Indistinguishability At A Distance

Valerio Scarani

Published Jan 5, 2006• 0 citations

Abstract

Abstract During my first lecture at Saint-Michel College, I had sidestepped the question about randomness that the student had asked. As the reader will recall, it was the experiment of Fig. 1.1, as simple as it was, in which the particles arrived one after the other at a beam splitter. I had said that we do not know how to describe the behaviour of each particle, we do not know why a given particle is reﬂected rather than transmitted. Is it really uncertain, ran- dom (which is the current opinion among physicists) or is there a mechanism yet to be discovered? I had deliberately turned attention from this problem, in order to concentrate on the experiment of Fig. 1.3, the Mach–Zehnder interferometer. We have seen, then, that quantum randomness is a curious randomness – if we assemble two ‘randomness generators’ (beam splitters) in a certain way, we rediscover the certainty! I brieﬂy remind the assembled students of this, a week later, in the old granary of the College.

DOI: 10.1093/oso/9780198570479.003.0006

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