## Wednesday, May 18, 2011 ... /////

### David Mermin's talk: Why Einstein was wrong

In 2008, David Mermin gave an Oppenheimer lecture at UC Berkeley which was called "Spooky Action at a Distance?" (PDF form here).

It's a nice presentation why there is no "reality" as imagined by Einstein and others. Mermin explains why Bohr was right when he said that we have to be cautious and only talk about things that can actually be measured - avoid assumptions that something else exists.

Physics is not a tool to describe how the reality is. Physics is a tool to say right things about what we can see. A big difference.

An important part of his demonstration are gedanken experimental proofs :-) which are shown on the screen but in principle, they could be shown in tabletop experiments as well. The screen is more convincing because the unnecessary wires are removed. You just have to believe that he is not lying about the outcome of the experiments.

Mermin, whose viewpoint on quantum mechanics has been praised by Feynman and who is also the actual father of the "Shut up and calculate" dictum, is one of the people who localized the special, non-realistic behavior that follows from quantum mechanics most accurately.

So he also shows the audience some computer simulation of his gedanken experiments. In that gedanken demonstrations, detectors are able to measure the binary value of one of the two quantities, according to the position of a switch. First, he discusses the "non-existence" of two non-commuting properties, 1-color and 2-color, in the EPR-style setup. Then he presents his optimized version of the GHZ experiment, GHZM.

See also David Mermin on reality and abstractions and his Copenhagen Computation: How I Learned to Stop Worrying and Have Sex With Bohr (I wonder how many extra clicks this small modification of the title added).