Come on, Minecraft does not pretend the implement classical physics.

The problem isn't lack of rigour, is that it gives you the wrong intuition. For example, the essential feature that distinguishes superposition from a classical mixture is that there is a basis in which the result of a measurement is deterministic, and from what I have seen this is not the case in the mod.

One way that it could be done: a "superposition" block, that can be prepared in the states |0>, |1>, |+>, or |->. If you look at it vertically, you measure in the Z basis, and if you continue measuring in the Z basis, the result doesn't change. If you then measure in the X basis, it's gonna collapse randomly to either |+> or |->, and it's gonna keep being this one as long as you keep looking at it vertically.

And this gives you also complementarity, which I think is one of the fundamental quantum concepts. The way the "observation" block was implemented simply makes no sense whatsoever. It's just a block that is different depending on the way you look. There is no complementarity between the aspects of the block, or anything to deal with the randomness of the quantum observation.

I don't understand what are you talking about teleportation. It doesn't sound to me very much related to real quantum teleportation. But I think the trouble with teleportation is that it is actually quite boring, and would serve no purpose in a game.

But it would be nice if we had some "quantum interaction" thingie (a CNOT) that would take two "superpositions" in different basis to an entangled state, and with this entangled state we could run the chsh game or ek91 qcrypto protocol.

Well, you could say that doing a PhD in physics is playing such a game, and, sure enough, most physicists have a working intuition on how quantum mechanics work -- more on the level of given a description of a situation, they can tell more or less what will happen without doing the calculatios. Doing that part is not hard at all. Heck, this kind of intuition mathematicians develop about the most abstract and artificial objects.

But on a more fundamental level, I don't think it is possible to develop a good intuition, because our brains process information classically; we need well defined bits to reason about. But it might not even make sense to be able to reason quantumly, as the essential feature would be preserving the superposition of the systems we interact with. But to preserve the superposition is to have no memory of the interaction, so... it would be very weird indeed.

Try to imagine what a quantum computer would feel as it processes quantum information: it can only apply transformations to its information blindly, without ever reading out what its input actually is, until the very end of the calculation -- and even this final measurement only because we, humans, want it, it's perfectly legitimate to never have a final measurement at all.

I am a physicist, but these are only drunken speculations...

At first I was quite excited with the idea that someone was able to use quantum mechanical elements in a game. But of course, they were not able to do this. They just created a mod vaguely inspired by quantum mechanics, that helps to perpetuate the myths so beloved by the lay media.

The video linked just shows a dude running around, nothing very interesting. If you search youtube a bit, you can find videos talking about the mechanics they implemented. I found this one, about the basic elements -- observation, superposition, and entanglement --, and this one, with the extremely exciting title "quantum computers and teleportation".

Of course, what they call observation and superposition have nothing to do with the quantum concepts, they are just blocks that are different depending on which direction you look at them, and the "entanglement" block is just a glorifed telephone. Their quantum computer doesn't seem to do anything besides teleportation, which is Star Trek teleportation instead of quantum teleportation.

Admitedly, these guys set out do to a terribly difficult task: quantum mechanics is a bit subtle, and quite far from games. The only ones I can remember off the top of my mind are the CHSH game, which is about as exciting as tic-tac-toe, and a quantum strategy to cheat at bridge, which requires you to do a nontrivial amount of maths (and is actually unpublished research =).

They have, nevertheless, failed. The mod looks cool as a game, though.

That's the kind of mentality that leads Firefox to shipping with a different interface every version.

This is completely beside the point (although true). The problem is that the voting system allows for such a thing to happen. Ever wondered why no European democracy has a two-party state? Well, they have sane voting laws. First past the post system without runnofs is just insane. Gerrymandering, electoral college, come on. Once the US was an inspiration to every democracy in the world. Now it has become a laughing matter.

As far as I know the Bristol folks do integrated optics, so it is in fact a chip; not as small as a classical chip, but about the size of a fingernail.

As a side note, it makes me sad that such an awesome project had to taint itself with the mention of Google and NASA waste of millions of dollars to D-Wave. What the Bristol people are doing is quantum computing. What D-Wave is doing isn't.

I don't think the analogy holds. Certainly knowing the details of quantum optics is quite labourious, but doing quantum programming is already some kind of quantum mechanics, that does not reference any particular physical system. Just like a Turing Machine uses Boolean algebra, but does not reference any particular machine to implement it.

