Author Archives: Mateus Araújo

The two-envelope paradox

A colleague of mine, Simon Morelli, told me about a fascinating puzzle, the two-envelope paradox: you can take one of two envelopes with money inside them, promised to contain one $x$ and the other $2x$ for some $x > 0$. … Continue reading

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The problem with being your own father

is not really a moral one. In the typical time travel story you were abandoned as a child, so after you travel back in time you don’t even know who is supposed to be your mother. Now what can you … Continue reading

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Meaningful Bell inequalities part 2: examples

Here I’ll show examples of the meaningful Bell inequalities I talked about in the previous post, where they are rephrased as nonlocal games and the gap between the local bound and the Tsirelson bound is made as large as possible. … Continue reading

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Meaningful Bell inequalities

Since I’ve started learning about Bell inequalities, it always bothered me that they are usually present as just some linear combinations of conditional probabilities, without any physical interpretation besides the fundamental fact that the maximal value this linear combination can … Continue reading

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The Choi-Jamiołkowski isomorphism: you’re doing it right

Yes, you are. There’s nothing to worry about. I’m just writing this blog post because there are some people trying to convince you otherwise, and I don’t want you to get trolled by them. First of all, what is the … Continue reading

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A great month for the quantum switch

If you’re a fan of the quantum switch, like me, the arXiv brought two great news this month: first, an Argentinian-Brazilian-Chilean collaboration finally managed to implement a superposition of more than two causal orders, as I had been bothering people … Continue reading

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Boris Tsirelson 1950-2020

Boris Tsirelson died on the 21st of January 2020 in Switzerland, via assisted suicide after being diagnosed with high grade cancer. It is with great sadness that I type these news. I never met him personally, but I appreciate his … Continue reading

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Infinity in Nature?

Last week a bomb landed on the arXiv: Ji et al. posted a proof that MIP*=RE which implies, among other goodies, a solution to Tsirelson’s problem. I’m speaking here as if their proof actually holds; I can’t check that myself, … Continue reading

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scientists4future #unter1000

I just signed the #unter1000 pledge to not fly to destinations that are under 1,000 km away, and I encourage every reader to sign as well. We, scientists, need to set an example. We understand better than most the dire … Continue reading

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Quantum supremacy won me a bet

About three years ago, on 21.03.2016, I made a bet with Miguel Navascués. At the time superconducting qubits were in their infancy: devices based on them had very few qubits, and quite shitty ones at that. Nevertheless, I was sure … Continue reading

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