Quantum Entanglement

[Aeschylus]

obviously post is a bit unrealistic' date=' but looking into the future.

 

thinking of using quantum teleportation/entaglement in quantum computing, how could you transport the data?

 

my thought, as you have said, lasers are used in experiments, so i say, in theory could you use some kind of radio waves, and thus send the info throug satelites, and consequently around the world?[/quote']

 

The communications channel isn't important, but there are parctical diffculties involved with distances as you must make sure th entangled particles remain in a pure state.

[5614]

The communications channel isn't important, but there are parctical diffculties involved with distances as you must make sure th entangled particles remain in a pure state.

 

the com chanel is important, if we want to involved this in long distance speed of light data transfer, in quantum computing, so i ask again:

 

could radio waves and satelites be used to carry such data,

and

What exactly, are the actualy difficulties in distances [why wouldnt the entagled particles remain in a pure state?]

[Aeschylus]

the com chanel is important' date=' if we want to involved this in long distance speed of light data transfer, in quantum computing, so i ask again:

 

could radio waves and satelites be used to carry such data,

and

What exactly, are the actualy difficulties in distances [why wouldnt the entagled particles remain in a pure state?']

 

Yes, I've said sevral times that the communications channel isn't importnt bar any practical difficulties it may present, so yes radio wave scould be used to carry this data.

 

If one of your particles ineracts with another particle it can destroy the experiment, loomk at the short distances entanlglemnt experiments are usually done at, tho' I believe one was performed over a distace of a few km recently.

[fuhrerkeebs]

no' date=' but presumably, this is the quickest way of doing so, so is it also the most common, and probably, when this science advances some more, the most common, or practical way of doing so, due to its speed?

 

also, does this impose a distance limit of how far away you can teleport things?

[ie. the laser would have to be able to reach that spot, so a straight line, unless there are mirros / satelites.']

 

also could there be data loss at long distances?

 

Using a laser is no faster than flicking a light switch on and off for morse code. Light always travels at c, no matter if it's a laser or just the light from your TV.

 

And there is always data loss as a result of noise (the information noise, not the sound noise) and other random occurences, and because of entropy (The information entropy, not the thermodynamics entropy--although they are similar). But the data loss can usually be recovered using error correcting codes...I don't know if you know it or not, but it's all basic information theory.

[5614]

Using a laser is no faster than flicking a light switch on and off for morse code. Light always travels at c, no matter if it's a laser or just the light from your TV.

 

yeah, obviously, and it just as quick as using radio waves, or even gamma rays! [that is, the same speed in a vacum] not in air, although the speed is almost identical it is not actually identical! im sure you know what i mean, [different colour lights travel at different speeds in air, not in a vacum though]

 

And there is always data loss as a result of noise (the information noise, not the sound noise) and other random occurences, and because of entropy (The information entropy, not the thermodynamics entropy--although they are similar). But the data loss can usually be recovered using error correcting codes...I don't know if you know it or not, but it's all basic information theory.

 

i guessed there would be data loss, i also guessed that the solution would be using error correcting codes.

[5614]

one sec, here's a basic question about quantum teleportation which i just wanna make sure ive got right... if you entagle say a carbon atom and a oxygen atom then only the properties of the atoms become similar, but the carbon doesnt turn into oxygen or vice versa, and in quantum teleportation you are ONLY teleporting the properties, so if you teleported the properties of a carbon atom onto the properties of an oxygen atom, the oxgen would NOT turn into carbon would it? it's just the spin and stuff, the properties which would become similar?

 

im confused, quantum teleportation is only teleporting the properties right? or the atom itself as well?

[swansont]

im confused, quantum teleportation is only teleporting the properties right? or the atom itself as well?

 

Properties. The atom is not physically teleported anywhere.

[5614]

ok, good good, thought so, just i was talking to someone, and they thought something, and then i thought something, and then we both just got all confused!

 

but here's a question i dont know the full answer to:

 

what does 'properties' include?

 

obviously the spin of the atom, but what else?

[Thales]

Properties. Mass, momentum, charge, spin, orientation...

 

If the properties can be recorded and different atoms instilled with these properties could this be considered 'copying' atoms?

 

The reason I ask relates to 'teleportation'. If the ability ever existed to 'teleport' people, wouldn't it also hold you could make an exact copy of yourself, same age, same thoughts etc. Now that would be a head f*#k and a half, more so than cloning.

