Saturday, 4 April 2009

Entanglement and free will

A colleague recently directed me to this paper (arxiv here), about entanglement and its philosophical consequences, by John Conway, of whom I was previously aware as a pure mathematician, and  Simon Kochen. 

The paper considers a system of two entangled spin-1 particles in separate locations, such that the total spin of the particles is zero. The authors assume that the observer (A) of one particle has free will to chose a set of axes in which to measure the squared components of the spin of the particle (i.e., he can make a choice of which axes to chose independent of his past history), and an observer of the other particle (B) has free will to measure the spin of this particle in one direction.  

Furthermore, they assume the observers to be in motion such that A makes his measurement before B in A's inertial frame, but after B in B's inertial frame (temporal order is not invariant in relativity). The authors conclude that if we assume that the choices of A and B are free, then, in the same sense, the particles make a free choice (they give measurements independent of their past histories).

For more details, in addition to the original paper, see the recent notice to the AMS and this explanatory article. Also, John Conway is giving some lectures on the subject, the videos of which are being put online here.

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