Quantum Entanglement

[losfomot]

but it will 'interact', you seem to be underestimating what breaks the bond, the bond is very weak, so weak that you can't even measure it without breaking the bond, you also cant greatly adjust the properties of the atom, otherwise the bond is also borken.

 

I understand this, I still think it would work.

 

space is not a pure or real vacum, there are atoms floating around in space, additionally there are lots of photons, i.e. those emitted from stars.

 

I understand this as well, but the 'atoms floating around in space' would be negligible compared to the atoms floating around in a lab on Earth (where they have succesfully 'teleported' the state of a photon) which is why I pointed out that "It would be far less likely to interact with something there [in space] than travelling even a short distance in a lab"

 

Of course they may have done these entanglement experiments in a vacuum situation, I don't know.

 

you cant fully control entagle atoms as this will break the bond.

i'm guessing' date=' but it is possible that only certain quantum things can be controlled, such as the polerisation [for photons'] and not the actual course.

 

I never suggested "control" of the entangled atoms (and actually I was talking about photons) You brought the word 'control' into this discussion and I used in a way that I thought you were using it, but I see now that I was wrong. I only talked about changing the polarization of the photons.

 

it would be simpler to shoot photons at mars from a station on earth. we would control it from earth, as a man made machine, the shoot-photons-at-mars-machine would be controlled by us.

 

Yes, but that would be light speed communication, and the whole point of my 'setup' was to show a way to use entangled photons as a source of 'Faster Than Light' (FTL) communication.

[5614]

i seemed to misunderstand your meaning of 'control' appologies.

 

you would have to ask swansont or someone else whether you can adjust the polerisation of photons and not break the entagle bond, as im not sure, most things to break the bond though, i know more about quantum teleportation that entaglement.

 

you cant use photons in a FTL communication because photons can travel FTL, indeed nothing can travel faster than light, thus making all FTL communication hyper-thetical and so far, as far as humands are concerned totaly impossible.

 

with your idea, when the photon from the "space station" comes down to earth, it would hit something and be absorbed, you could not contain the photon and then change it, it is very hard to contain a photon, only TIR [total internal reflection] can be used, but i dont know how accurate your photon shooter would be, so we couldnt single out your photon and 'catch' it.

 

i think your idea is impractical and wouldnt work as a FTL communication method, mainly because photons work at C, FTL is faster than C. [other reasons are listed above]

[losfomot]

you would have to ask swansont or someone else whether you can adjust the polerisation of photons and not break the entagle bond, as im not sure, most things to break the bond though, i know more about quantum teleportation that entaglement.

 

I would love to have Swansont or anyone else knowledgable in this area to comment on my proposed 'setup'. (I hope they do it soon, cause I'm starting to bang my head against the wall)

 

Also, entanglement is the basis for quantum teleportation.

 

you cant use photons in a FTL communication because photons can travel FTL, indeed nothing can travel faster than light, thus making all FTL communication hyper-thetical and so far, as far as humands are concerned totaly impossible.

 

your 'quantum teleportation' is something (via entanglement) that is supposed to happen instantly . Instantly is Faster than Light. I am merely proposing a way to take advantage of this effect.

[5614]

if swansont was here he'd beam with proud coz of your first part, and then not reply for your second.

i know entaglement is the basis for quantum teleportation, that is why i know what entaglement is.

quantum teleportation is not instant it works at C, read the last 5 pages, its there somewhere, probably near the end.

 

it is possible i am wrong about the entaglement, but i am almost certain that your idea is impractical, even if theoretically it does work.

[see post #102]

[swansont]

Imagine this setup:

 

A photon emitter/entangler positioned between the Earth and Mars (slightly closer to the Earth). This machine splits photons (creates entangled photons) and sends one beam of the pair toward a predetermined position on Earth and its sister beam toward a polarimeter on Mars. Lets say these entangled photons were all linearly polarized.

 

So Mars' polarimeter is receiving a constant stream of linearly polarized photons.

 

We on Earth decide to change the polarization state of select portions of the photon beam aimed at our planet to circularly polarized. To keep things simple' date=' let's say in a morse code pattern.

