Talk:Quantum pseudo-telepathy/Archive 1

Suggestion

Suggestion: If someone constructed two 3x3 grids and then filled them out in an animated gif then it would make a great picture (for dyk?) and illustrate this fine article. Victuallers (talk) 12:48, 29 November 2008 (UTC)

Bad Math?

For the simple 3X3 square shown, it is true that the rows multiply out to +1 (Row 1 for example is: $+1\times +1\times +1=+1$) and the columns multiply out to -1.

However, how does that work for the Mermin-Peres magic square? For example, how does the product of Row 1: $+S_{x}\otimes I\times +S_{x}\otimes S_{x}\times +I\otimes S_{x}$, equal +1 (or the unit matrix)?

I get $+S_{x}\otimes I={\begin{bmatrix}0&1\\1&0\end{bmatrix}}\otimes {\begin{bmatrix}1&0\\0&1\end{bmatrix}}=\left({\begin{array}{cc|cc}0&0&1&0\\0&0&0&1\\\hline 1&0&0&0\\0&1&0&0\end{array}}\right)^{[1]}$ and $+S_{x}\otimes S_{x}={\begin{bmatrix}0&1\\1&0\end{bmatrix}}\otimes {\begin{bmatrix}0&1\\1&0\end{bmatrix}}={\begin{pmatrix}0&0&0&1\\0&0&1&0\\0&1&0&0\\1&0&0&0\end{pmatrix}}$ and $I\otimes S_{x}={\begin{bmatrix}1&0\\0&1\end{bmatrix}}\otimes {\begin{bmatrix}0&1\\1&0\end{bmatrix}}={\begin{pmatrix}0&1&0&0\\1&0&0&0\\0&0&0&1\\0&0&1&0\end{pmatrix}}$

The product of these three 4X4 matrices is not +1. (Note 1: the partitioning is just to show how the 4X4 matrix is constructed, with the Kronecker Product)

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You are right, but...

${\begin{pmatrix}0&0&1&0\\0&0&0&1\\1&0&0&0\\0&1&0&0\end{pmatrix}}\times {\begin{pmatrix}0&0&0&1\\0&0&1&0\\0&1&0&0\\1&0&0&0\end{pmatrix}}\times {\begin{pmatrix}0&1&0&0\\1&0&0&0\\0&0&0&1\\0&0&1&0\end{pmatrix}}={\begin{pmatrix}1&0&0&0\\0&1&0&0\\0&0&1&0\\0&0&0&1\end{pmatrix}}$

which is the 4X4 unit matrix $I$. All three rows have the same product. All three columns, however, have the product $-I$.

Weird, huh? - you can't do this with numbers, but you can do it with complex matrices!

Spooky action at a distance, 'real'

The third paragraph currently reads as:

"The phenomenon of quantum pseudo-telepathy is mostly used as a powerful and explicit thought experiment of the non-local characteristics of quantum mechanics, referred to by Albert Einstein as “spooky action at a distance”. Yet, the effect is 'real' and subject to experimental verification, as demonstrated by the experimental confirmation of the violation of the Bell inequalities."

I think that it is unnecessary to quote Albert Einstein's distaste for non-locality in every single mention of it. I think that can be dropped, as it is mentioned in detail in the Quantum Entanglement article. Additionally does 'real' really need to be in quotation marks here? The effect is actually a real phenomenon. I am going to remove the offending text. Paul Ganssle (talk) 03:44, 27 December 2008 (UTC)

Too esoteric

I'd recommend "dumbing down" the intro some so that the average reader, or even a school kid, might get a better idea of what the article is about. Boston (talk) 03:21, 4 December 2008 (UTC)

Agreed. I found this via "Did You Know" on the Main Page. I cannot make heads or tails of it. No knowledge on the part of the reader should be assumed. --Nricardo (talk) 03:39, 4 December 2008 (UTC)

I have no idea what this article is about. Too bad its on the front page in DYK.60.53.236.225 (talk) 04:28, 4 December 2008 (UTC)

I'm pretty sure there is a tag that addresses situations like this but I don't know it. Boston (talk) 05:14, 4 December 2008 (UTC)

What this article needs is a statement along the lines of "this will not happen in the real world because..." Or maybe it will, in which case that needs to be said. --NE2 07:18, 4 December 2008 (UTC)

