Talk:Quantum teleportation/Archive 2

Diagram

Rugburner (talk) 01:00, 24 March 2010 (UTC) This article is so bad I've registered just to edit it and add a diagram. Which having spent half an hour doing in paint, I now discover I can't do. I'm too shiny new.. Regardless the point has been made several times that this is an encyclopedia not a text book or professorial manual and should begin with a simple understanding of wtf it is. The math can stay lower down, but it must make simple sense. As someone with a phd chemistry and more than a passing understanding of quantum mechanics I should know what this is on about by now but I don't. I'm now going to make a series of minor edits to get up to 10 and enable my drawing to upload. as for this: "and use the two bits to select one of four ways of recovering c. The upshot of this protocol is to permute the original arrangement ((a,b),c) to ((b′,c′),a), that is, a moves to where c was and the previously separated qubits of the Bell pair turn into a new Bell pair (b′,c′) at the origin." That is as clear as mud. what 4 ways? permute does not compute.. and particularly this seemed to be the first reference to bell pair and was not hyperlinked. This lacks any experimental section or references to atoms and entangled photons as examples. I realise you're paralized by fear someone may think the matter or even photons are being teleported. But it can be clearly stated the bell pair are seperated and transmitted classically, and represent the teleportation equipment. As a side note this confusion wouldn't result if physicists would resist making highly overstated wildly exaggerated claims Rugburner (talk) 01:00, 24 March 2010 (UTC)

Rugburner (talk) 01:15, 24 March 2010 (UTC) I've uploaded the diagram to wiki commons file name "quantum teleportation scheme.jpg" http://commons.wikimedia.org/wiki/File:Quantum_teleportation_scheme.jpg if someone else can stick it in.. It is certainly not perfect but it's my experience that once something is done in life others will edit and correct, which they're more than welcome to do. afterall thats how this place is supposed to work I believe. Seems to have worked on me. Rugburner (talk) 01:15, 24 March 2010 (UTC)

Rugburner (talk) 02:00, 24 March 2010 (UTC) Have added an experiment section, I don't doubt it's a bit iffy as I came to this page to understand it better in the first place. I would ask that people not completely delete it as something of the kind needs to be there. Suspect that example doesnt resolve down from 4 bell states?? I don't know if this works for other properties than spin and energy??? What is tested about photons? wavelength? At least take away the need for examples.Rugburner (talk) 02:00, 24 March 2010 (UTC)

What it that advantage of using quantum teleportation?

If you have to send 2 bits by classical means just to get 2 bits from a transmitted quantum state, then what's the purpose? It has been said that it could be used for secure transmission since only the owner of 1/2 of the entangled pair could use the classically transmitted bits to read the information. Is this exciting for reasons other than cryptographics? Billk28 (talk) 03:53, 24 May 2010 (UTC)

Its exciting because it allows you to transmit quantum information, i.e. qubits. From axiomatic formulations of qunatum mechanics, we know that the entire universe consists of two things: bits and qubits. We've long known how to move bits on a wire, but moving qubits required saddling up a horse and riding it somewhere. Teleportation allows the qubits to be moved, without actually having to move the actual atoms (by horse, airplane or freight express). User:Linas (talk) 17:18, 20 November 2013 (UTC)

How does this theory actually happen??

Please can somebody seek out a real world example of the physical apparatus which allows this sort of thing to happen. It is done with what objects and how? (lasers mirrors, smoke,.. whatever)The theory is fine but could it be made clearer if the physical functioning of the way in which to do it is explained. Otherwise it might be seen to be mysterious, when it shouldnt. —Preceding unsigned comment added by 220.253.12.24 (talk) 08:42, 3 October 2010 (UTC)

Of course, the "Phds" appears to be unable to explain something without bizarre maths formulas. Roughly speaking, imagine the quantum teleportation as two glass cubes "A" and "B". If you point a laser at the cube "A", the light will exit on the cube "B" while the laser does not physically move from one cube to another (the space between the cubes remains empty), the light is "teleported" between the two cubes. And even if you put a wall between the two cubes the laser will continue into the cube "A" and leaving on the cube "B". The cubes in my example are the atoms (or photons) used for the EPR effect, and the laser would be the information. 200.189.118.162 (talk)

Just want to point out that there is a lot more to teleporting than what meets the eye :) If you can 'inject' energy through it, you definitely are sending 'information' even if in a unprocessed state. Recent experiments seems to say that plant can do it? We might have to redefine what information is in 'useful' and 'not useful'? If that is correct??