Also, it's true that the algorithms are described in purely classical terms, but they probably sound like gibberish if you are not familiar with the concepts. As an example, let me describe you one of the simplest quantum algorithms known, the single-qubit version of Deutsch's algorithm, which decides whether a (classical) single-bit function f is such that f(0)=f(1) or f(0) != f(1):

Initialize your qubit in the state |0>
Apply the Hadamard gate to it
Apply the oracle that calculates f to it; it is described by the operator e^(i pi f(0)) |0>1|
Apply the Hadamard gate to it again
Measure in the computational basis.

I don't think it is particularly hard to understand it, though; if you want to do it seriously, there's a quite good book about the subject: it's called "Quantum Computation and Quantum Information", by Michael Nielsen and Isaac Chuang.

Can you elaborate on that? My laymen impression is that prosecutorial discretion allows you to at any time ignore any law you wish. But to ignore a specific law all the time seems a bit of an exaggeration.

So you'd rather trust a 89-year physicist with no training in climate science than the ones who have actually learned the subject? That's very enlightened of you.

I don't know what you mean by "very skeptical", but wikipedia says he does believe that the planet is warming and it is our fault; he seems to distrust the mathematical models we used to predict the climate.

For whatever it's worth, I am a physicist, and I have never met (personally) a physicist that is a climate change denier.

This sounds cool, but actually doesn't make any sense. The problem is not big endian versus litlle endian. Microsoft could very well use com.microsoft.xbox.360, but then somebody could squat com.xbox.360. Or microsoft could use com.xbox.360, and somebody would try to squat com.xbox360. The advantage of USENET is that its hierarchical structure was more or less well defined, while in the WWW it is completely arbitrary what you put before the .com part.

How the source adds nothing to the discussion? I've seen this on slashdot when the story first appeared, and the media coverage was uniformly believing CERN's hype, without a shred of scepticism. This blog has a simple, correct explanation of the physics involved, and its interpretation of the data pretty much agrees with I've been hearing at the University.

I was not expecting it to be like old stark trek. I was just hoping that this time the plot would make any sense. Clearly I was mistaken.

I did just that. Watched "the wrath of khan" for the first time this wednesday and then watched "into darkness" yesterday. Damm sure this made me dislike "into darkness" more. It's just a rehatch of the "emotional" scenes of "the wrath of khan" without any coherent plot to link them together. While "the wrath of khan" had a plot that made sense, and was thought provoking, this one had... nothing.

I wouldn't mind to see good visual effects and some action scenes in a Trek movie. But why can't they also use a decent script? It's not difficult to find somebody capable of writing a better story then the one that was used.

I don't mean to insult you, but you seem to be talking without having read TFP, which I did. It is here. (Incidentally, this paper just repeats the arguments first published here, but with a better experimental setup.)

I'm saying this because, as the paper says explicitly, the number 10,000 c has nothing to do with resolution of the clocks, but with their choice of preferred reference frame.

And the experiment I had in mind was quantum teleportation, where it is a little bit less insane talking about the "speed of quantum information".

So what you do is to send a quantum state from Alice to Bob. If you do the calculations, they show that quantum teleportation instantly transfers the state from Alice to Bob. But Bob is only capable of acessing the state after A also sends him some auxiliary classical information (two bits, to be precise). That's why I said that the only scientific thing that you can claim is that the information propagates at lightspeed, because before receiving also the classical information no measurement that Bob can do can say whether he received the state or not.

About the subjectivity, I know this is weird, but there dosn't seem to be any way around it. The state that the calculations show changing instantaneously is Alice's knowledge of the spin, which in fact does change as soon as she makes the measurement. But it makes no sense to say that this is also Bob's knowledge about the state of the particle, since he has no idea about what's going on.

This is bullshit. The scientific content behind this claim is that "nonlocal realistic models that reproduce the results of quantum mechanics must have speed of communication at least 10,000 faster than the speed of light in some arbitrary ference frame that we've chosen".

This means that this number is completely irrelevant, i.e., does not measure anyhting related to the real world.

What can be said, scientifically, about the speed of this channel is that it is the speed of light, because we can only actually measure the presence of the information on the other side after a light signal is sent from one party to the other.

The fact that it looks instantaneous is more of an artifact of our mathematical formalism, and a common philosophical misunderstanding about the nature of the quantum state (i.e., people regard it as objective rather than subjective).