Talk:Quantum teleportation

WikiProject Physics (Rated C-class, High-importance)

Alternative name

"Thus, despite the provocative name, it is best thought of as a kind of communication, rather than a kind of transportation."

It's a pretty terrible name, then. Has anyone proposed or used an alternative name that better connotes communication? If so, please put it in the intro to the article in bold. — Preceding unsigned comment added by 71.167.62.7 (talk) 21:55, 15 August 2013 (UTC)

Teleportation is a kind-of transportation. Although one can think of it as a kind-of communication, it is also, defacto, a kind of transportation. The article, as written, may be placing the empahsis incorrectly. The name is appropriate. User:Linas (talk) 17:25, 20 November 2013 (UTC)
I agree with the OP. The term "quantum teleportation" should be deprecated in Wikipedia. Just arguing that it is 50% similar to the science-fiction notation of teleportation is not sufficient justification to use a term that is, at the same time, 50% misleading.
It should really be called "quantum communication" or something like that, to de-mystify it. Personally I like the moniker "quantum state transfer"; it has the necessary sobriety.
178.38.115.176 (talk) 15:24, 5 May 2015 (UTC)

I agree that the name 'quantum teleportation' is very confusing in etymology. A little better name is state teleportation, a true name should be called state transfer.

Recently, Wei proposes that a particle can teleport. This is called particle teleportation without questions. This makes quantum teleportation more meaningless. Temporarily Wei's paper on 'particle teleportation' is added as a exception. But the problem of misleading has not completely fixed yet. Davy2016 (talk) 16:51, 8 August 2016 (UTC)

Mistake

From what I see, the gate that has to be applied by the receiver in the case where both measurements are 1 is wrong. It should really be

0 1

-1 0

= Z*X, which is what the circuit diagram indicates: First quantum NOT (X), then phase shift (Z).

If you go back up, you will find that the state in the respective case is "wrong" - it has a global phase -1, and should really be

-\beta|0> + \alpha|1>

I have derived the equations myself and got this. 213.142.168.211 (talk) 15:02, 29 August 2013 (UTC)Daniel

I just checked the formulas in the article, and they appear correct to me; I don't see the mistake that you describe. User:Linas (talk) 18:51, 21 November 2013 (UTC)

There is no actual "Atom Teleportation"

The texts reads: "although single atoms have been teleported". That is plainly WRONG. If you read the papers used as reference and source, then it still is INFORMATION that is transported, not the actual atoms. Indeed it's not teleportation (of information) of atoms, but 'from atom to atom'. — Preceding unsigned comment added by 131.175.161.14 (talk) 09:58, 11 March 2014 (UTC)

I have corrected the error — Preceding unsigned comment added by 131.175.161.14 (talk) 10:03, 11 March 2014 (UTC)

I'm removing the frollowing text from the lead, because it is wrong, and is causing readers to miunderstand (see some of the comments and essays above).

Quantum teleportation is unrelated to the kind of teleportation commonly used in fiction, as it does not transport the system itself, does not function instantaneously, and does not concern rearranging particles to copy the form of an object. Thus, despite the provocative name, it is best thought of as a kind of communication, rather than a kind of transportation.

First of all, it is related, because it does transport the system itself! This follows from axiomatizations of QM, which basically state that the universe consists of bits and qubits; and there are two ways of moving a qubit: putting it on a horse and riding it somewhere, or quantum-teleporting it. Teleportation is a kind-of transport, this follows from the no-cloning/no-deleting theorems. True, it does not not function super-luminally (the no-communication theorem). It does concern re-arranging particles, although so far, we've only been able to re-arrange only two or three, and not even an entire atom, yet. Yes, it can be thought of as a kind-of communication, but it is also quite correct to think of it as a kind-of transportation. User:Linas (talk) 17:37, 20 November 2013 (UTC)

I also added a five-paragraph non-technical summary, which perhaps will help prevent mistakes like the above in the future. If there are other things that need to be explained in a non-technical way, give me a ping. User:Linas (talk) 20:15, 20 November 2013 (UTC)

