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".