Quantum teleportation of macroscopic objects

[hammertime]

I've started a couple of threads about this topic before, but those were a while ago, and I still have some nagging questions.

1.) If we wanted to quantum teleport something macroscopic, would scanning come into play? I thought that the whole point of QT was that you don't have to scan whatever it is you want to teleport. Would the only scanning take place before QT, in order to figure out the configurations and positions of the atoms so that a replica could be made at the destination (let's say the destination has stores of materials that they could use to make identical replicas)? Once the two objects are entangled, don't we just have to measure the quantum state of the object at the source and then send the result of the measurement to the destination? Wouldn't the entire object have one quantum state, as opposed to each atom having a state that must be measured?

2.) I understand that, in all of the experiments done so far in QT, the atoms were at close to absolute zero. For macroscopic objects to be quantum teleported, how low would the temperature have to be? Would you risk converting the object to a Bose-Einstein condensate, or in any other way fundamentally and irreversibly altering the object, by lowering it to a temperature suitable for QT?

3.) I once suggested that, if scanning was necessary, we could use nanobots that would infiltrate the object (if it was a human, they would go through the bloodstream and blood vessels), but was told that the energy required to scan all the atoms in such a short time frame would create a black hole. How so?

4.) This is kind of related to another thread I recently started, but if we wanted to entangle the two objects, would we have to entangle them atom-by-atom, or could we entangle the entire object? Would we have to keep the two objects close to each other and then send them apart?

 

[Chronos]

You would need to 'force' every atom of the macroscopic object into the same quantum state simultaneously. That would be difficult.

 

[DrChinese]

I've started a couple of threads about this topic before, but those were a while ago, and I still have some nagging questions.

1.) If we wanted to quantum teleport something macroscopic, would scanning come into play? I thought that the whole point of QT was that you don't have to scan whatever it is you want to teleport. Would the only scanning take place before QT, in order to figure out the configurations and positions of the atoms so that a replica could be made at the destination (let's say the destination has stores of materials that they could use to make identical replicas)? Once the two objects are entangled, don't we just have to measure the quantum state of the object at the source and then send the result of the measurement to the destination? Wouldn't the entire object have one quantum state, as opposed to each atom having a state that must be measured?

2.) I understand that, in all of the experiments done so far in QT, the atoms were at close to absolute zero. For macroscopic objects to be quantum teleported, how low would the temperature have to be? Would you risk converting the object to a Bose-Einstein condensate, or in any other way fundamentally and irreversibly altering the object, by lowering it to a temperature suitable for QT?

3.) I once suggested that, if scanning was necessary, we could use nanobots that would infiltrate the object (if it was a human, they would go through the bloodstream and blood vessels), but was told that the energy required to scan all the atoms in such a short time frame would create a black hole. How so?

4.) This is kind of related to another thread I recently started, but if we wanted to entangle the two objects, would we have to entangle them atom-by-atom, or could we entangle the entire object? Would we have to keep the two objects close to each other and then send them apart?

Scanning? Teleportation? Nanobots? This is sort of going Star Trek here. Most of this makes little scientific sense. Can you bring it back to a specific question about something which is not born from fiction? Thanks.

 

[Ryan_m_b]

I once suggested that, if scanning was necessary, we could use nanobots that would infiltrate the object (if it was a human, they would go through the bloodstream and blood vessels), but was told that the energy required to scan all the atoms in such a short time frame would create a black hole. How so?

*Sigh, as someone in the field of medical nanotechnology it https://www.physicsforums.com/blog.php?b=3179" their paper.

 

[xts]

*Sigh, as someone in the field of medical nanotechnology depresses me...

Welcome to the club! I am a bit farther from nano-tech, but I believe I got some insider's view on quantum engineering, and I may to say the same about all that hi-pitch excitation about teleportation, time-travelling, etc... Like this thread ;)

[ No, Hammertime! It is impossible to teleport macroscopic objects. It is impossible to teleport even single atom. What you may teleport is some quantum property of an object. And you may teleport only discrete properties - like spin, or excitation state of ion - but you can't teleport even simplest continuous property (like momentum). So forget about teleporting humans! Especially deep-frozen humans. ]

People really don't understand Anton Zeilinger's Schlagwort: Papers must be sexy.
Many of them think that covering their boring ideas with shining red lipstick of words like 'nano-' 'teleportation', and 'quantum' makes them sexy...