It's not really correct to say that the universe is composed of bits and qubits. I understand the sentiment, but if you want to idealize the universe as a computer, then really the qubits are fundamental and bits are emergent, corresponding to qubits that are decohered. The reference to the no-communication theorem is also not quite right; qubits can carry information (in fact one bit per qubit) but the theorem refers instead to the impossibility of using entanglement for instantaneous communication. I'll do some rewriting of this soon, but am happy to discuss more here first if anyone wants. 24.61.8.127 (talk) 04:12, 14 December 2013 (UTC) (this last change I accidentally made w/o being signed in. Here is my real signature. Aram.harrow (talk) 04:14, 14 December 2013 (UTC))

The explanation is missing references and it sounds like original research, with too fancy expressions. Mstuomel (talk) 03:26, 30 January 2014 (UTC)
I have some concerns about it too, particularly the claim that qubits cannot encode bits (at all), which seems to contradict most reliable sources on quantum computing. I note that the editor who added the text (Linas) is/was blocked indefinitely, although on behavioral issues [1]. The text was added in violation of WP:BLOCKEVASION although that's the least of the concerns here. JMP EAX (talk) 06:58, 23 August 2014 (UTC)
If one wants to write something "non-technical" the bullet list from [2] appears a better source. JMP EAX (talk) 09:04, 23 August 2014 (UTC)
JMP EAX and Aram.harrow were correct in their concerns. The statements they refer to were wrong for precisely the reasons they say. Specifically, qubits are fundamental, not classical bits. It is incorrect that quantum bits cannot model classical bits. And the reference to the no-communication theorem seemed to misunderstand the content of that theorem. Presumably, with these problems solved, there should no longer be a conflict with another article so I will remove the banner now. Isocliff (talk) 14:30, 14 January 2015 (UTC)

What Happened to Ted?

So far, the article mentions three "people" who are hypothetically examining and "teleporting" quantum state information, "Alice," "Bob," and "Carol."

Those of us who were at least teenagers in 1969 remember Bob & Carol & Ted & Alice, which its wikipedia article describes as a "1969 comedy-drama film" about two married couples who almost have a foursome in bed.

Does the inclusion of "Carol" in the description reflect wider usage in the QM community (I've seen "Alice" and "Bob" used throughout papers on quantum teleportation to identify hypothetical observers of quantum states in discussions of quantum teleportation, and the authors of the June 3 TU Delft paper on "unconditional quantum teleportation" actually name their quantum teleportation devices "Alice" and "Bob" [1]), or was it just a bit of humor on the original editor's part, alluding to the film I described? loupgarous (talk) 02:15, 10 June 2014 (UTC)

They are common names used in cryptography and physics. Carol is the classic third participant. Eve is commonly the eavesdropper. See Alice_and_Bob. 134.134.137.73 (talk) 21:35, 11 June 2014 (UTC)

Individual states?

A general question about the experiments that verify EPR, quantum teleportation, entanglement, non-locality etc.

When the experiment is done, is just one system and outcome at a time being observed, in an individualized fashion, with pauses between?

Or are the systems being produced in a rapid-fire way, one after another, and only final intensities (or perhaps statistics) being measured?

In other words I'd like a clearer picture of the individualization of the systems in the experiment. I've not seen this treated, so far, in the Wikipedia articles I've read on the subject. If it is already appears somewhere in Wikipedia, I'd be interested in knowing where. 178.38.115.176 (talk) 07:52, 5 May 2015 (UTC)

How is it implemented physically?

These question pertain to the real-world particles that might occur in the section called "Formal presentation".

(1) In a real experiment corresponding to this mathematical setup, what kinds of particles are A,B,C? Electrons? Photons?

(2) I noticed that the joint AB state is symmetric under exchange of the two particles. Does that mean A, B are identical and are bosons?

(3) On the other hand, the AC states are neither symmetric nor antisymmetric under exchange. Does that mean A and C are necessarily not the same kind of particle?

(4) Bob would send his qubit through the unitary quantum gate given by the Pauli matrix ${\displaystyle \sigma _{3}}$. How does he execute this unitary operation with, say, photons or electrons in a real experiment?

178.38.90.0 (talk) 18:49, 5 May 2015 (UTC)

Which rotations?

The above-mentioned three gates correspond to rotations of π radians (180°) about appropriate axes (X, Y and Z).