Just a thought. 178.30.9.75 (talk) 18:25, 21 January 2011 (UTC)

How we can describe the experiment justifiably

Currently the article says this, which I think is an overstatement: "In April of 2011 a means to teleport information without data loss was discovered." I didn't find the phrase "data loss" in the cited article; and in the original article in Science where the results are reported, their graph of "output" is quite a bit fuzzier than their graph of "input". Besides, even if the cited article said this, I don't think that's sufficient: maybe they're science journalists who could misunderstand something or exaggerate, and it's an extraordinary claim which would require extraordinary evidence. I suggest basing the statement about this experiment on a summary of the following sentence from near the end of the Science article: "We have demonstrated an experimental quantum teleporter able to teleport full wave packets of light up to a bandwidth of 10 MHz while at the same time preserving the quantum characteristic of strongly nonclassical superposition states, manifested in the negativity of the Wigner function." Lee, Noriyuki (2011). "Teleportation of Nonclassical Wave Packets of Light". Science. 332 (6027): 330–333. doi:10.1126/science.1201034. Retrieved 20110426. {{cite journal}}: Check date values in: |accessdate= (help); Unknown parameter |coauthors= ignored (|author= suggested) (help); Unknown parameter |month= ignored (help) I suggest summarizing this as "Lee et al. state that they have demonstrated teleportation of wave packets of light up to a bandwidth of 10 MHz while preserving strongly nonclassical superposition states." My understanding is that they preserved (some) nonclassical superposition, not that they preserved perfectly all of the nonclassical superposition of an individual wave packet. ☺Coppertwig (talk) 21:45, 30 April 2011 (UTC)

I was the original poster of the content and will admit that due to an oversight the language used is not presented within the actual article. The original references were: http://www.bit-tech.net/news/hardware/2011/04/18/light-wave-teleported-without-losing-data/1 and http://www.escapistmagazine.com/news/view/109318-Researchers-Succeed-at-Quantum-Teleportation-Breakthrough. Both use the language mentioned earlier. One of the articles sites the base article listed, the other does not. Since by technicality it is exorbitantly unlikely to find a "perfect" data transfer in any system I acknowledge and support your conclusion.

Travza (talk) 08:46, 2 May 2011 (UTC)

This article is a insult to real science

I carefully read the article ... And I saw on the same 10% relevant content (although deeply buried beneath meaningless mathematical formulas for the overwhelming majority of humanity) against 90% "Is impossible to teleport information, do not think that, if you insist you are a heretic and will burn!!" This text was written by a scientist or a religious solely concerned with protecting their precious religious dogmas? And Why "insult to real science"? Because real science do not turn theorems and hypotheses on religious dogma. 200.189.118.162 (talk) —Preceding undated comment added 17:44, 23 September 2011 (UTC).

quantum teleportation using nuclear magnetic resonance

• Complete quantum teleportation using nuclear magnetic resonance by M. A. Nielsen , E. Knill , R. Laflamme

Thom5738 (talk) 05:18, 26 February 2012 (UTC)

This is horribly written.

I've just spent 30 minutes or so trying to get my head around whats actually going on.

The qubits that get "entangled and teleported" actually send a message that can be reduced to a set of commonly understood analogue or Boolean values. To keep it simple, and applied for a laser, for example, 0 = not horizontally polarized, 1 = horizontally polarized, obviously by some consistent measurement (the actual polarisation angle being a possible analogue option). These 0s and 1s would be randomly generated, some physical noise property probably being sufficient to do this.

A laser (most sensibly local to the transmitter), would be used to generate a random qubit stream (photons). A small proportion of these photons would then be measured locally to determine if they are 0 or 1. The transmitter would then take these values to control, in some fashion, a more traditional transmission, possibly by changing an encryption protocol. The reciever would make the same measurement of the random qubit stream (photons) to determine if they are 0 or 1. This informs the reciever as to how to decrypt the traditional message.

This, potentially, makes the traditional message as hard to decrypt as a OTP encryption with a length greater than the message itself, without also requiring a copy of the OTP encryption to be held at both the transmit and recieve ends.

Yeatesi (talk) 16:09, 13 May 2012 (UTC)

I agree it is poorly written, I've been trying to address that issue. I will again have a bit of an edit to see if I can emphasise the differences between a qubit and a classic bit.

The process you have come away with seems to be more of a random noise generator creating a key for a standard transmission system. The qubits can't be measured or observed prior to reaching their destination, or they are indeed no more than a source of noise. Penyulap ☏ 17:33, 13 May 2012 (UTC)

A quantum bit cannot hold more than one bit of classical information, so analogue information is out. Using this method to send boolean values is pointless, you need to send two bits anyway so use one of those channels to transmit a pure boolean bit. There is no random number generation required and this scheme has no thing to do with cryptography. Skippydo (talk) 21:42, 13 May 2012 (UTC)

It is true that the qubit holds one bit of classic information, and you need to send two qubits for one bit of classic. It's not possible to use channels according to the references given or the method used, as both bits in the pair are required as there is a sender and a receiver, and they both destroy a qubit each, so there are none left over for the method illustrated, which is entangled pairs.