Calgonit Quantum - the unbeatable dishwasher tabs - http://www.finish.de/index.php

 

[Ryan_m_b]

Welcome to the club! I am a bit farther from nano-tech, but I believe I got some insider's view on quantum engineering, and I may to say the same about all that hi-pitch excitation about teleportation, time-travelling, etc... Like this thread ;)

People really don't understand Anton Zeilinger's Schlagwort: Papers must be sexy.
Many of them think that covering their boring ideas with shining red lipstick of words like 'nano-' 'teleportation', and 'quantum' make them sexy...

Calgonit Quantum - the unbeatable dishwasher tabs - http://www.finish.de/index.php

Grrr products like that grind my gears! I really like this article published in Nature by Andrew Moore. It's a little old now but the point still stands; with so many different research groups, science/engineering disciplines, pop-sci/sci-fi authors, NGOs, government departments and companies using the term "nanotechnology" there's a real danger that it's meaning will be completely lost on the public and it will become a useless word. I especially like this section...

“We need to quickly move away from the nanotechnology word and describe its applications,” he said, commenting on the possible regulation of nanotechnology in general, “it's a bit like saying we're going to regulate physics... or have a moratorium on chemistry.”

EDIT: I realize this may seem to be getting a bit off-topic so to make it more relevant:
hammertime I'd advise you to take a look at the topics discussed here in depth so that you can look towards getting a proper understanding of the sciences involved rather than a confused pop-sci and sci-fi understanding.

 

[MrDementao]

There is no need to scan the hole object. That is the point of quantum teleportation, you send your unknown quantum state to another person and the person is sure that is your state (with high fidelity).

However, you and your partner need to share a quantum channel - i.e, a quantum entangled state. In theory, if you can produce a macroscopic entangled state (called two-mode Schrodinger-cat states), you could teleport a macroscopic object. There are some experiments on this. Btw, it is possible to teleport an atom.

The problem with big objects for me would be in the measurement that you do. You have always to perform a joint measurement in the state you want to send and in the state of the channel, and this should be not very trivial for big objects - even in the simplest cases of quantum objects this is hard. Also, maybe the amount of classical information would scale brutally.

 

[DrChinese]

Btw, it is possible to teleport an atom.

Welcome to PhysicsForums, MrDementao!

You left off the words "state of" here, i.e. you can teleport a state rather than the actual atom. And I am a bit dubious about teleporting "the state" of an entire atom. Do you have any references so I can see what you are referring to specifically?

 

[xts]

you could teleport a macroscopic object. There are some experiments on this.

Any references? On teleportation of the object, not just it single (or few) discrete properties?
The whole state of atom had been teleported? Or its spin or excitation only?

Also, maybe the amount of classical information would scale brutally.

In case of continuous property (like position or momentum) - it would require infinite amount of information. Well, you may probably cut it off at Planck's scale. Then finite (but large) amount of information is sufficient...

 

[MrDementao]

Sorry:

http://futureblast.com/2011/04/first-teleportation-with-atoms/

This second one maybe is also an experiment on this, but I am not so sure:

http://www.nature.com/nature/journal/v396/n6706/full/396052a0.html

I am not a fan of NMR.

Hello, Dr Chinese, thanks!
I don't understand the word "actual atom". There are quantum states that we call "atom", I don't see what an actual atom should be. But let me think more, maybe I see the point.

 

[xts]

http://futureblast.com/2011/04/first-teleportation-with-atoms/:
scientists teleported the quantum state of one calcium atom [...] The quantum state includes the energy configuration of the atom and its electrons.

What about other properies? Spins? Atom momentum/position? Nucleus state?
We have just few discrete parameters, not the whole atom.

http://www.nature.com/nature/journal/v396/n6706/full/396052a0.html
To read this story in full you will need to login or make a payment

 

[DrChinese]

Sorry:

http://futureblast.com/2011/04/first-teleportation-with-atoms/

...

Hello, Dr Chinese, thanks!
I don't understand the word "actual atom". There are quantum states that we call "atom", I don't see what an actual atom should be. But let me think more, maybe I see the point.

This reference isn't really much (didn't even mention the paper's authors). Here is an "associated" reference from the same group of scientists a few years later:

http://arxiv.org/abs/0704.2027

I just want to caution readers about the use of the word "teleport". In general, using entanglement, a quantum state is moved from particle A to particle B. No actual force or matter is moved anywhere as a result of the process.

 

[MrDementao]

What about other properies? Spins? Atom momentum/position? Nucleus state?
We have just few discrete parameters, not the whole atom.

The properties are the same, since is the same quantum state. They teleported the state of the atom. There is not a difference between atom and quantum state of the atom. The state - wave function/density matrix - has all physical properties of the atom encoded. In this sense they indeed teleported the whole atom.