[5614]

Properties. Mass[/b'], momentum, charge, spin, orientation...

 

if you are only teleporting the properties, how can you change the mass of the atom?

[Thales]

It is a property of the atom. It is information needed to recreate the atom completely. If you don't know what the mass of the original atom is you could easily install the properties on the wrong element.

[5614]

but the mass of a carbon atom is different to a oxygen atom, if you were entagling carbon with oxygen, then there would be a problem with which mass the oxygen would then have, because you can't add or remove mass from it... so what would happen?

[swansont]

Properties. Mass' date=' momentum, charge, spin, orientation...

[/quote']

 

Do you have any references that discuss "teleporting" any property other than spin or polarization?

[Thales]

No, I was talking hypothetically.

[5614]

Do you have any references that discuss "teleporting" any property other than spin or polarization?

 

so quantum teleportation only teleports the properties; spin and polarization?

[swansont]

so quantum teleportation only teleports the properties; spin and polarization?

 

Right. Spin for atoms or polarization for photons.

 

edit to add: it might be possible to also teleport the energy state of the atom; there are ways to "shelve" the electron into a metastable state.

 

But the bottom line is that it's got to be a state measurable by some QM measurement. Mass and charge don't qualify.

[Severian]

What makes you think mass and charge aren't QM observables?

[swansont]

What makes you think mass and charge aren't QM observables?

 

I didn't say they weren't. I said that you don't need a QM measurement to measure them. Classical physics works just fine. The whole lever of teleportation, as I understand it, is the increased fidelity over classical measurements. So it has to use something that you don't measure classically.

[Severian]

I didn't say they weren't. I said that you don't need a QM measurement to measure them. Classical physics works just fine. The whole lever of teleportation, as I understand it, is the increased fidelity over classical measurements. So it has to use something that you don't measure classically.

 

I am not sure in what sense you mean this. Mass and charge do need to be measured quantum mechanically. The masses of particles even have quantum corrections associated with them. Charge is the coupling of a particle to the U(1) gauge boson the photon, which is also definietly quantum mechanical in nature.

 

In fact, the mass operator is [math]\hat P^2[/math] where [math]\hat P[/math] is the 4-momentum operator, so if you regard momentum as being QM in nature, so is mass - [math]\hat P^2[/math] does not commute with the position-space operator for example. (That depends on your definition of 'mass' of course.)

 

As for charge, imagine producing an electron-positron pair in a collision, but not measuring anything about them other than their momentum - you would not know which is + and which -. But when you measure one, you know the other (exactly analagous to the usual example of spin).

[swansont]

I am not sure in what sense you mean this. Mass and charge do need to be measured quantum mechanically.

 

There is nothing inherently quantum mechanical about a mass spectrometer measurement. All of the physics of doing the measurement is classical.

[losfomot]

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, 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.

[5614]

i think that after that kinda distances the entagle link would become lost as for the entagle link to remain you must make sure th entangled particles remain in a pure state.

 

also what you are suggesting, it would be easier to just send packets of photons to the mars from earth from a controllable light source, you dont need entaglement and stuff like that just to send possible controllable photons to mars.

[losfomot]

i think that after that kinda distances the entagle link would become lost as for the entagle link to remain you must make sure th entangled particles remain in a pure state.

 

First off, the entanglement is supposed to last forever (or at least until interaction). Second, what better place to 'remain in a pure state' than in the vacuum of space? It would be far less likely to interact with something there than travelling even a short distance in a lab.

 

also what you are suggesting, it would be easier to just send packets of photons to the mars from earth from a controllable light source, you dont need entaglement and stuff like that just to send possible controllable photons to mars.

 

You don't? ... I thought, to be 'controllable' (so to speak) they HAD to be entangled in the first place. How do you 'control' photons that you sent to Mars without entanglement?

[losfomot]

Sorry, I think I know where (some of) the confusion came from... in my 'setup' above, I had originally suggested putting the photon emitter/entangler between the Moon and Earth. It was supposed to be between Mars and the Earth, and I have now corrected it.

[5614]

First off, the entanglement is supposed to last forever (or at least until interaction). Second, what better place to 'remain in a pure state' than in the vacuum of space? It would be far less likely to interact with something there than travelling even a short distance in a lab.

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.

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.

 

You don't? ... I thought, to be 'controllable' (so to speak) they HAD to be entangled in the first place. How do you 'control' photons that you sent to Mars without entanglement?

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

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

 

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.