Rotations of what? Is the spin representation of SU(2) being used? The named rotations all have order two and general an abelian group G of order 8 in SO(3). But the listed gates have orders 2, 2, and 4 and generate a nonabelian group of order 8 in O(2), namely the symmetries of the square. They lie in U(2) ∩ GL(2,R), but not in SU(2) which projects to SO(3). What is the relationship to X, Y, Z?

Something is wrong here?

178.38.90.0 (talk) 18:49, 5 May 2015 (UTC)

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Off-topic/uninformative paragraph

Hello Jim1138:

As it is, the following paragraph appears to me off-topic:

"In October 2015, scientists from the Kavli Institute of Nanoscience of the Delft University of Technology reported that the quantum nonlocality phenomenon is supported at the 96% confidence level based on a "loophole-free Bell test" study.[10][11] These results were confirmed by two studies with statistical significance over 5 standard deviations which were published in December 2015.[12][13] "

1. First of all, these are not the first works supporting the existence of non-locality. Early experiments where conducted by John Clauser and Stuart Freedman in 1972, and later by Alain Aspect in 1982.
2. Second, should we cite these experiments without explaining what they are, or at least what they show? I mean here the above-mentioned paragraph talks about non locality but does not relate it with teleportation. The only relation somehow is that we need entanglement to perform teleportation, but there is already a pointer to the Wikipedia page to "quantum entanglement" in the first sentence. There the reader will find all the information about entanglement and about how to test for entanglement.
3. Thirdly, even though Bell experiment are somehow related to entanglement, the goal of these experiments has nothing to do with teleportation. For example, Bell's inequalities are known from the 60's while the teleportation has devised only from the 90's. In fact the relation between these two things is highly non-trivial.

For these reasons I think that, as it is, the above paragraph is uninformative and appears to be off-topic, therefore it should be removed. BooBoo314159 (talk) 11:32, 10 October 2017 (UTC) ; edited 09:28, 11 October 2017 (UTC)

Removal of footnote template?

It's about 5 years old and many new sources have been added since then. (The "arxiv.org" link below wasn't added by me, it's just listed here for some reason.) Mr. Dodo'sss (talk) 12:42, 12 November 2017 (UTC)

Faster than light "not currently" feasible

Since quantum teleportation depends on classical communication as one of its components, and that can proceed no faster than the speed of light, there's no way quantum teleportation can communicate faster than light unless there's already a classical way of doing so, e.g. involving exotic distortions of spacetime like wormholes. Even so, it would be the special spacetime topology responsible for the FTL communication, not the teleportation protocol itself. Therefore I think we should not suggest, as the previous wording "cannot currently be used" did, that quantum teleportation might some day might enable FTL communication.CharlesHBennett (talk) 21:53, 18 January 2018 (UTC)

dubious new section: Three particle entangled teleportation system

recently different IPs have repeatedly added a dubious section on a paper about "3-particle teleportation". The section is written to promote the author of that paper and his institution. Moreover, what is discussed in that paper (among rather weird mentions of Planck length, topology, a "Physical System Theory Model and its counterpart as consciousness system model" that seem to have no bearing on the actual protocol) is the old idea that a multi-partite entangled state can be used to teleport from A to B with the assistance of the remaining parties, that was first published in more general form in W. Dür & J. I. Cirac (2000). "Multiparty teleportation". J. Mod. Opt. 47 (2–3): 247–255. doi:10.1080/09500340008244039.. The paper linked to in this section also discusses a generalization of teleportation to d-level systems, that was in general discussed by Werner in 2001 (Werner, Reinhard F. (2001). "All teleportation and dense coding schemes". J. Phys. A: Math. and Gen. 34 (35): 7081. arXiv:quant-ph/0003070. doi:10.1088/0305-4470/34/35/332.). I support @Dmr2:, who removed the section as "questionable"; if one wants to write a section on multiparty teleportation, it should cite the original sources (and be written in a neutral way). In order not to stat an edit war by simply removing it again i'd like to discuss the issue here. --Qcomp (talk) 17:27, 6 October 2018 (UTC)

