# Talk:Quantum teleportation

WikiProject Physics (Rated C-class, High-importance)
This article is within the scope of WikiProject Physics, a collaborative effort to improve the coverage of Physics on Wikipedia. If you would like to participate, please visit the project page, where you can join the discussion and see a list of open tasks.
C  This article has been rated as C-Class on the project's quality scale.
High  This article has been rated as High-importance on the project's importance scale.

## 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)

## 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)

When you have finished reviewing my changes, please set the checked parameter below to true or failed to let others know (documentation at {{Sourcecheck}}).