Published online by Cambridge University Press: 11 April 2011
Respectfully dedicated to the great chef
There is an ongoing series of symposia, at Tokyo, on ‘Foundations of Quantum Mechanics in the Light of New Technology’. Indeed new technology (electronics, computers, lasers, …) has made possible new demonstrations of quantum queerness. And it has made possible practical approximations to old gedankenexperiments. Over the last decade or so have appeared beautiful experiments on ‘particle’ interference and diffraction, with neutrons and electrons, on ‘delayed choice’, on the Ehrenburg–Siday–Aharonov–Bohm effect, and on the Einstein–Podolsky–Rosen–Bohm correlations. These last are of particular relevance for the particular themes of this paper. But those themes arise already in the context of technology which is neither new or advanced, as is illustrated by the following passage:
I want to boil an egg. I put the egg into boiling water and I set an alarm for five minutes. Five minutes later the alarm rings and the egg is done. Now the alarm clock has been running according to the laws of classical mechanics uninfluenced by what happened to the egg. And the egg is coagulating according to laws of physical chemistry and is uninfluenced by the running of the clock. Yet the coincidence of these two unrelated causal happenings is meaningful, because, I, the great chef, imposed a structure on my kitchen.
These notions, of cause and effect on the one hand, and of correlation on the other, and the problem of formulating them sharply in contemporary physical theory, will be the themes of my talk.