# Quantum energy teleportation

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One of the most unpleasant thing about quantum entanglement is that it can't be used for information or energy transfer. No-communication theorem - Wikipedia

Some scientists, however, are trying to overcome this problem: Squeeze light to teleport quantum energy | New Scientist

However this method doesn't seem to be practical for any significant amounts of energy, if at all.

Do you think there could be some quantum effects which may allow us to transfer significant amounts of energy for a large distances with high efficiency? Possibly something on the verge of classical and quantum physics?

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The nature of so-called "quantum teleportation" is very widely, very deeply misunderstood. Nothing is travelling "instantly", so nothing is teleported. Energy, of course, cannot be teleported either.

What these experiments do is build highly correlated pairs of particles, and keep quantum coherence for incredibly long distances. They can then "switch off" coherence, so to speak, and can select sub-states completely correlated to each other. That's very impressive in and of itself, but no teleportation AFAIK.

I wouldn't call this "teleportation", and I don't know who introduced that term, but it's a misnomer and it causes confusion to no end. I for one would prefer that scientists used a more understated vocabulary. But it seems to be the case that the more sci-fi it sounds the more hype it's going to stir. I think that's unfortunate.

No, Star Trek is not around the corner. I wish it would.

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An article that describes entanglement as “a change to one particle always affects its partner in a particular way” is not to be trusted to get anything right.

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There are claims that quantum entanglement is behind photosynthesis. Untangling the quantum entanglement behind photosynthesis (phys.org)

Is it potentially useful for a long distance energy transfer?

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1 hour ago, Bond777 said:

There are claims that quantum entanglement is behind photosynthesis. Untangling the quantum entanglement behind photosynthesis (phys.org)

Is it potentially useful for a long distance energy transfer?

Long-distance energy transfer is possible. It's called radiation. It's constrained to transfer speeds equal to the speed of light in vacuum, at most. I don't see how entanglement could achieve anything better than c-propagation for energy.

As to claims that quantum entanglements play a part in photosynthesis, I wouldn't be terribly surprised if that happened. There have been claims that quantum entanglement participates in birds finding their bearings in long migrations. There are many claims of that sort. I would tend to be cautions about those claims, but it's possible.

My sceptic half says that entanglement, in the usual meaning, is normally associated with cold, non thermal, conditions. But here's what I've found:

I would think that there must be a conceptual bridge between claims of entanglement playing a part in biological systems and study of entanglement in strongly interacting systems. But I would have to read this material more carefully. In the meantime, I'd be very interested in what other users have to say.

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5 hours ago, joigus said:

Long-distance energy transfer is possible. It's called radiation.

Unfortunately, radiation is either harmful and/or requires precise direction. Strongly absorbed by the environment. Therefore it may never be helpful to get rid of the power lines. I thought it is quite obvious.

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57 minutes ago, Bond777 said:

Unfortunately, radiation is either harmful [...]

Not all radiation is harmful. Long wavelengths are much less harmful than short ones.

1 hour ago, Bond777 said:

[...] and/or requires precise direction.

Yes, that's true. But that's why we have antennas. They exploit interference.

57 minutes ago, Bond777 said:

Strongly absorbed by the environment.

No. Not all matter is a good absorber of radiation. Some matter reflects radiation, other matter diffracts it or transmits it. Most interstellar space is quite transparent to radiation. Air scatters radiation, rather than absorb it, for the most part.

The point is quantum teleportation has particular features that are in no way like "sending something from A to B instantly".

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1 hour ago, Bond777 said:

Unfortunately, radiation is either harmful and/or requires precise direction.

Some radiation is good for you, EM radiation in the ultraviolet wavelength helps your body produce vitamin D.

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51 minutes ago, joigus said:

Not all radiation is harmful. Long wavelengths are much less harmful than short ones.

Long wavelength require huge antennas regularly. Though there are experiments with electrically short antennas. It cannot be precisely directed and therefore long distance transmission is extremely inefficient. Another thing if there would be some intimate connection between two antennas, which resemble quantum entanglement. Maybe something similar, but not exactly classical entanglement.

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34 minutes ago, Bond777 said:

Long wavelength require huge antennas regularly.

Long in this context is anything bigger than ~1 micron, i.e. non-ionizing.

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1 hour ago, Bond777 said:

not exactly classical entanglement. [...]

There is no such a thing. I had a series of conversations with a friend who was refereeing for PRL on submitted papers that were using such a misnomer. It was decided that it had nothing to do with entanglement, and all the effects could be understood with the superposition principle. Classical field theory doesn't deal with photons (as particles), so there can be no entanglement from the point of view of classical fields. It doesn't even start to make sense.

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Posted (edited)
10 hours ago, joigus said:

It was decided that it had nothing to do with entanglement, and all the effects could be understood with the superposition principle.

Could you give more details on it? Which effects exactly?

Edited by Bond777
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3 hours ago, Bond777 said:

Could you give more details on it? Which effects exactly?