Amen. I have no idea how you would put two macroscopic players into an "entangled quantum state", and I have the faint feeling that the same laws predicting the "entangled behaviour" of the scenario will forbid its creation. -- Syzygy (talk) 07:48, 4 December 2008 (UTC)

I agree about simplifying the article. As it stands, I'm left asking: is this article real or a joke? --Robinson weijman (talk) 08:02, 4 December 2008 (UTC)

• I would not say the article should be simplified. I would suggest instead a basic introductory sentence or two that a layman could comprehend. Boston (talk) 10:48, 4 December 2008 (UTC)

Ok, folks: 1) the effect is real. 2) Yes, this will happen in the real world. 3) Although Quantum pseudo-telepathy has not been tested directly, the violation of the Bell inequalities (of which QPT is a consequence) have been verified experimentally. 4) Quantum entanglement of macroscopic players is not required, it suffices for the players to have access to entangled quantum system no matter how small. 5) Good to see that soo many people are flabbergasted and confused. Quantum mechanics is weird. Will try to include some of the above in the article in the next few days. JocK (talk) 18:43, 4 December 2008 (UTC)

Yes, Boston, that is what I meant - well stated. Any volunteers? --Robinson weijman (talk) 19:47, 4 December 2008 (UTC)

Further clarification - I think a "layman" should be able to understand the article without reading any other articles. As it is, I think I need to read a number of other articles (e.g. Quantum entanglement before I have a clue what it is saying. --Robinson weijman (talk) 17:24, 5 December 2008 (UTC)

You don't mean the entire article, I assume? Given that the nature of the phenomenon is something that a layman is unlikely to understand, I think it would be better to write it as if the reader has read other articles on quantum mechanics with an introduction that conveys the gist. I don't think it's a good idea to sacrifice content in an inherently complicated topic just to make the article self-contained. The way I read the article I think that it's fairly well-written and conveys the gist of the concept very well. Though I have to say I have some trouble understanding the nature of the magic square game that is mentioned. It sounds to me like the article says that there is NO solution to the game (i.e. no grid which satisfies the requirements), and I don't see any mechanism for scoring the game (in terms of non-optimal solutions). Maybe this is what is creating the confusion and the poor understanding of entanglement is masking this? Paul Ganssle (talk) 03:50, 27 December 2008 (UTC)

information transfer

So can you transfer information via quantum entanglement or not? 24.137.73.33 (talk) 04:09, 4 December 2008 (UTC) and does this occur at faster than light speeds? 24.137.73.33 (talk) 04:11, 4 December 2008 (UTC)

Good question, needs to be addressed in the article. The quick answer is: no you can not transfer information via quantum entanglement. What quantum entanglement can do is to reduce the amount of information required to acomplish certain tasks. A subtle difference... JocK (talk) 18:46, 4 December 2008 (UTC)

Question

I'm no expert, but isn't the caption ->

When attempting to construct a 3x3 table filled with the numbers +1 and -1, such that each row has an even number and each column an odd number of negative entries, a conflict is bound to emerge.

wrong? Since rows are horizontal and columns are vertical, shouldn't that statement be switched? —Preceding unsigned comment added by Pbroks13 (talk • contribs) 04:23, December 4, 2008

No — the table isn't talking about the sum of the numbers, it's talking about the number of times that the negative entry is placed in each row or column. So, in the top row, there are 0 negative entries, and in the middle row there are 2; there is 1 negative entry in each of the first two columns. It might be slightly clearer to say "...such that each row has an even number of negative entries, and each column has an odd number of negative entries" — but I'll leave that change to people with a better understanding of the thought experiment than mine. (I can get this far, but not much further.) —Josiah Rowe (talk • contribs) 05:04, 4 December 2008 (UTC)

FTR

I am apoplectic. Dummy down so a child, presumably one in the famously failed US public grade schools, can understand it. Does this not say it all? Lycurgus (talk) 17:39, 4 December 2008 (UTC)

+ / - In Game

A question about the game - is it necessary for the chosen symbols to be +1 and -1? Could they not as easily be e.g. noughts and crosses? --Robinson weijman (talk) 17:26, 5 December 2008 (UTC)

Any binary choice (1/0, +1/-1, +/-, x/o, red/green, yes/no, ...) will do. The advantage of introducing the choice +1/-1 early on in the article, is that it provides a direct link to the eigenvalues of the spin operators used (and needed!) to 'do the trick'. JocK (talk) 18:20, 5 December 2008 (UTC)

Best of DYK

Whilst on Wikipedia's main page, the 'Did you know...' on Quantum pseudo-telepathy was on average viewed once every 6 seconds.