 

Would someone on Mars, looking at the polarimeter readings IMMEDIATELY know what it is we are communicating to them.

 

Would this not be FTL communication? Or is my whole scheme misinformed.[/quote']

 

Measuring, or changing how you measure the photons on Earth will not change the state of the photons on Mars. That's not how it works. The information is encoded in the polarization, and the encoder has to transmit his encoding scheme, via some classical channel, which is limited by c.

[losfomot]

Measuring, or changing how you measure the photons on Earth will not change the state of the photons on Mars. That's not how it works. The information is encoded in the polarization, and the encoder has to transmit his encoding scheme, via some classical channel, which is limited by c.

 

 

"I see," lied the blind man.

 

So what use is quantum teleportation then? It will never be used to "teleport" objects or humans, and it can't even transmit information faster than what we can already do.

 

And what is with all those articles that predicted that quantum teleporting would lead to Faster than Light communication? Did we just recently figure out that this is not possible? Or were they all spouting BS right from the beginning.

[swansont]

So what use is quantum teleportation then? It will never be used to "teleport" objects or humans' date=' and it can't even transmit information faster than what we can already do.

 

And what is with all those articles that predicted that quantum teleporting would lead to Faster than Light communication? Did we just recently figure out that this is not possible? Or were they all spouting BS right from the beginning.[/quote']

 

It's useful because it can convey information with higher fidelity than a classical method. Think speed of computation rather than speed of transmission.

 

Any article that predicted FTL was probably written by a journalist that didn't understand the science (which, in my experience, is the majority) AFAIK No reputable scientist was predicting that.

[5614]

yub yub swansont,

 

quantum teleportation only has uses in quantum computing [at the moment], different polorisations could represent 1 or 0, which is binary, as used by computers at the moment.

 

you have [sadly, as many do] fallen into the trap of media explaining science. at the moment FTL anything is impossible, its all theoreticall, to have FTL would be breaking the laws of physics, which is why it seems exciting and the media often use it wrongly to make things seem exciting and sell.

[swansont]

you have [sadly, as many do'] fallen into the trap of media explaining science. at the moment FTL anything is impossible, its all theoreticall, to have FTL would be breaking the laws of physics, which is why it seems exciting and the media often use it wrongly to make things seem exciting and sell.

 

a. I fail to see how I have "fallen into the trap"

 

b. FTL is not theoretical. There is no theory that allows FTL travel of matter or information.

 

There is, however, hypothesis, conjecture and wishful thinking, and, of course, science fiction.

[5614]

NO NO NO, not you, losfomot fell for the trap of beleiving the media.

 

FTL is no possible, so i said it was theoretical, although this is bad wording. what i meant is that as its not possible, but heard of, i called it theoretical, bad use of the word, soz.

theoretical as in, in theory, its an idea which people hope to exploit and make useful and possible.

[but indeed bad wording on my behalf.]

[5614]

what kinda stuff is needed for quantum entaglement and/or quantum teleportation, im guessing you cant do it at home, but all the same, if this kinda stuff needs to fit inside a computer then it would be interesting if anyone knew?

[swansont]

what kinda stuff is needed for quantum entaglement and/or quantum teleportation, im guessing you cant do it at home, but all the same, if this kinda stuff needs to fit inside a computer then it would be interesting if anyone knew?

 

Lasers, spectoscopy setups for frequency locking, electronics and optics (lenses, polarizing beamsplitters, waveplates, fibers)

 

Here is one expertimental setup. Needless to say, it has not yet been miniaturized to the point of a computer yet.

 

Howver, it's easy to show that things can get smaller for similar setups.

[5614]

woa, thats big!

 

how do polarizing beamsplitters work?

i can guess what they do, but how?

 

the rest of the apparatus is pretty obvious.

[swansont]

how do polarizing beamsplitters work?

i can guess what they do' date=' but how?

[/quote']

 

You attach two prisms, with an index such that their connection is at brewster's angle, so the horizontal polarization orientation cannot be reflected. The interface is also antireflection coated for the target wavelength to maximize the reflection of the vertical polarization and transmission of the horizontal.