having had another look at the literature, I propose to merge the two sections on teleportation using multipartite states and teleportation using higher dimensional systems into one section called "Generalizations of the Teleportation Protocol". The rational is that both are, in my view, rather technical and do not add conceptionally new aspects. Especially in the multipartite case there are quite number of different directions to generalize: (i) controlled teleportation (where C can control whether A can teleport to B) (ii) "shared teleportation" (where B and C receive the state jointly and only can access it in a cooperative fashion), (iii) genuine multi-receiver teleportation (where A wants to send a state to a group of receivers) (iv) imperfect versions (where the available states do not allow single-copy ideal teleportation, but still provide a finite quantum capacity). I propose the following replacement:
Generalizations of the Teleportation Protocol
The basic teleportation protocol for a qubit described above has been generalized in several directions, in particular regarding the dimension of the system teleported and the number of parties involved (either as sender, controller, or receiver). A generalization to ${\displaystyle d}$-level systems (so-called qudits) is straight forward and was already discussed in the original paper by Bennett et al. [REF]: the maximally entangled state of two qubits has to be replaced by a maximally entangled state of two qudits and the Bell measurement by a measurement defined by a maximally entangled orthonormal basis. All possible such generalizations were discussed by Werner in 2001 [Werner, Reinhard F. (2001). "All teleportation and dense coding schemes". J. Phys. A: Math. and Gen. 34 (35): 7081. arXiv:quant-ph/0003070. doi:10.1088/0305-4470/34/35/332.]. The generalization to infinite-dimensional so-called continuous-variable systems was proposed in [Braunstein, S. L.; Kimble, H. J. (1998). "Teleportation of Continuous Quantum Variables". Phys. Rev. Lett. 80: 869. doi:10.1103/PhysRevLett.80.869.] and lead to the first deterministic teleportation experiment. [Furusawa, A.; Sørensen, J. L.; Braunstein, S. L.; Fuchs, C. A.; Kimble, H. J.; Polzik, E. S. (1998). "Unconditional Quantum Teleportation". Science. 282: 706. doi:10.1126/science.282.5389.706.]
The use of multipartite entangled states instead of a bipartite maximally entangled state allows for several new features: either the sender can teleport information to several receivers either sending the same state to all of them (which allows to reduce the amount of entanglement needed for the process) [W. Dür and J. I. Cirac (2000). "Multiparty teleportation". J. Mod. Opt. 47 (2–3): 247–255. doi:10.1080/09500340008244039.] or teleporting multipartite states [Yeo, Ye; Chua, Wee Kang (2006). "Teleportation and Dense Coding with Genuine Multipartite Entanglement". Phys. Rev. Lett. 96: 060502. doi:10.1103/PhysRevLett.96.060502.] or sending a single state in such a way that the receiving parties need to cooperate to extract the information [Karlsson, Anders; Bourennane, Mohamed (1998). "Quantum teleportation using three-particle entanglement". Phys. Rev. A. 58: 4394. doi:10.1103/PhysRevA.58.4394.]. A different way of viewing the latter setting is that some of the parties can control whether the others can teleport.

Did you know nomination

The following is an archived discussion of the DYK nomination of the article below. Please do not modify this page. Subsequent comments should be made on the appropriate discussion page (such as this nomination's talk page, the article's talk page or Wikipedia talk:Did you know), unless there is consensus to re-open the discussion at this page. No further edits should be made to this page.

The result was: rejected by Mandarax (talk) 19:36, 30 November 2020 (UTC)
Thank you for your work on the article, but, unfortunately, it's not eligible for DYK.

5x expanded by Bml6789 (talk) and Krisch53 (talk). Nominated by Bml6789 (talk) at 20:44, 25 November 2020 (UTC).

• Regrettably, this nomination does not qualify for DYK. The expansion is just short of 2x (21452 to 41499 prose characters), far from the 5x required, which is not feasible for an article that was so long to begin with. Should the article eventually become a Good Article, it could be eligible if nominated within seven days of passage. BlueMoonset (talk) 22:25, 27 November 2020 (UTC)

References

1. ^ http://arxiv.org/abs/1404.4369
2. ^ Llewellyn, Daniel; Ding, Yunhong; Faruque, Imad I.; et al. (December 23, 2019). "Chip-to-chip quantum teleportation and multi-photon entanglement in silicon". Nature Physics. 16: 148–153. doi:10.1038/s41567-019-0727-x. Retrieved 25 November 2020.