Talk:Superluminal communication

Using qubits for superluminal communication

I'm probably missing something here, but it seems to me that you really could use qubits for superluminal communication. The article says:

"If Alice wishes to transmit a "0", she measures (...), collapsing Bob's state (...). To transmit "1", Alice does nothing to her qubit."

But I was thinking, instead of just measuring or not measuring, couldn't Alice measure one qubit to transmit a 0, and measure a different qubit to transmit a 1? It could go something like this: Alice and Bob create a state which is an entanglement of three qubits. Then, after it's created, Alice keeps the first and third qubit. Bob takes the second qubit and goes to some far-off distance. So now:

Alice has $|\psi \rangle _{A}$ and $|\psi \rangle _{C}$
Bob has $|\psi \rangle _{B}$

Then, to transmit a zero, Alice performs a measurement on only $|\psi \rangle _{A}$ , and leaves the other two qubits alone. To transmit a one, Alice performs a measurement on only $|\psi \rangle _{C}$ . Then, after Alice performs her measurement, Bob measures $|\psi \rangle _{B}$ . The three-qubit state could be initally set up so that:

$|\psi \rangle _{A}$ has a high probability (greater than .5) of being measured as $|0\rangle$
If $|\psi \rangle _{A}$ is measured as measured as $|0\rangle$ , then, subsequently, $|\psi \rangle _{B}$ has a high probability of being measured as $|0\rangle$
$|\psi \rangle _{C}$ has a high probability of being measured as $|1\rangle$
If $|\psi \rangle _{C}$ is measured as measured as $|1\rangle$ , then, subsequently, $|\psi \rangle _{B}$ has a high probability of being measured as $|1\rangle$

There would be a probability of error in the transmission, but this error would be less than .5. One could compensate for that error by using many sets of three qubits to transmit each bit. Or maybe one could compensate with classical error-correcting codes.

Would all of that work? I'm guessing that I've missed something, since I'm not an expert on quantum mechanics. Most of what I know is from taking a one-semester class on quantum computing. --Navigatr85 03:10, 22 August 2007 (UTC)

The example

If Bob creates copies and measures them, wouldn't they all have the same spins on each axis? Conversely, how is Bob measuring one of his copies different from Alice measuring her copy?

Contradiction with No-cloning theorem

The page for no-cloning theorem states "The no cloning theorem does not prevent superluminal communication via quantum entanglement, as cloning is a sufficient condition for such communication, but not a necessary one", yet this page says that it does. Who is correct? J0lt C0la (talk) 22:42, 4 October 2009 (UTC)[reply]

A thought experiment – using entanglement

A suggestion for a communication system using quantum entanglement:

A(lice) and B(ob) are measuring corresponding particles from pairs of quantum mechanically entangled photons - so-called Bell-couples.

The distance between the transmitter and the source are suitably much shorter than between the source and the receiver, so with synchronized watches the transmitter will detect its twin particle before the other twin reaches the receiver. The transmitter can change its measuring setup by inserting a mirror or not – choice situation, T (1) or T (0). It keeps its choice for an agreed period – for instance 1 / 300.000 sec. The receiver has a fixed preset setup. It should by measuring its part of the pairs with at least 99% probability, guess the Transmitters choice.

As the exchange between the entangled particles takes place instantaneous it will for a growing distance between A and B create superluminal communication.

A suggestion for transmitter and receiver - gives problems UChr (talk) 18:55, 5 June 2011 (UTC)[reply]

It occurs to me that in the example method provided allows the direct transfer of information at superluminal speeds. However, the separation of the entangled pair itself cannot occur at superluminal speeds (pending results allowing the acheivement of FTL, which would render the need moot anyways). Thus, if one takes into account the amount of time needed to establish the communication channel, that being the time to separate the particles, can it be reworked to show that it would still be capable of making up the lost time? Ahroun (talk) 19:31, 27 May 2011 (UTC)[reply]