This, I think, is quite an exceptional result for DYKs linking to science articles. I'm happy :) JocK (talk) 18:33, 5 December 2008 (UTC)

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No Solution?

I've tried every way of doing it in my head, and as far as I can tell, there is no 3x3 grid of -1's and +1's such that there is an odd number of -1's in the columns and an even number of +1's in the columns. The task is not possible, even with communication. What am I missing? --Wingedsubmariner (talk) 06:03, 25 February 2009 (UTC)

Yeah, I don't think there is such a way. Maybe it would be better to just use a 2x2 game like Battle of the Sexes or something? Paul Ganssle (talk) 07:21, 25 February 2009 (UTC)

The Current Research section says that this is the simplest game where this effect is observed, so I don't know if that would work (though it may still make a better example of this kind of game). I feel like there is something in the game description that's missing. I keep trying things, like adding imaginary numbers, and nothing works. Maybe the goal is just to make as many columns and rows hold to the condition as possible. I haven't found anything in the references yet. --Wingedsubmariner (talk) 18:00, 25 February 2009 (UTC)

Well, Alice and Bob aren't asked to fill the whole 3x3 grid. Each time the game is played, Alice is asked to fill a row, and Bob is asked to fill a column. With communication between both players they can inform each other which row/column was selected for them, and with that knowledge the task becomes trivial.

When communication between the players is not possible, we get into an entirely different game. The only way out would be if the two players could agree (a priori) on a full 3x3 grid with the requested properties. However, such a grid does not exist (as confirmed by your remarks above). That is to say: the grid doesn't exist when relying on real (or complex) numbers to fill the grid. Filling the grid with non-commuting elements as entries is another matter. (And quantum mechanics is synonymous to non-commuting mechanics...) JocK (talk) 03:02, 26 February 2009 (UTC)

Ah! I get it now. Thank you. I've made a small change to the description to make it clearer to others. Wingedsubmariner (talk) 00:53, 27 February 2009 (UTC)

?

I do not understand this at all. This is supposed to be a game right? Alice and Bob are the players. Do they play against each other? Against Physics? What? In the game of chess, you win by mating your opponent. When does Alice win? Yes I am for real. I could probably infer this by wading through formulae of the source paper but it does not get clear from reading article --88.75.228.135 (talk) 07:50, 2 November 2009 (UTC)

This is not a game where Alice and Bob compete against each other. They are acting separately (ie, no communication), but producing a result which seems impossible (without communication). The fact that it seems impossible, but it is real, guides a physicist where to question his intuition and try to improve it. The game is that Alice and Bob each have their own piece of equipment which performs measurements on a previously-prepared quantum system. They fill out their 3X3 squares according to the results of their measurements. To each of them, the measurements are random, but an observer who sees both squares can see the 3X3 are related to each other.

English, do you speak it?

"To solve the table simply, the square root of 1, which can be either positive or negative in value, so either option is possible, simultaneously." FAIL. —Preceding unsigned comment added by 76.68.250.165 (talk) 17:50, 3 September 2010 (UTC)

Review external Link

I added an external link to an explanation more in-depth than the article but less technical than the referenced papers. I actually wrote that explanation, so I'd appreciate someone reviewing it for appropriateness as an external link. Craig "Strilanc" Gidney 07:58, 20 October 2013 (UTC)

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— Preceding unsigned comment added by Strilanc (talk • contribs) 07:58, 20 October 2013 (UTC)

This is Alain Tapp course in Quantum Computing:

https://sites.google.com/site/alaintapp/cours/ift6155

There is a pdf on pseudo-telepathy, the only problem is that it is french. Otherwise, it explains quite well the phenomenon. Should we put a link? — Preceding unsigned comment added by 69.165.134.156 (talk) 16:45, 6 July 2011 (UTC)

As there been experimental validation of quantum pseudo-telepathy? please note that quantum pseudo-telepathy isn't the same thing as bell inegalities.... It requires more quantum ressources, among other things. It should be important to write about that, I think. Also is quantum pseudo-telepathy the same thing as spooky communication? Still reading about it... Hopefully I can help with this article in a while. — Preceding unsigned comment added by 70.30.176.87 (talk) 14:55, 25 July 2011 (UTC)