Maybe a better reference:
http://www.physics.utoronto.ca/~dfvj/Publications%20by%20Daniel%20F%20V%20James/3-Unrefereed_Publications/proc11_ICAPTeleportation.pdf

There are not so much actual experiments, but a lot of proposed schemes. I don't think this will be impossible. It is hard, but not impossible.

 

[DrChinese]

There is not a difference between atom and quantum state of the atom. The state - wave function/density matrix - has all physical properties of the atom encoded. In this sense they indeed teleported the whole atom.

I think it would be safe to say that there is a difference between the two, and certainly a difference in teleporting the two. Some of the issues will end up being semantical though.

Thanks for the other reference, that helps.

 

[xts]

There is not a difference between atom and quantum state of the atom.

I agree.
Just one comment. We never use the wave function of the atom. If you solve Schrödinger equation of Tritium atom at the class of QM, you solve the problem of point-like charge (electron) in a field of pointlike charge (nucleus). The wave function you use describe just a small part of atom's behaviour - its energetic states. It says nothing about electron spin.
You may go further on the way and include spin in more complicated calculations in more dimensional Hilbert space. But your tritium atom suddenly decays. You want cover this too? OK. Let's make all calculations to compute the wavefunction of the nucleus, and quarks within nucleons... All that constitute atom.

I believe you don't claim any of those experiments entangled not only energetic states of the electrons, but also nuclear ones?

Another issue is atom position. As long as you teleport single atom, it is preassumed, that new one is in different place than original one and constitutes its own reference frame. But as you want to teleport a system of two or more atoms, you must also reconstruct their relative positions (or rather wavefunction leading to their relative position). And here you fall into a problem of teleporting continuous variable, which require infinite information.

 

[MrDementao]

Yep, we would end going into the definition of what a quantum state is, or what an actual atom is*.

However, the teleportation scheme in any case is the teleportation of the quantum state, which possesses all the relevant physical properties of the atom.

(* it is hard for me to accept this distinction: What an actual atom has that is not described by its full quantum state?)

 

[MrDementao]

When you teleport the full quantum state it will have all the properties of the original one. And that is the gain in teleportation: you don't need to know which one is your state, you know that after the protocol the state in the other side will be your state. So you don't need to reconstruct your state, or measure its polarization or whatever. You just need to be able to do some Bell-like measurements and comunicate classically.

There is teleportation in continuous variables with photons. You don't need infinite amount of information to perform it.

As Dr Chinese said, maybe we have a semantic misunderstanding here.

 

[xts]

(* it is hard for me to accept this distinction: What an actual atom has that is not described by its full quantum state?)

I don't use this distinction.
I just say that experiments are done regarding limited-subset-of-full-state, rather than full-state and it seems to be impossible to do any teleportation (or other) experiment operating on the full state.
Photons have well defined full-state: spin, momentum/position, that's all. For atoms that is not so easy.

There is teleportation in continuous variables with photons. You don't need infinite amount of information to perform it.

Reference please!

When you teleport the full quantum state it will have all the properties of the original one. And that is the gain in teleportation: you don't need to know which one is your state,

But I must know what the Hilbert space describing this state is. And teleportation couples only subset of the full-state Hilbert space dimensions.

 

[hammertime]

This reference isn't really much (didn't even mention the paper's authors). Here is an "associated" reference from the same group of scientists a few years later:

http://arxiv.org/abs/0704.2027

I just want to caution readers about the use of the word "teleport". In general, using entanglement, a quantum state is moved from particle A to particle B. No actual force or matter is moved anywhere as a result of the process.

Yes, but consider the following. If we had, say, teleportation stations and at each station there were huge reserves of elements like carbon, hydrogen, oxygen, nitrogen, etc., we could then build a replica of the object whose state we want to teleport at the destination and then QT the state of the object at the source to the object at the destination. Wouldn't that work? That way, we would only need to send information about the position and state of the atoms, as opposed to the actual atoms themselves.

Yes, I know it's a lot of information to send, but there's no reason we can't send all the information in a certain amount of time. Hell, we could send that information by using a pair of entangled particles! Isn't that the currently expected use of QT? To send information super fast?

And the part where we determine the position of atoms in the object build the replica at the destination from the reserves of materials? That's where the nanobots come in.