What I meant by random number generation is not the article itself, but the impression it gives Yeatesi, because the article is poorly written. The objective is to improve the article so that readers understand the subject, if one person can see a mistake, then many people can.

The primary commercial application of the subject is cryptography, most of the articles readers, but not all, would associate cryptography with computer software, but it's definition is wider, here is the first part of the cryptography article

Cryptography (or cryptology; from Greek κρυπτός, "hidden, secret"; and γράφειν, graphein, "writing", or -λογία, -logia, "study", respectively)[1] is the practice and study of techniques for secure communication in the presence of third parties (called adversaries).[2] More generally, it is about constructing and analyzing protocols that overcome the influence of adversarie...

When this article is further along, we will have something to summarise into that article. Penyulap ☏ 22:31, 13 May 2012 (UTC)

Are you thinking to cut down the more technical bits of the article or simply clarify them? Frankly, it gets a bit too terse at the end for me but I'd like to hear opinions before I do anything drastic. Skippydo (talk) 13:31, 15 May 2012 (UTC)

I wasn't trying to remove anything myself as there is no shortage of room, and there is no shortage of different kinds of readers for the article. But, if you look at my contributions you'll see I'm not big on deleting things :) But I am friendly and happy to offer my help and assistance. I was a bit bored and lost interest in fixing the article up a little further as far as an approachable overview went. I can't see anyone who would object to you doing as you please, as nobody commented on my radical changes. Generally with an article in a poor state it's good to go, unless it's the tooth fairy, at least the subject of this article keeps some people away :) But if you need any OR or POV or BLP pushing I can help out there, you need only ask :) I think a good diagram would be helpful, I'm into drawing things lately, and pimping the pics here is easy enough that's for sure. Penyulap ☏ 16:05, 15 May 2012 (UTC)

Recent edit

Let's just go line by line...

While quantum bits (qubits) used in QT are sometimes compared to regular binary bits, they do not contain information such as a zero or one, they contain what may be considered a random piece of information.

The state is not random. A quantum state is only distinguished from a binary state based on the space of states, a Hilbert space vs {0,1}^n in this case.

The information has no defined state until the state is created by reading the bit, however the qubit can be manipulated, transmitted, split, and linked to another qubit prior to it having a defined state.

It always has a well-defined state, see the previous comment.

When two halves of a qubit are transmitted to distant locations, reading the bit in one location will cause both halves to choose the same state at the same time, regardless of the distance between them.

Qubits do not have halves, they are indivisible units. You likely mean two distinct qubits which are entangled.

If the transmission of a qubit stream was observed or interception by a third party prior to its intended destination, it would destroy the qubits, interrupt the transmission of information, and would be apparent to all parties, thereby providing a unique level and type of security.

They are not destroyed, the qubits take on a state depending on the initial state and the measurement basis. If the qubits are transmitted using a known orthogonal basis, they can be easily read by a third party. Skippydo (talk) 20:28, 21 May 2012 (UTC)

cool, can you help with new approachable language for the lede, suggesting alternatives would be a great help. Penyulap ☏ 20:42, 21 May 2012 (UTC)

At the moment, the intro is concise and technical. Is there anything that isn't mention that should be? Is there anything that should changed to less technical language? Skippydo (talk) 00:48, 22 May 2012 (UTC)

Here I've summed up the parts we need from wp:mosintro

The lead section should briefly summarize the most important points covered in an article in such a way that it can stand on its own as a concise version of the article. It is even more important here than in the rest of the article that the text be accessible. In general, specialized terminology and symbols should be avoided in an introduction. Mathematical equations and formulas should be avoided when they conflict with the goal of making the lead section accessible to as broad an audience as possible. Where uncommon terms are essential, they should be placed in context, linked and briefly defined. The subject should be placed in a context familiar to a normal reader. For example, it is better to locate a town with reference to an area or larger place than with coordinates. Readers should not be dropped into the middle of the subject from the first word; they should be eased into it.

So basically the objective as I see it is to explain it to anyone. So, phrase by phrase, we need accessible wording for "the space of states", or something close enough to the concept to be an uncontroversial summary or description. "It always has a well-defined state", can we find a way to describe the state ?

Qubits do not have halves, they are indivisible units. You likely mean two distinct qubits which are entangled.

Well my mistake there, yes, the two qubits function as a single item in the stream, I probably was getting towards a classic bit there, but an entangled pair sortof needs an explanation of entanglement, pair is good, or I'm not sure, maybe just "each item in the stream is a qubit pair and is used to create the one classic bit at both destinations". classic needs only five or six words to explain.

They are not destroyed, the qubits take on a state depending on the initial state and the measurement basis. If the qubits are transmitted using a known orthogonal basis, they can be easily read by a third party.