There is no such thing as "spooky communication", that's just an example of Einstein being wrong that journalists love to jump all over. Please don't "help" with this article if you are going to use the standard journalistic approach of "make quantum mechanics sound as weird as it can possibly sound", which nearly deliberately obscures the facts. It's bad enough that this concept is called "quantum pseudo-telepathy". 0x0077BE (talk) 16:17, 20 October 2013 (UTC)

There is also luck

If the participants choose to pick answers randomly they would be the possibility they get it right. Quantum entanglement is not the only way. --TiagoTiago (talk) 05:06, 29 October 2011 (UTC)

Sure, if they just guess, then they can win 50% of the time. But with QE they can win 100% of the time, and that's the point here. Does it need to be explicit? Joule36e5 (talk) 08:28, 19 July 2012 (UTC)

On second thought, it looks as though they can win 8/9 of the time, by pre-arranging a table such as the one shown in the article, with the two players disagreeing on the value for the one square that's in conflict. It now seems to me that if any of the other 8 cells is chosen, then they'd succeed without any quantum effects. Have I got it right, that entanglement increases their success rate (under optimal play) from 8/9 to 1? I think the article should be explicit about the probabilities for the sample game, in any case. Joule36e5 (talk) 08:48, 19 July 2012 (UTC)

As I understand it, it's 100% winning if you do it the quantum way. That's the "miracle".

I did notice the following (actually it is pointed out in the article): If you take the product of the left or right operators in any row, you get I. If you take the product of the left or right operators in any column, you get -I. So if you are allowed to "do" 3 either the left or right operators in a row (or column), you get 3 numbers whose product has the correct parity. But I'm confused about how this helps you, since you don't multiply the operators, but apply them to states and then multiply the numerical results. Also, why would you be able to make 3 measurements on a system without collapsing it 3 times? And where you place the operators (in the expression for expected outcomes) when the other guy is doing the same thing 3 times? Something is wrong here.

See my comments below, where I've resolved most of my other sources of confusion. 89.217.12.73 (talk) 23:23, 29 April 2015 (UTC)

Not enough info

The article is tantalizing, but doesn't give enough information for those who haven't read the original paper to see what's going on. What is the game exactly? Give payoff matrix. — Preceding unsigned comment added by 195.111.2.2 (talk) 08:50, 15 July 2013 (UTC)

It doesn't refer to a specific game, it's a general phenomenon with a misleading name. Basically, in the massively unlikely situation that you need to take a coordinated action with someone in a situation where you cannot communicate with them but you DO have access to an entangled set of particles, you can use those entangled particles to coordinate. It's... not a useful concept, to say the least. Consider that if you are going to maintain particles with an entangled state, you might as well just give someone a flash drive with 16 GB of random numbers on it and instructions for generating numbers, words, etc. Then you could win the Magic Squares game easily without having to create an entangled state. This is basically a dumb concept which gets traction because it plays on "quantum weirdness" - which itself is basically the same sensationalist nonsense that went behind naming "imaginary numbers" (a critical math concept which is belittled by its ridiculous name). 0x0077BE (talk) 13:49, 21 October 2013 (UTC)

Having shared random numbers is not sufficient to consistently win the Magic Squares game. There is no classical strategy that consistently wins (assuming no communication during the game, of course). The article already explains why; but if you're not convinced I suggest actually trying to come up with a strategy and playing it out to see why it doesn't work consistently. That's what makes the quantum strategy useful or at least interesting: it wins consistently where classical strategies can't. --User:Strilanc —Preceding undated comment added 20:44, 19 November 2013 (UTC)

Horrible choice of symbols in the first equation

It uses + both for "the cell has a +1 in it" and "addition of two quantum states". Unless you're already familiar with the bra-ket notation, the equation actually hinders your ability to understand it. Jaysbro (talk) 16:09, 14 November 2013 (UTC)

If you are not familiar with bra-ket notation, you can't understand it. QM is not something you can understand by casually skimming WP articles. 67.198.37.16 (talk) 16:09, 2 November 2016 (UTC)

Non-technical Mermin-Peres Explanation

The Mermin-Peres game was critiqued as too technical for a non-expert, so I added a paragraph that I believe will allow a non-expert to better appreciate what is happening. I am unsure if what I did is sufficient, but here's a heading to discuss it. Scott Bowden (talk) 16:14, 2 June 2014 (UTC)

Looks good to me, I am removing the tag. It's hard to guess why someone thought it was too technical. 67.198.37.16 (talk) 16:06, 2 November 2016 (UTC)