Author Archives: Mateus Araújo

Deutsch’s version of the Deutsch-Wallace theorem

With the decision theory from the previous post already giving us probabilities, all that is left to do is add the Many-Worlds interpretation and show that these probabilities must actually be given by the Born rule. Sounds easy, no? But … Continue reading

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Probability from decision theory

There exists a problem in the world, that is even more pressing than the position of cheese in the cheeseburger emoji: namely that nobody™ understands the Deutsch-Wallace theorem. I’ve talked to a lot of people about it, and the usual … Continue reading

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On the morality of blackholing in conferences

Consider the entirely hypothetical situation where you are in a physics conference with really bad wifi. Either because the router has a hard limit in the amount of devices that can connect simultaneously, or the bandwidth is too small to … Continue reading

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Is gravity quantum?

Last week two curious papers appeared on the arXiv, one by Marletto and Vedral, and the other by Bose et al., proposing to test whether the gravitational field must be quantized. I think they have a nice idea there, that … Continue reading

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How quantum teleportation actually works

EDIT: Philip Ball has updated his article on Nature News, correcting the most serious of its errors. While everyone makes mistakes, few actually admit to them, so I think this action is rather praiseworthy. Correspondingly, I’m removing criticism of that … Continue reading

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Pure quantum operations

Everybody knows how to derive what are the most general operations one can apply to a quantum state. You just need to assume that a quantum operation Is linear. Maps quantum states to quantum states. Still maps quantum states to … Continue reading

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What is the probability of an infinite sequence of coin tosses?

It’s 0, except on the trivial cases where it is 1. But clearly this is the wrong way to formulate the question, as there are interesting things to be said about the probabilities of infinite sequences of coin tosses. The … Continue reading

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Crackpots in my inbox

Often people ask me why I’m not more open-minded about ideas that defy the scientific consensus. Maybe global warming is just a conspiracy? Maybe Bell’s theorem is in fact wrong? Maybe the EmDrive does provide thrust without using propellant? Maybe … Continue reading

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My shortest research program ever

\[ t=0:00 \] SIMPLICIO: These quantum gravity people! Always claiming that the world is fundamentally discrete! It’s so stupid! INGENUO: Humm why is it stupid? They do have good reasons to think that. SIMPLICIO: But come on, even the most … Continue reading

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The sleeping beauty problem: a foray into experimental metaphysics

One of the most intriguing consequences of Bell’s theorem is the idea that one can do experimental metaphysics: to take some eminently metaphysical concepts such as determinism, causality, and free will, and extract from them actual experimental predictions, which can … Continue reading

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