I do not fully understand your question so I answer a little widely: Exchange itself / 'communication' between two entangled photons assumed by most to be almost immediate / very much faster than the speed of light. In my proposal takes the transmission of one bit - a 0 or a 1 - 1 / 300000 sec. The separation between A and B should therefore be longer than 1 km - 2 km, for example - to send a bit of information at this way. The source should be located approximately in the middle - ie by around 1 km to both A and B - a little longer when you have to receive - but the route can then be extended by inserting some mirrors. The source should start to produce entangled pairs of photons in advance so they arrive at A and B continuous at the appointed time when A wants to send a bit of information to B. If you want to send for example 100 000 km - it would probably take years to get placed source, receiver and transmitter and test it. A practical application - if it works - is a part in the future. The basic ideas can be tested in a lab. UChr (talk) 16:32, 1 June 2011 (UTC)[reply]

Dispute with anon over references

This is getting a bit ridiculous anon188. Most of your challenges to the references are irrelevant or misplaced. In the last edit summary you gave the following as reasons: "Pop science webpage with no content, non-peer reviewed document. Extraordinary claims (sending information back in time), advertising, conflict of interest." Let me address them, though not in the same order:

Extraordinary claims - no, no extraordinary claims are being made. The claim in the contested sentence is that Cramer is pursuing research on this question. No claim is being made whether or he will be successful nor why or why not. No claims about extraordinary physics is being made - that would require a reliable source of the highest quality. But this again is a claim about what research Cramer, a noted and mainstream physicist, is pursuing. Thus the newspaper article is a valid RS for this very ordinary claim
Pop science webpage - no, it is a mainstream newspaper article, a valid WP:RS. See WP:NEWSORG.
non-peer reviewed document - it probably did go through some editorial oversight so it's not just a crank posting on the web, but again, the contested edit is not making a scientific claim, just a claim that Cramer is doing research along these lines
advertising - I fell to see how the edit and ref run afoul of WP:NOTADVERTISING nor WP:RS. Perhaps though I'm missing your argument. Where do you see the reference with respect to advertising going against WP policies?
conflict of interest - don't see how the edit or the reference violate WP:COI. I've no connection with Cramer or his work and research.

Additionally, I would argue that information from Cramer's own webpage on the UW servers as well as the CENPA internal report are valid sources for stating what kind of research Cramer is doing. I don't see this as violating WP:SPS. If instead we were using these sources to support the claim new physics and real superluminal communication, then there would be problem. But again, that's not the claim being made, just that a notable physicist is pursuing legitimate research in the subject. The situation is vastly different from extraordinary claims and self-published references you were pushing on Faster-than-light and elsewhere. --FyzixFighter (talk) 17:11, 12 July 2011 (UTC)[reply]

Additionally - two points. First, the ref in question has nothing to do with the sentence: "As the quantum eraser experiments rely on a classical, subluminal channel for coincidence detection, it is unclear whether superluminal communication would be possible by this method." So why do you keep removing it with your reverts? Second, if you (anon188) are the same as the other anon user (92.20.54.53) and User:FyzixFighter2, you should probably change that last username via WP:CHU based on WP:IMPERSONATOR. --FyzixFighter (talk) 19:17, 12 July 2011 (UTC)[reply]

"FyzixFighter" does not take heed to his/her own standards of the need for properly peer reviewed material. This doesn't include internal university reports (which often have no context, background, citations, survey too) or pop science newspaper items. He or she is looking mentally unhinged and seem to have some connection to the University of Washington or the research and thus this is a conflict of interest. A history of "FyzixFighter" shows this behaviour and numerous cautions/reprimands and a formal complaint will be made. Their actions are compromising the peaceful collective of Wikipedia and amount to trolling. People in numerous countries have noticed such on this article and others. — Preceding unsigned comment added by 188.29.157.237 (talk) 20:49, 13 July 2011 (UTC)[reply]