 

[hammertime]

I agree.
Just one comment. We never use the wave function of the atom. If you solve Schrödinger equation of Tritium atom at the class of QM, you solve the problem of point-like charge (electron) in a field of pointlike charge (nucleus). The wave function you use describe just a small part of atom's behaviour - its energetic states. It says nothing about electron spin.
You may go further on the way and include spin in more complicated calculations in more dimensional Hilbert space. But your tritium atom suddenly decays. You want cover this too? OK. Let's make all calculations to compute the wavefunction of the nucleus, and quarks within nucleons... All that constitute atom.

I believe you don't claim any of those experiments entangled not only energetic states of the electrons, but also nuclear ones?

Another issue is atom position. As long as you teleport single atom, it is preassumed, that new one is in different place than original one and constitutes its own reference frame. But as you want to teleport a system of two or more atoms, you must also reconstruct their relative positions (or rather wavefunction leading to their relative position). And here you fall into a problem of teleporting continuous variable, which require infinite information.

Huh? Can you elaborate, please?

 

[MrDementao]

I don't use this distinction.
But I must know what the Hilbert space describing this state is. And teleportation couples only subset of the full-state Hilbert space dimensions.

You quantum system gives your Hilbert-space. That teleportation couples with subset of Hilbert-space... in terms of photons I think you teleport the full quantum state. If you can prepare a two-mode squeezes vacuum state and perform the bell-measurements, you teleport whichever state you want. You just need to be able to perform the right kind of measurement for teleportation.

Reference fo cont. variables telp.: http://arxiv.org/abs/0910.2713

and references in it.

 

[xts]

Thanks for reference!
Too long and too serious to respond at once. I'll read it and comment on Monday (I am leaving for weekend).

Of course, in terms of photons, the full quantum state is well defined and feasible (even easy) to access. But not for atoms including nuclei...

 

[hammertime]

Thanks for reference!
Too long and too serious to respond at once. I'll read it and comment on Monday (I am leaving for weekend).

Of course, in terms of photons, the full quantum state is well defined and feasible (even easy) to access. But not for atoms including nuclei...

Ah, so does that mean that we're technologically closer to what I'm talking about?

 

[xts]

No, Hammertime, we are not. Don't even dream about that.

 

[MrDementao]

Hammertime, I guess for atoms and "macroscopic" objects like molecules yes, but for a big macroscopic object like a key we are very very far. It seems that for increasing complexity of the object the number of resources used scales exponentially. Even if there is a way, maybe it is too costly.

 

[hammertime]

Scanning? Teleportation? Nanobots? This is sort of going Star Trek here. Most of this makes little scientific sense. Can you bring it back to a specific question about something which is not born from fiction? Thanks.

I don't see what's so outlandish about this. Can you explain? I've made a few suggestions. Could you please tell me what's wrong with them?

Remember, things like the internet, space travel, and supersonic flight were once science fiction, too.

 

[hammertime]

You would need to 'force' every atom of the macroscopic object into the same quantum state simultaneously. That would be difficult.

Isn't that done by simply lowering the temperature to a certain level? If not, how would one accomplish this?

 

[hammertime]

Welcome to the club! I am a bit farther from nano-tech, but I believe I got some insider's view on quantum engineering, and I may to say the same about all that hi-pitch excitation about teleportation, time-travelling, etc... Like this thread ;)

[ No, Hammertime! It is impossible to teleport macroscopic objects. It is impossible to teleport even single atom. What you may teleport is some quantum property of an object. And you may teleport only discrete properties - like spin, or excitation state of ion - but you can't teleport even simplest continuous property (like momentum). So forget about teleporting humans! Especially deep-frozen humans. ]

People really don't understand Anton Zeilinger's Schlagwort: Papers must be sexy.
Many of them think that covering their boring ideas with shining red lipstick of words like 'nano-' 'teleportation', and 'quantum' makes them sexy...

Calgonit Quantum - the unbeatable dishwasher tabs - http://www.finish.de/index.php

Well, as Mr. Dementao just showed us, we can, indeed, teleport continuous properties. So that's one more obstacle out of the way.

Besides, is there any reason in particular why we can't QT more than one property? All it takes is one brilliant scientist, right?

 

[hammertime]

There is no need to scan the hole object. That is the point of quantum teleportation, you send your unknown quantum state to another person and the person is sure that is your state (with high fidelity).

However, you and your partner need to share a quantum channel - i.e, a quantum entangled state. In theory, if you can produce a macroscopic entangled state (called two-mode Schrodinger-cat states), you could teleport a macroscopic object. There are some experiments on this. Btw, it is possible to teleport an atom.