[5614]

i think that realsitically it is quite likely that it will get smaller soon.

[5614]

there's been a lot of talk on quantum teleportation in this thread, i was wondering if we could talk a bit about quantum entaglement now!

 

how's it work?

what do you need to do it?

does it actually have any practical uses other than quantum entaglement?

[NSX]

Well, I don't have the answers to you questions 5614, but I've got some of my own.

 

...and then change it, nothing happens to the other particle, because they are no longer entangled.

 

Step 3: One ion from the pair - in this case B - is entangled with A and both are measured

Step 4: The result of the measurement is sent to ion C and the tranformation implemented

 

I'm a bit lost from step 3 --> 4. How is the result of the measurement sent to ion C? Or is that the nature of entanglement?

[swansont]

I'm a bit lost from step 3 --> 4. How is the result of the measurement sent to ion C? Or is that the nature of entanglement?

 

The measurement result can be sent any way you want - digital signal along an optical fiber; carrier pigeon. It's because this communication is necessary that means that no information exceeds c. The entanglement is the "tie" between the two original particles.

[5614]

The measurement result can be sent any way you want - digital signal along an optical fiber; carrier pigeon. It's because this communication is necessary that means that no information exceeds c. The entanglement is the "tie" between the two original particles.

 

maybe no one else found this, but when i first read it i thoght that might have been referring to ion C. just to clarify he means c (as in the speed of light).

 

and once the measurement (presumably of the spin of the ion) is sent to ion C, how does ion C recieve that? like if you just shoot data waves (e.g. radio waves) at an atom it wont interact, but yet in this case it does, so why does ion C recieve and 'appl'y this information to itself?

or is it easier just to say this is what entaglement is!?

[NSX]

... once the measurement (presumably of the spin of the ion) is sent to ion C' date=' how does ion C recieve that? like if you just shoot data waves (e.g. radio waves) at an atom it wont interact, but yet in this case it does, so why does ion C recieve and 'appl'y this information to itself?

or is it easier just to say this is what entaglement is!?[/quote']

 

That's my predicament as well.

 

What is it in the measurement from one that changes the other?

Or is that the weirdness about entanglement?

[swansont]

What is it in the measurement from one that changes the other?

Or is that the weirdness about entanglement?

 

The measurement of one doesn't change the other. They were both in indeterminate states. But since they were entangled, once you measure one (and know which state it's in) you know what state the other was in.

[NSX]

ah...touché

 

But why is the state of ion A lost then?

[swansont]

ah...touché

 

But why is the state of ion A lost then?

 

The state isn't "lost," the entanglement is. i.e. once you've measured A's state, you can do whatever you like to it (including preserving its state) and it won't affect the other atom/ion at all. And the same goes for B - any subsequent measurement on it does not affect A.

[5614]

two questions:

 

1) NSX slightly changed my original question:

The measurement of one doesn't change the other. They were both in indeterminate states. But since they were entangled, once you measure one (and know which state it's in) you know what state the other was in.

if they both start off as indeterminate states, then how when you measure one do you know the others (after all they were in indeterminate states before they were measured) or is it the measuring effect which makes them the same state?

 

once you've measured A's state, you can do whatever you like to it (including preserving its state) and it won't affect the other atom/ion at all.

so is that implying that before you've measured the state you can change one of the ions states and the other one will change too? - just you wont notice the change because you wont have measured it?

[swansont]

two questions:

 

1) NSX slightly changed my original question:

 

if they both start off as indeterminate states' date=' then how when you measure one do you know the others (after all they were in indeterminate states before they were measured) or is it the measuring effect which makes them the same state?[/quote']

The individual states are unknown, but the particles are entangled somehow. e.g. they had zero total spin angular momentum. So if one is spin up, the other has to be spin down. You just don't know which is which until you measure. But then you know both.

 

so is that implying that before you've measured the state you can change one of the ions states and the other one will change too? - just you wont notice the change because you wont have measured it?

 

No. Any interaction breaks the entanglement.