Yeah...um...wow. I would advise you please read WP:NPA and WP:AGF. As I said before I have no connection (at least none that I'm aware of) with the University of Washington or the research or Cramer (although I have read one of his sci-fi novels) so there is no conflict of interest. You didn't address any of the points I brought up above, but let me reiterate. If the sentence we are disputing over were a definitive statement that Cramer has shown that he has demonstrated superluminal or retrocausal communication, then I agree that we would need a peer-reviewed academic source. However, that is not what the sentence is asserting. It is asserting a simple, non-extraordinary fact that Cramer is conducting research on this subject. From WP:IRS: "Mainstream news reporting is generally considered to be reliable for statements of fact". Since it appears that you are unfamiliar with wikipedia policies and goals, you could ask for community input at various noticeboards (WP:COIN,WP:RSN...) to resolve your concerns. --FyzixFighter (talk) 04:48, 14 July 2011 (UTC)[reply]

"FyzixFighter" has finally calmed down and realised that the rules they apply to other people's edits apply to them. It is a feature of the adult world that we cannot get what we always want, lest one be accused of narcissistic, socio-pathic tendencies.

"FyzixFighter" views reports of work as worth listing. Singular reports be damned! Tenure-ship is no guarantee of freedom from crankdom and that is why there is the peer-review process. Right now, reasonably respectable professors, worldwide, have pet theories or hobbies in sci-fi writing, pigeon poisoning or cat strangling and we can only view these as eccentricities. A sad fact is that these quirks get worse with age... It is vital that a quorum is made, especially for wilder speculations. Even some hint of a respected career and high office is no measure. — Preceding unsigned comment added by 188.29.157.237 (talk) 08:21, 14 July 2011 (UTC)[reply]

May I just add, Jimmy Walsh is an Objectivist and one would do well to read Atlas Shrugged and the sections on the "State Science Institute", then take a look at the peer review process... The university system is a centralised (as in centralised planning), socialistic, monopolistic system which is self serving. Compare the Belle Epoch and the time of the Wright Brothers, Edison, Tesla and more, and compare it with today...

The edits were done in all irony to illustrate how the peer review process kills off new ideas or restricts them to a (usually state funded) clique. You are obviously keen on pushing science forward. Yes we need quality to push out cranks and to stop wasting time and money going down the wrong avenues. The removal edits on the speculative FTL, SL and NC articles illustrate how the status-quo crushes new ideas so that they get no refinement and honing by other minds. You have just taken part in the psychology of a process stultifying science and I thank you for the experiment in human nature. May you have the system and the science you deserve. — Preceding unsigned comment added by 188.29.157.237 (talk) 11:03, 14 July 2011 (UTC)[reply]

FYI... Ed can you block "FyzixFighter" as he has removed a perfectly reasonable edit to the superluminal section bringing in the relevance of general covariance/Relativity, the no-communication theorem and discussion about the speed of quantum decoherence (and a great reference too). I cannot see what this person is up to wilfully vandalising entries for no reason. I think it is apparent now who has the problem. This editing is petulant and demonstrates an intolerance to other people's academic input such that I am convinced now that there are COI issues here. Personally I am finding this person obnoxious and a borderline sociopath. Please release the block and block "FyzixFighter" instead, if there is any fairness. They did it without even any debate. "FyzixFighter's" history shows this behaviour.188.29.157.237 (talk) 22:29, 14 July 2011 (UTC)[reply]

The nonsense talked about time travel and sending information to the past

I dispute that I am getting pointy. There is no consensus and FyzixFighter has merely used pull in going to the editor of this section to lodge a complaint (get yours in first eh?) to prevent his contributions being taken down.

I dispute this sending information back in time nonsense. Wave-function collapse is clearly fast; check the work of Zurek at Los Almos Science. Clearly communication by entanglement would not be Lorentz invariant.