The problem with big objects for me would be in the measurement that you do. You have always to perform a joint measurement in the state you want to send and in the state of the channel, and this should be not very trivial for big objects - even in the simplest cases of quantum objects this is hard. Also, maybe the amount of classical information would scale brutally.

I'm a bit confused about this. Isn't it just an issue of scaling up from what we're doing now? Couldn't sufficient technological and scientific advances lead us to do this?

 

[hammertime]

The properties are the same, since is the same quantum state. They teleported the state of the atom. There is not a difference between atom and quantum state of the atom. The state - wave function/density matrix - has all physical properties of the atom encoded. In this sense they indeed teleported the whole atom.

Maybe a better reference:
http://www.physics.utoronto.ca/~dfvj/Publications%20by%20Daniel%20F%20V%20James/3-Unrefereed_Publications/proc11_ICAPTeleportation.pdf

There are not so much actual experiments, but a lot of proposed schemes. I don't think this will be impossible. It is hard, but not impossible.

That's my point. So if teleporting the quantum state of an atom is the same as teleporting the atom, why can't we do the same for macroscopic objects?

 

[hammertime]

I don't use this distinction.
I just say that experiments are done regarding limited-subset-of-full-state, rather than full-state and it seems to be impossible to do any teleportation (or other) experiment operating on the full state.
Photons have well defined full-state: spin, momentum/position, that's all. For atoms that is not so easy.


Reference please!


But I must know what the Hilbert space describing this state is. And teleportation couples only subset of the full-state Hilbert space dimensions.

But it's still possible to teleport the full state - in other words, all the information that describes it - right? It's hard, sure, but doable.

 

[hammertime]

Hammertime, I guess for atoms and "macroscopic" objects like molecules yes, but for a big macroscopic object like a key we are very very far. It seems that for increasing complexity of the object the number of resources used scales exponentially. Even if there is a way, maybe it is too costly.

How do you know it scales exponentially. Can you show me the math?

 

[Drakkith]

Is there a difference between "teleporting" the state of an object and simply transmitting the information about the state of the object?

 

[Ryan_m_b]

Scanning? Teleportation? Nanobots? This is sort of going Star Trek here. Most of this makes little scientific sense. Can you bring it back to a specific question about something which is not born from fiction? Thanks.

I don't see what's so outlandish about this. Can you explain? I've made a few suggestions. Could you please tell me what's wrong with them?

Remember, things like the internet, space travel, and supersonic flight were once science fiction, too.

And alchemy was once considered a science. The fact that something we have no was not envisioned in the past has no bearing on whether or not things now will be envisioned in the future. DrChinese's point is that what you've said doesn't make sense in terms of science. What do you mean by scan (provide specific references from establishes science)? What do you mean by teleportation (provide specific references from establishes science)? What do you mean by nanobots (provide specific references from establishes science)?

On the latter I already responded to you that there was no reality in this. What you are doing here on this thread it seems is asking if your science fiction wish list could come true, ignoring lot's of legitimate opposition to it (like the definitions used for "teleport") and grasping that anything that seems like it supports your dream.

 

[hammertime]

And alchemy was once considered a science. The fact that something we have no was not envisioned in the past has no bearing on whether or not things now will be envisioned in the future. DrChinese's point is that what you've said doesn't make sense in terms of science. What do you mean by scan (provide specific references from establishes science)? What do you mean by teleportation (provide specific references from establishes science)? What do you mean by nanobots (provide specific references from establishes science)?

On the latter I already responded to you that there was no reality in this. What you are doing here on this thread it seems is asking if your science fiction wish list could come true, ignoring lot's of legitimate opposition to it (like the definitions used for "teleport") and grasping that anything that seems like it supports your dream.

What I mean by "scan" is "determine the position and type of each atom" so that we can build an entangled replica at the destination. I'm also wondering if we'll have to "scan" the object by determining the quantum state of each of its constituent atoms.

By "teleportation", I mean quantum teleportation, which has already been demonstrated on atoms and photons. I mean, if we can do it to a single atom, why not large numbers of them? It's just a matter of technical issues, right?

By "nanobots", I mean small, blood-cell-sized machines that traverse the object to scan from the inside, as opposed to having to scan from the outside, like with an ultra hi-res MRI machine.

And, with all due respect, people once said that flight, the internet, and space travel were a "dream". People once said laptops, cell phones, and cars were a "dream".

 

[Ryan_m_b]

What I mean by "scan" is "determine the position and type of each atom" so that we can build an entangled replica at the destination. I'm also wondering if we'll have to "scan" the object by determining the quantum state of each of its constituent atoms.

