter

 

[interested]

On ‎12‎/‎08‎/‎2017 at 10:09 AM, Handy andy said:

I saw this and thought of you. China leads the way, maybe!

https://phys.org/news/2017-08-chinese-team-quantum-keys-ground.html?utm_source=nwletter&utm_medium=email&utm_campaign=daily-nwletter

 

Thanks Handy andy BUT What does "China leads the way, maybe!" mean, do you or anyone else doubt the Chinese claims.

I posted on the expanding space thread ref the speed of action in quantum entanglement and may have misunderstood the references in the links above using the word "instantaneous" After a little use of google I came up with the following.

"Quantum entanglement, one of the odder aspects of quantum theory, links the properties of particles even when they are separated by large distances. When a property of one of a pair of entangled particles is measured, the other "immediately" settles down into a state compatible with that measurement. So how fast is "immediately"? According to research by Prof. Juan Yin and colleagues at the University of Science and Technology of China in Shanghai, the lower limit to the speed associated with entanglement dynamics – or "spooky action at a distance" – is at least 10,000 times faster than light."

http://newatlas.com/quantum-entanglement-speed-10000-faster-light/26587/

Is the above statement from the above link accurate? Could the speed of data transmission be between instant and 10,000 x faster than c? Is the jury still out?

Also is it likely that another dimension exists that the data is transmitted through, which connects the quantum entangled particles? 

[Strange]

40 minutes ago, interested said:

Is the above statement from the above link accurate? Could the speed of data transmission be between instant and 10,000 x faster than c? Is the jury still out?

It is accurate, apart from the implication that there is some sort of data transmission. Note that the 10,000 c is a lower limit. It is possible/likely that it is instantaneous. The point about an entangled system is that it is a single entity. So, in swansont's coin analogy, you wouldn't expect any delay between one side being heads and the other tails. They happen at the same time because they are a single thing.

Quote

Also is it likely that another dimension exists that the data is transmitted through, which connects the quantum entangled particles? 

That sounds like an attempt at a "hidden variables" explanation, which we know doesn't work. 

[Itoero]

6 hours ago, interested said:

Also is it likely that another dimension exists that the data is transmitted through, which connects the quantum entangled particles? 

You might want to have a look in ER=EPR.https://en.wikipedia.org/wiki/ER%3DEPR An ER bridge you can call a property of a hidden dimension.

[interested]

Thanks Strange for the clarification and Itoero for the link ref ER.

A worm hole connecting particle A to B, or the two particles even though they are seperated are the same particle, is almost religious. I see why Einstein said it was spooky action at a distance.

How many degrees of movement do entangled particles have, is it just rotational, or are there more degrees of freedom.

[Itoero]

54 minutes ago, interested said:

A worm hole connecting particle A to B, or the two particles even though they are seperated are the same particle, is almost religious. I see why Einstein said it was spooky action at a distance.

How many degrees of movement do entangled particles have, is it just rotational, or are there more degrees of freedom.

They don't behave as separate particles until you measure them, they are described by a wavefunction. The degree of freedom depends on the properties of the entangled particles..

[Mordred]

Good answer Itoero +1

[Handy andy]

On ‎13‎/‎08‎/‎2017 at 11:12 AM, interested said:

Thanks Handy andy BUT What does "China leads the way, maybe!" mean, do you or anyone else doubt the Chinese claims.

 

 

The Chinese claim to be the first to have done this, why believe them without more information? . Researchers need to raise funds, claiming to be the first is good publicity etc. 

I have a tendency to disbelieve and look for inconsistencies in arguments, rather than believing everything that is written. You will notice that quantum entanglement appears to violate special relativity. This might imply special relativity which is part of the standard model of physics is a little bit wrong, something you may get into trouble with the moderators for suggesting.

[Strange]

50 minutes ago, Handy andy said:

The Chinese claim to be the first to have done this, why believe them without more information? . Researchers need to raise funds, claiming to be the first is good publicity etc. 

Why believe they are first? Because no one else has claimed to do this.

Why believe they have done it at all? Well, one could review the published research or wait for others to do so.

Quote

You will notice that quantum entanglement appears to violate special relativity. 

No it doesn't. No information is communicated.

[interested]

28 minutes ago, Strange said:

It is accurate, apart from the implication that there is some sort of data transmission. Note that the 10,000 c is a lower limit. It is possible/likely that it is instantaneous. The point about an entangled system is that it is a single entity. So, in swansont's coin analogy, you wouldn't expect any delay between one side being heads and the other tails. They happen at the same time because they are a single thing.

No it doesn't. No information is communicated.