Extraordinary claims - show that someone is sending information from the future to the present. Citing a non-peer reviewed article in something that is seen as an encyclopaedia only puts about the myth in people's minds of this science-fiction science that time travel to the past is possible. The Lorentz transform only applies to light speed limited signals. It is a misuse of mathematics and an exercise in taking things too literally.188.29.157.237 (talk) 14:24, 14 July 2011 (UTC)[reply]

FyzikFighter in their petulance actually knocked out a very relevant reference: Zbinden, H.; Gisin, N., et al, Testing the speed of ‘spooky action at a distance’. Nature, 2008. 454. This should be included somewhere, probably near the bit on Cramer and general covariance. We are trying to stress that collapse IS a very fast process. — Preceding unsigned comment added by 188.29.157.237 (talk) 18:29, 14 July 2011 (UTC)[reply]

I removed that reference because the way it was being used constituted original synthesis. As the Zbinden article is about "spooky action at a distance" as opposed to "spooky communication/signaling at a distance", which the quantum paragraphs in this article are about, it's not clear to me the relavance without getting into original synthesis. Can you give an example of the sentence(s) you would like added with the Zbinden source as a reference, and where in the article it would go? --FyzixFighter (talk) 22:29, 14 July 2011 (UTC)[reply]

"spooky action at a distance" is part and parcel of "spooky communication/signaling at a distance" because it refers to the same process, correlated collapse of the wavefunction. This is not even semantics but obfuscation.

You also removed the sections on General covariance, Relativity, no-communication theorem, quantum decoherence which would, perhaps, not show a deep understanding of the subject matter? None of this is original research but part and parcel of what anyone in the field would know.188.29.157.237 (talk) 22:53, 14 July 2011 (UTC)[reply]

FTL communication

I may be wrong, but is there any reason why a simple non elastic string stretched between point A and B couldn't transmit signals from A to B and back, faster than light? If an observer as A is to send a message to an observer at B it wold push the string, the movement wold be seen immediately by the observer at B so we can assume a signal to propagate faster than light. — Preceding unsigned comment added by 2.82.203.179 (talk) 12:57, 30 March 2012 (UTC)[reply]

See this Physics Forum FAQ post for an explanation why this cannot lead to FTL communication. --FyzixFighter (talk) 07:20, 11 April 2012 (UTC)[reply]

Possibly Relevant Experiment

I'm no expert, but the following would seem to have some bearing on this subject.

(ISNS) -- Researchers working at the Clarendon Laboratory at the University of Oxford in England have managed to get one small diamond to communicate with another small diamond utilizing "quantum entanglement," one of the more mind-blowing features of quantum physics... BobbyBoykin (talk) 20:11, 26 April 2012 (UTC)[reply]

Observed/Unobserved considered Information?

This article seems to imply that quantum nonlocality is not feasible for FTL communication since the spin state of the first entangled particle is unpredictable and therefore cannot be used to meaningfully transfer data in the form of spin state to the second particle, even though this interaction has been observed to occur faster than light could travel between the particles. But isn't the fact that the first particle was observed information in and of itself?

Couldn't a system of binary communication be theoretically accomplished by using observed/unobserved as the binary states instead of spin direction? —Manicjedi (talk) (contribs) (templates) 17:03, 16 January 2013 (UTC)[reply]

Except how does one know, with just access to the second particle, if the first particle was observed or not? For example, if one measures the spin direction of the second particle as down (or up) how does that indicate whether the other person has observed the first particle or not? The closest thing to what you suggest might be a type of Quantum eraser experiment (see refs 4-6) where the placement of one detector effects whether or not the other detector sees an interference pattern. But that also is supposed to require a classical, subluminal channel for correlation detection. --FyzixFighter (talk) 18:13, 16 January 2013 (UTC)[reply]

Okay that makes sense, thanks for the explanation. -—Manicjedi (talk) (contribs) (templates) 20:56, 16 January 2013 (UTC)[reply]

Birgit Dopfer's Experiment

Hi all! Here is a discussion about Dopfer's experiment. Please, if you are able, improve the paragraph. 84.114.197.3 (talk) 17:23, 16 February 2014 (UTC)[reply]

Gravity??

Anybody concerned himself/herself with gravity on this one?? Gravity does in fact propagate instantaneously to within our ability to measure it as per Tom Van Flandern's website; seems obvious enough that any time you take three steps you're sending some sort of a gravitational message out into the void in real time, i.e. a whole lot faster than C. — Preceding unsigned comment added by Swolf46 (talk • contribs) 02:52, 26 February 2014 (UTC) Gravity doesn't propagate instantaneously, but at the velocity of light. See: Gravitational wave.[reply]