By "teleportation", I mean quantum teleportation, which has already been demonstrated on atoms and photons. I mean, if we can do it to a single atom, why not large numbers of them? It's just a matter of technical issues, right?

By "nanobots", I mean small, blood-cell-sized machines that traverse the object to scan from the inside, as opposed to having to scan from the outside, like with an ultra hi-res MRI machine.

And, with all due respect, people once said that flight, the internet, and space travel were a "dream". People once said laptops, cell phones, and cars were a "dream".

Ok now provide evidence that these things are possible and if they can be used in the manner you describe. I'm pretty sure that determining the position/momentum etc of all the atoms in a macroscale object whilst it is alive and moving is impossible.

I already addressed your last fallacy. The fact that in the past there were oppositions to ideas that came about has no bearing on whether or not there is a legitimate opposition to a current proposal.

 

[hammertime]

Ok now provide evidence that these things are possible and if they can be used in the manner you describe. I'm pretty sure that determining the position/momentum etc of all the atoms in a macroscale object whilst it is alive and moving is impossible.

You're right. Doing it while the object is alive is impossible. But there's nothing that makes cryogenically freezing the object impossible. Therefore, in principle, it's possible. So let's assume, for argument's sake, that the technical hurdles have been overcome and the object has been cryogenically frozen.

I already addressed your last fallacy. The fact that in the past there were oppositions to ideas that came about has no bearing on whether or not there is a legitimate opposition to a current proposal.

But it shows a trend.

 

[Ryan_m_b]

You're right. Doing it while the object is alive is impossible. But there's nothing that makes cryogenically freezing the object impossible. Therefore, in principle, it's possible. So let's assume, for argument's sake, that the technical hurdles have been overcome and the object has been cryogenically frozen.

This is not a proper way to address any topic. Many of the problems are unknown and addressing those hurdles will likely change the characteristics of the end product. I have already addressed your cryogenic statements https://www.physicsforums.com/showthread.php?t=519258". I must say it is frustrating to deal with your questions only to have you say "well forget about all that and let's just assume that none of those problems exist".

But it shows a trend.

I don't see what you aren't getting here. The fact that things have been discovered before is not indicative that things will be discovered in the future. You can't tack on the success of one field onto an unrelated field just because you want to, it's illogical and fallacious. Otherwise I could use that argument for anything, watch:

-Antimatter powered underwear that rocket jump you to work will be around in ten years
-After all none of that is technically impossible (it's not like FTL or anything)
-Anyone who says anything negative about the practicalities of it don't bother because I don't care, let's assume none of those impracticalities exist
-Anyone who objects still I would like to remind you that people once invented crossbows

 

[xts]

you teleport whichever state you want. You just need to be able to perform the right kind of measurement for teleportation.
Reference fo cont. variables telp.: http://arxiv.org/abs/0910.2713

Not quite as you say. This experiment utilizes Braunstein-Kimble protocol for teleporting continuous variables (S.L.Braunstein, H.J.Kimble, Teleportation of Continuous Quantum Variables, PRL, 26.Jan.1998, http://authors.library.caltech.edu/3827/1/BRAprl98.pdf)

The accuracy of the protocol is limited to measurement accuracy of position and momentum in teleportation scanner. Teleported state is not an exact copy of the original one (like it is in case of discrete variables) - it is just similar to it with accuracy equal to precision of classical measurement.

Even if we improve our precision, we never may reach "perfect" measurement of a continuous variable. Please note that the amount of classical information to be transmitted are outcomes of our measurements of position and momentum - as the accuracy increases, the amount of information increases accordingly. At the limit of "perfect" measurement reasulting with real number, infinite amount of information has to be transmitted.

 

[xts]

Is there a difference between "teleporting" the state of an object and simply transmitting the information about the state of the object?

For quantum objects you can't know the full information about the state, so it even makes little sense to think about complete information about state.

Quantum Teleportation allows you to restore original state of original object at the cost of destroying the original state, transmitting some "classical" information, and utilizing a pair of entangled particles.

 

[DrChinese]

What I mean by "scan" is "determine the position and type of each atom" so that we can build an entangled replica at the destination. I'm also wondering if we'll have to "scan" the object by determining the quantum state of each of its constituent atoms.

By "teleportation", I mean quantum teleportation, which has already been demonstrated on atoms and photons. I mean, if we can do it to a single atom, why not large numbers of them? It's just a matter of technical issues, right?

By "nanobots", I mean small, blood-cell-sized machines that traverse the object to scan from the inside, as opposed to having to scan from the outside, like with an ultra hi-res MRI machine.