Ok they can be read, yes they take form, I mention that, but is it not true that this is detectable, and that QT can be applied in the field of security, how would you include that in the wording, and if we use the phrase "orthogonal basis" it needs to be explained somewhere, it's not in the article and is not approachable. Penyulap ☏ 01:56, 22 May 2012 (UTC)

For space of states, I suggest we simply observe that a bit has two states whereas a qubit has infinitely many states. A canonical representation of the possible states or anything about measure meant might be too much for the intro. I don't see what security has to do with this article. Skippydo (talk) 14:43, 22 May 2012 (UTC)

I can go with that, I don't really think it's applicable at the application level however, as they are simply trying to read it as a binary state but it is still a step up from what we had and is approachable that's for sure.

On security I can hold back on that one if you want, I figure build a doorway into the article for editors and they will use it. Security is in the external links already, I had figured to include it in the lede initially to compliment the 'you can't use qt for matter'. Maybe just using the same external link as a ref do you think ? I was hoping to be lazy enough to avoid some of the work, I like to do enough to allow many other editors access to the article, put up a framework or make a colouring in book that other people can colour in like here I can add a section either way, I've probably waffled on so long it would have been easier to do so :) shot myself in the foot there on economy. Penyulap ☏ 16:42, 22 May 2012 (UTC)

Professor Nicolas Gissin

This guy is shown on an episode of Through the Wormhole alongside two laser beams, claiming that the photons are entangled and the laser beams act the same. He's even in the references section of this article as N. Gissin. Can someone follow up on this for me please? 67.183.31.46 (talk) 23:37, 11 June 2012 (UTC)

EDIT: oh sorry, I paused it before it got to the correct person, it was physicist John G. Cramer of the University of Washington who was shown. 67.183.31.46 (talk) 01:59, 12 June 2012 (UTC)

Clarification about qubit destruction

The article currently states "Alice applies a unitary operation on the qubits ac and measures the result to obtain two classical bits. In this process, the two qubits are destroyed." What is it specifically that destroys the qubits - the unitary operation or the measurement? Or are those the same thing? 98.203.242.147 (talk) 22:10, 21 August 2012 (UTC)Nydoc

The measurement is what eliminates the information about the quantum state. The unitary operation can be undone, restoring the quantum state. Does that clarify things for you? Skippydo (talk) 17:28, 22 August 2012 (UTC)

That does, thank you! I was thinking of a more complicated procedure to for quantum teleportation, but now I doubt that it would work. This is how I had written it out:

Alice wishes to transmit a qubit to David. Alice has two other qubits which are entangled with qubits posessed by Bob and Carol, respectively. David also has two qubits which are entangled with qubits possessed by Bob and Carol, respectively.

1)Alice applies a unitary operation among all her qubits so that both of her entangled qubits contain information about the qubit she wishes to transmit.

2)Bob and Carol then each performing projective measurments on both their qubits and communicate the results to David as classical bits. David's qubits are now entangled with Alice's qubits.

3)Alice then performs projective measurements of her qubits so that David's qubits will become entangled with each other.

4)David then measures his qubits and applies a unitary transformation that depends on the classical bits he obtained from Bob and Carol.

Would this allow David to have a re-creation of Alice's transmission qubit without ever having communicated with her?98.203.242.147 (talk) 19:40, 23 August 2012 (UTC)Nydoc

Something like what your describing should be possible. But without carefully working out the details, I can't say for certain. Skippydo (talk) 21:01, 23 August 2012 (UTC)

The crux of my scheme is whether Alice is required to transmit any classical bits, or if that can be avoided with some clever entanglement swapping. If it can be avoided then there are some rather interesting applications.98.203.242.147 (talk) 05:02, 24 August 2012 (UTC)Nydoc

It's impossible to signal using entangled qubits, so Alice needs to transmit some kind of information. It should be a fairly straightforward proof as well. Skippydo (talk) 15:56, 25 August 2012 (UTC)

Skippydo seems to be thinking of the no-communication theorem. Re "destruction of qubits" please be very careful about your language, as the no-deleting theorem may apply; it states that (single) qubits cannot be destroyed (although they may seem to disappear when you've got a bunch of shit mixing at once. etc.). User:Linas (talk) 20:22, 20 November 2013 (UTC)

broken link notification

The Bennet et al link doesn't work anymore — Preceding unsigned comment added by 171.65.13.171 (talk) 18:24, 14 September 2012 (UTC)

fixed Skippydo (talk) 17:05, 15 September 2012 (UTC)

Simple English?

Any chance of this article getting Simple English? Would be great for a lot of kids! — Preceding unsigned comment added by 31.223.162.50 (talk) 07:59, 17 April 2013 (UTC)