The Bethe Lectures - Gordon Baym, University of Illinois at Urbana-Champaign. Refreshments at 3:30pm
Abstract: Niels Bohr once suggested a very simple two-slit diffraction experiment with highly charged particles to prove that, in order to preserve the consistency of quantum mechanics, the radiation field must be quantized (Aage Petersen, private communication). As this talk will describe in detail, measurement of the electric field of the particle, far from the interference apparatus, yields "which path" information, and thus the diffraction pattern must be destroyed. The loss of phase information must occur via coupling to a quantum radiation field.