Very subtle, and I'm not sure to what extent consequential. See, e.g., https://physics.stackexchange.com/questions/334478/mathematical-definition-of-classical-entanglement

Quote

This difference not withstanding, several practical implementations have to date been made to demonstrate that if the requirement for entanglement in certain quantum protocols does not include a requirement for it to be nonlocal, such quantum protocols can be implemented with the aid of classical non-separability. Examples include quantum walk (1), the Deutsch–Jozsa algorithm (2) and characterization of quantum channels (3). These are nontrivial examples, implying that classical non-separability does seem to share some essential feature with quantum entanglement.

(My emphasis.)

This, of course, can only mean that in those cases classical fields can be used as a workable approximation. Classical field theory cannot give you any phenomenology that's not already contained in quantum field theory, as QFT is the fundamental theory as we know it.

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There are attempts to use some quantum effects in WPT:

Quote

Another recent findings show that it is possible to exploit a parity-time-symmetric circuit, incorporating a nonlinear gain saturation element, to induce robust wireless power transfer between the coils45. In a yet another method, a third coil is utilised to mediate efficient wireless power transfer between the coils46. Hence, we anticipate that the proposed TQD based scheme could be implemented practically.

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Entanglement is a quantum effect, but not all quantum effects are entanglement

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23 hours ago, swansont said:

Entanglement is a quantum effect, but not all quantum effects are entanglement

Obviously. I didn't insist it has to be entanglement only.

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• 2 weeks later...

Could we imagine the way in which two remote antennas (transmitter and receiver) could be classically entangled? Could someone shed more light on the classical entanglement? For example, one related to electromagnetic circuits?

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As joigus has already said, there is no such thing as classical entanglement. It is an inherently quantum effect.

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Quote

Classical systems can be entangled. Entanglement is defined by coincidence correlations.

It is the purpose of this paper is to discuss lossy classical systems and show that such systems can mimic quantum correlations.

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6 minutes ago, Bond777 said:

Correlations at a distance is not synonymous with "entanglement". We experience correlations at a distance every day. In quantum entanglement it is essential that there is an observable "number of particles" so that you can tag particle 1 and particle 2. The quantum state is an arrangement of 2-particle states that cannot be factored:

$\left|12\right\rangle -\left|21\right\rangle$

You cannot do that with classical fields. Also, certain polarisation choices allow you to contradict classical logic. If A, B, and C are certain statements "the car is red", or "the pencil is upwards", or anything you can conceive classically, you always have:

$P\left(A,\neg B\right)+P\left(B,\neg C\right)\geq P\left(A,\neg C\right)$

Read: Probability of statement A and not B plus probability of statement B and not C is greater or equal to probability of statement A and not C.

This is just as long as you can write properties A, B, and C as having a certain unknown value at the same time. Something like this:

Quantum mechanics contradicts this. There are certain observables that you can pick for which QM predicts:

$P\left(A,\neg B\right)+P\left(B,\neg C\right)< P\left(A,\neg C\right)$

I know of no example of mechanical rods or any other classical system that can reproduce that. I also think the complex-number character of quantum amplitudes has a lot to do with this.

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4 hours ago, joigus said:

Correlations at a distance is not synonymous with "entanglement". We experience correlations at a distance every day.

What correlations at distance could exist between transmitter and receiver?

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I was referring to the usual, i.e., speaking over the phone. Correlations at a distance are not magical, or anything new. But these correlations have to travel from Alice to Bob.

Quantum correlations in entangled states are of a different nature. First of all, and most important, the word that Alice sets in her system is random. It's not like she can decide to send the word "ALERT" to Bob. That would be a code in binary 0100101101... etc. that she chooses. But she can't do that. All she can do is pick a spin projection --that much she can choose-- and see what word her system produces, which sometimes will be 0101001101..., other times 1101001000..., etc. Then she knows that, provided Bob has his magnets oriented in the same direction, he will measure 1010110010..., 0010110111..., etc. (the "complementary" words). She gains knowledge about Bob's state automatically. But the salient state is random. And were Bob to measure a different projection of spin, their respective states would be as uncorrelated as if they had never been in contact.

This is a bit like a system that scrambles random words, so that the other user has the key to unscramble the message --the key being the particular projection they're going to measure--, but the words being completely random sequences --non-messages. What the uses of this technology would be, I don't know. But it's not completely obvious to me how they would take advantage of this technology.

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10 hours ago, joigus said:

I was referring to the usual, i.e., speaking over the phone. Correlations at a distance are not magical, or anything new. But these correlations have to travel from Alice to Bob.

Theoretically, EM waves could travel from transmitter to receiver by means of quantum tunneling, avoiding any attenuation in the environment. We need to have some long distance correlation between the both. Another possibility is to use magnetic induction or resonance between the two circuits. But again in order to make it work it efficiently over long distances we need to have magnetic field lines closed between the two over long distances. This effect suppose to resemble self-focusing magnetic lens.

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Posted (edited)
2 hours ago, Bond777 said:

Theoretically, EM waves could travel from transmitter to receiver by means of quantum tunneling, avoiding any attenuation in the environment.

Quantum tunneling is not free from attenuation. Look at this Wikipedia animation, for example:

Also, quantum tunneling happens just next to the barrier, not far away. It's a completely different effect.

Edited by joigus
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12 hours ago, joigus said:

Also, quantum tunneling happens just next to the barrier, not far away. It's a completely different effect.

It depends on De Broglie wavelength, which could be quite large in radio waves.

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