Talk:Quantum teleportation

message: 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)
replies: text: 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)
thread_title:  Mistake 

message: 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)
thread_title: There is no actual "Atom Teleportation"

message: 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)
replies: text: 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)

text: The explanation is missing references and it sounds like original research, with too fancy expressions. Mstuomel (talk) 03:26, 30 January 2014 (UTC)
replies: text:  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 . 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)

text:  If one wants to write something "non-technical" the bullet list from  appears a better source. JMP EAX (talk) 09:04, 23 August 2014 (UTC)
replies: text:  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)

text:  As for interpretations this article is rather one-sided. For more see  JMP EAX (talk) 09:42, 23 August 2014 (UTC)
thread_title:  removed text from lead 

message: 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" http://arxiv.org/abs/1404.4369), 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)
thread_title:  What Happened to Ted? 

message: 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)
thread_title: Individual states?

message: 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 \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)
thread_title:  How is it implemented physically? 

message: 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)
thread_title:  Which rotations? 

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thread_title:  External links modified 

message: 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] "
# 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.
# 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.
# 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)
thread_title:  Off-topic/uninformative paragraph 

message: 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)
thread_title:  Removal of footnote template?  

message: 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)
thread_title:  Faster than light "not currently" feasible 

message: In the end, it said (quote): Challenges faced in quantum teleportation include the no-cloning theorem which sets the limitation that creating an exact copy of a quantum state is impossible, the no-deleting theorem that states that quantum information cannot be destroyed, the size of the information teleported, the amount of quantum information the sender or receiver has before teleportation, and noise that the teleportation system has within its circuitry. Quantum teleportation, like any other sort of communication, cannot transfer information faster-than-light (no-communication theorem). 
1. The protocol here in this text is for sending any quantum state, even ones that are unknown to the sender, and it does this by sending - not copying - the state. So it is meaningless to talk about the no-cloning theorem? It even says in the first reference cited, in the introduction, that it is possible to teleport an unknown state. (Also if the state is known to be orthogonal to some known basis then its possible to "side-step" the no-cloning theorem. For example it is possible to copy a known boolean value with CNOT since we know all boolean states are orthogonal to the {0,1}^n basis/comutational basis)
2. "the no-deleting theorem that states that quantum information cannot be destroyed, the size of the information teleported, the amount of quantum information the sender or receiver has before teleportation" ← this sounds weird to me. The size of the information sent is "one qubit" for the basic protocol, and it is known, and the qubit can be in any state (see above).
I ended up removing the paragraph.  · · · Omnissiahs hierophant (talk) 16:43, 8 November 2021 (UTC)
replies: text: I think you are right. The no-cloning theorem is not a challenge for quantum teleportation. It is rater one reason why quantum teleportation is necessary for certain tasks, and cannot be replaced by classical communication. Similar for the no-deletion theorem. Also, the sentence about faster-than-light communication should be preserved in the introduction (as you did), because it is a very common misunderstanding that quantum teleportation would achieve such a thing. --Geek3 (talk) 17:26, 8 November 2021 (UTC)
thread_title:  About the introduction text 

message: If we have an article on this, I can't find it. This is the (fairly) old idea of extracting energy from the vacuum, and there's an interesting  new article on this here: https://www.quantamagazine.org/physicists-use-quantum-mechanics-to-pull-energy-out-of-nothing-20230222/
Excerpt:
"... 15 years ago, Masahiro Hotta, a theoretical physicist at Tohoku University in Japan, proposed that perhaps the vacuum could, in fact, be coaxed into giving something up ...
The first skeptic of quantum energy teleportation was Hotta himself. ...
Hotta found, to his surprise, that a simple sequence of events could, in fact, induce the quantum vacuum to go negative — giving up energy it didn’t appear to have. “First I thought I was wrong,” he said, “so I calculated again, and I checked my logic. But I could not find any flaw.”
The trouble arises from the bizarre nature of the quantum vacuum, which is a peculiar type of nothing that comes dangerously close to resembling a something. ..."
Anyway, interesting  stuff. Hotta himself has no Wikibio, and perhaps merits one. --Pete Tillman (talk) 20:06, 27 February 2023 (UTC)
thread_title:  Quantum energy teleportation