And, with all due respect, people once said that flight, the internet, and space travel were a "dream". People once said laptops, cell phones, and cars were a "dream".

You cannot "scan" an atom to determine its properties. This has never been been done and in fact is impossible, I am sure you are aware of the Heisenberg Uncertainty Principle (HUP).

You can entangle 2 particles in such a way that the state of a third can sometimes be teleported (swapped). However, this has never been done on demand, it is simply something that occurs randomly in a subset of events. The remaining subset has nothing relevant changing and there is no way to tell the difference between the two.

You may know more about nanobot potential than I do, but that will not change either of my comments above.

Further, what you are imagining is that you are somehow building an exact replica of an object. That is not teleportation in my book, but regardless it is not feasible under any set of assumptions given that the HUP is accurate. My point is that what you call "difficult" is, for all intents, impossible.

Your analogy of a "dream" likewise makes no sense, as this implies anything is possible given a little time and technology. Good luck with that! Anyway, I don't recall any substantive articles to the effect that the internet, laptops or cell phones were impossible dreams. Early versions of these were around by 1984.

 

[hammertime]

You cannot "scan" an atom to determine its properties. This has never been been done and in fact is impossible, I am sure you are aware of the Heisenberg Uncertainty Principle (HUP).

You can entangle 2 particles in such a way that the state of a third can sometimes be teleported (swapped). However, this has never been done on demand, it is simply something that occurs randomly in a subset of events. The remaining subset has nothing relevant changing and there is no way to tell the difference between the two.

You may know more about nanobot potential than I do, but that will not change either of my comments above.

Further, what you are imagining is that you are somehow building an exact replica of an object. That is not teleportation in my book, but regardless it is not feasible under any set of assumptions given that the HUP is accurate. My point is that what you call "difficult" is, for all intents, impossible.

Your analogy of a "dream" likewise makes no sense, as this implies anything is possible given a little time and technology. Good luck with that! Anyway, I don't recall any substantive articles to the effect that the internet, laptops or cell phones were impossible dreams. Early versions of these were around by 1984.

Why would the HUP prevent building an exact replica of an object? It merely says that the more accurately we measure a particles position, the less accurately we can measure its momentum. But if we were to put an object at very low temperatures, each atoms momentum is negligible. They're essentially at rest. So what would stop us from determining the position of each atom?

Just think of it as a super hi-res MRI.

 

[Ryan_m_b]

You may know more about nanobot potential than I do, but that will not change either of my comments above.

"Nanobots" are one of those fields of science that have far more fictional publications than real. The idea behind it is the concept of building cell like machines but we're nowhere near even beginning to plan on how to design them. Some simple designs for things have been explored but they are akin to Leonardo da Vinvi's helicopters.

Why would the HUP prevent building an exact replica of an object? It merely says that the more accurately we measure a particles position, the less accurately we can measure its momentum. But if we were to put an object at very low temperatures, each atoms momentum is negligible. They're essentially at rest. So what would stop us from determining the position of each atom?

Just think of it as a super hi-res MRI.

You keep saying these things without offering any substance. Do you even understand what an MRI is? It would not help in these situations. Dr Chinese has accurately pointed out with you that there is no technology to completely map all the characteristics of an atom. Yes you can know the position of an atom but an atom is made of subatomic particles that are under the HUP.

And how do you imagine that an atomic "scan" of a bulk object could occur? I think it's time that you provided references for any proposals you have.

 

[DrChinese]

Why would the HUP prevent building an exact replica of an object? It merely says that the more accurately we measure a particles position, the less accurately we can measure its momentum. But if we were to put an object at very low temperatures, each atoms momentum is negligible. They're essentially at rest. So what would stop us from determining the position of each atom?

Then the HUP would be wrong, wouldn't it? So no, cooling an atom does not change that at all.

Of course, you could simply say that "getting close" when replicating an object is good enough. Who knows? But still, replicating an object atom by atom is not teleportation.

 

[hammertime]

Further, what you are imagining is that you are somehow building an exact replica of an object. That is not teleportation in my book, but regardless it is not feasible under any set of assumptions given that the HUP is accurate. My point is that what you call "difficult" is, for all intents, impossible.

Your analogy of a "dream" likewise makes no sense, as this implies anything is possible given a little time and technology. Good luck with that! Anyway, I don't recall any substantive articles to the effect that the internet, laptops or cell phones were impossible dreams. Early versions of these were around by 1984.

