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Bell's theorem is a term encompassing a number of closely related results in physics, all of which determine that quantum mechanics is incompatible with local hidden-variable theories, given some basic assumptions about the nature of measurement.
- Ups and Downs
- Local Hidden Variables
- Above The Bound
The “spooky action” that bothered Einstein involves a quantum phenomenon known as entanglement, in which two particles that we would normally think of as distinct entities lose their independence. Famously, in quantum mechanics a particle’s location, polarization and other properties can be indefinite until the moment they are measured. Yet measuri...
Armed with this understanding of spin, we can devise a thought experiment that we can use to prove Bell’s theorem. Consider a specific example of an entangled state: a pair of electrons whose total spin is zero, meaning measurements of their spins along any given axis will always yield opposite results. What’s remarkable about this entangled state ...
Now, what about quantum mechanics? We’re interested in the probability of both labs obtaining the same result when measuring the electrons’ spins along different axes. The equations of quantum theory provide a formula for this probability as a function of the angles between the measurement axes. According to the formula, when the three axes are all...
4 nov. 2014 · Le 4 novembre 1964, l’éphémère revue Physics recevait un article écrit par John Bell, théoricien au CERN. Si la revue en question n’est plus qu’un souvenir, l’article, lui, est devenu célèbre, jetant les bases d’une nouvelle discipline, l’informatique quantique.
23 oct. 2020 · Pour démontrer l’inégalité de Bell, on a besoin de quelques définitions, de quelques lignes de calcul algébrique sans grande subtilité, et d’ UN argument qui contient toute la physique du truc. Je vais vous donner les définitions et l’argument, je vais zapper quelques calculs.
John Bell and his famous theorem in 1982 (Image: CERN) On 4 November 1964, a journal called Physics received a paper written by John Bell, a theoretician from CERN. The journal was short-lived, but the paper became famous, laying the foundations for the modern field of quantum-information science.
4 nov. 2014 · Bell's Theorem - more formally known as 'On the Einstein-Podolsky-Rosen paradox' - demonstrated that Einstein's views on quantum mechanics - the behaviour of very small things like atoms and...
12 nov. 2014 · John Bell faisait partie des rares physiciens qui, tels Einstein et Schrödinger, étaient profondément insatisfaits devant l'interprétation orthodoxe de la théorie quantique, celle dite de...