Can you expand on the above statements? Are you now contradicting your earlier post

Quantum computers using entanglement would seem to be pointless if no information can be stored, retrieved or manipulated.

[swansont]

40 minutes ago, interested said:

Can you expand on the above statements? Are you now contradicting your earlier post

Quantum computers using entanglement would seem to be pointless if no information can be stored, retrieved or manipulated.

No information is communicated faster than c. Nobody with knowledge of the physics has contradicted this.

The phenomenon is useful for quantum computation (for certain problems) because superposition can be exploited to store and process a lot of information, quickly.

[Strange]

41 minutes ago, interested said:

Can you expand on the above statements? Are you now contradicting your earlier post

Quantum computers using entanglement would seem to be pointless if no information can be stored, retrieved or manipulated.

A pair of entangled particles are effectively a single entity so, when an observation is made of one particle (e.g. measuring its spin) then the measurement is made of the whole system and so the spin of both particles is determined at that instant. (Note that in quantum theory, the spins are not just unknown until they are measured, they don't have a specific value until measured.)

From that moment, there are two separate particles with different spins. However, if Alice has one of he entangled particles and Bob has the other, there is no way that one of them can tell if the other has made a measurement of the spin (other than through traditional light-speed communication). So the measurement of one particle does not communicate any information to the observer of the other particle.

But an entangled pair of particles does/can carry information. I don't know anything much about how quantum computers work, but entangled particles are used in several other contexts. For example, measuring "which slit" a photon went through in a double-slit experiment without interacting with the particle that actually went through the slit - you measure an entangled partner and use that information to deduce which slit the other one went through.

[swansont]

2 hours ago, Handy andy said:

The Chinese claim to be the first to have done this, why believe them without more information? . Researchers need to raise funds, claiming to be the first is good publicity etc. 

They were the first to do this particular task, not the first to show entanglement or teleportation. It's incremental progress in an area that has shown several steps of incremental progress. Why not believe them? 

Quote

I have a tendency to disbelieve and look for inconsistencies in arguments, rather than believing everything that is written. You will notice that quantum entanglement appears to violate special relativity. This might imply special relativity which is part of the standard model of physics is a little bit wrong, something you may get into trouble with the moderators for suggesting.

People who actually understand the physics will notice that this is wrong. As Strange notes, no information is communicated faster than c. If you want to suggest that any part of mainstream physics is wrong you need to have evidence. Making the claims without evidence (and repeatedly making claims based on misunderstanding the physics compounds this) is what gets you in trouble. 'Not understanding the rules' is the common theme here.

[Itoero]

There is a form of information transmitted...the act of measuring. This is used in quantum key distribution to make super secure communication key's. The important and unique property of quantum key distribution is the ability of the two communicating users to detect the presence of any third party trying to gain knowledge of the key.https://en.wikipedia.org/wiki/Quantum_key_distribution

[Strange]

2 minutes ago, Itoero said:

There is a form of information transmitted...the act of measuring. This is used in quantum key distribution to make super secure communication key's. 

That information can only be transmitted (separately) at light speed or less.

[Phi for All]

!

Moderator Note

A hijack post and its replies have been split off to here. This is a mainstream section, and speculative science is neither wanted nor appreciated here.

 

[interested]

Thanks for the explanations. To summarise what I think may have been written above.

Entangled particles are thought to transmit information via a wormhole from points A to B separated by a distance x as a wave function. This information because it travels through a worm hole is close to instantaneous. The information can only be viewed at light speed, and therefore does not violate special relativity.

The information is destroyed or decoheres once viewed and so is secure. Until the information is viewed it is a paradox ie until you look at the result you don't know the answer.

Quantum keys are used to make data more secure, anyone with the key can access the data, anyone without the key can not and can be detected trying to gain access.

Is the above right or wrong?

How are particles entangled? Can particles separated by a distance be entangled ie what is the upper limit on separation of particles to entangle them? Does anyone have a good link on how entanglement is done and what the limits are on separation of particles.? Do entangled particles behave the same way as entangled photons used in computing?

22 hours ago, swansont said:

No information is communicated faster than c. Nobody with knowledge of the physics has contradicted this.

 

According to research by Prof. Juan Yin and colleagues at the University of Science and Technology of China in Shanghai, the lower limit to the speed associated with entanglement dynamics – or "spooky action at a distance" – is at least 10,000 times faster than light."

 

Edited August 16, 2017 by interested

[Strange]

1 minute ago, interested said:

Entangled particles are thought to transmit information via a wormhole

That is an extremely speculative concept that is just based on an apparent mathematical similarity. It is not yet established to be the case. The standard, and very simple, explanation is just that quantum effects are non-local (in both time and space).