And an early version of macroscopic QT is around now. Right now, we can only teleport the state of one atom. Eventually, it'll be a small group (perhaps a few dozen), then a few hundred, etc.

Az Kurzweil puts it, technology grows exponentially. Even when a certain technology (like 2-dimensional transistor-based microprocessors) hits its physical limits, a new technology tends to take its place. So it stands to reason that we'll eventually be able to QT the state of a macroscopic object, thanks to advances in technology and scientific knowledge, right?

All it takes is one guy with a "Eureka!" moment.

 

[K^2]

Unfortunately, difficulty of teleportation of a system also grows exponentially, so the exponential growth of technology is not useful.

 

[Ryan_m_b]

Az Kurzweil puts it, technology grows exponentially. Even when a certain technology (like 2-dimensional transistor-based microprocessors) hits its physical limits, a new technology tends to take its place. So it stands to reason that we'll eventually be able to QT the state of a macroscopic object, thanks to advances in technology and scientific knowledge, right?

Kurzweil is a crackpot. He's taken Moore's law and applied it to everything with absolutely no evidence (his graphs are completely arbitrary with things like "writing" plotted alongside "agriculture" and "the internet" before being used to support his arguments). In other words he has done little more than http://xkcd.com/605/" . He also makes very weak arguments with little understanding of the real science. For example: he baselessly extrapolates Moore's law until there is a laptop that can match the human brain for power (and he made up that figure with some dodgy reasoning about the eye) and says "this is when AI and mind uploading will appear!". I can't remember who said it but one of his critics pointed out that Kurzweil has greatly confused knowledge growth with comprehension. Yes we have far better equipment and more knowledge but we have little more than a puddle of understanding in an ocean of data. Just look at the human genome project, yes we sequenced our entire genome but it's a decade on and we're still chipping away trying to figure out what it means (and we will be doing that for a very long time). A typical pre-2000 kurzweil statement on the subject would run along the lines of "once we've sequenced our genome we will be able to genetically engineer ourselves for immortality". Also please note that just because you can do more of something doesn't mean it will scale infinitely. Sure you can transfer all the properties of one atom to another but how are you going to do that with atoms burried behind others? And how are you going to have an exact stockpile of atoms at the other end in the exact same configurations?

I don't see why this thread has gone on for so long. If you had just read the first part of the wikipedia entry on the subject you will see that you have confused QT with Star Trek teleportation.

Quantum teleportation, or entanglement-assisted teleportation, is a process by which a qubit (the basic unit of quantum information) can be transmitted exactly (in principle) from one location to another, without the qubit being transmitted through the intervening space. It is useful for quantum information processing, however it does not immediately transmit classical information, and therefore cannot be used for communication at superluminal (faster than light) speed. Quantum teleportation is unrelated to the common term teleportation - it does not transport the system itself, and does not concern rearranging particles to copy the form of an object.

 

[hammertime]

What about non-quantum teleportation? What about the things that you see in Star Trek, where a body is converted to energy and then "beamed" to a destination. What challenges lie in the way of doing that?

 

[BruceW]

Quantum teleportation is fine for photons and atoms, since there are not many parameters needed to define the state.
But for a human there are an incredibly huge number of parameters. So to quantum teleport a human, you would have to couple an incredibly huge number of particle pairs.
Also, in quantum teleportation, the original human would be destroyed (since it is not possible to make an exact replica of a quantum state without affecting the original quantum state).
Also, since a classical communication of the outcome of a Bell state measurement must be done, the quantum teleportation can only be completed at the speed of light or less.

To answer "what if a body was converted to energy and beamed to a destination": Well, the only kind of teleportation that has been done is quantum teleportation. So if you were thinking of inventing non-quantum teleportation, you'd need to come up with some other method. (The only other way I can think of is via some kind of wormhole due to the laws of general relativity).

In any case, either of these methods for teleporting a human are way off in the future (if they are even possible at all).

 

[Ryan_m_b]

What about non-quantum teleportation? What about the things that you see in Star Trek, where a body is converted to energy and then "beamed" to a destination. What challenges lie in the way of doing that?

The challenge that there is no known mechanism by which this is possible. You might as well ask "what barriers exist to magic?" If you convert a human body to energy (and how you would achieve total mass-to-energy is a big question) you now just have a huge explosion to deal with. Put it this way, if I explode a nuclear bomb in one direction towards you, how exactly are you going to absorb the explosion and turn it back into a nuclear bomb?

It also violates some fairy fundamental physics, namely the fictional technology somehow maps (perfectly and without interfering) the properties of every particle of the object being transported. This obviously violates the HUP.