Dirac Medallist 1995

Michael Berry, University of Bristol, UK

for his discovery of the non-integrable phase that arises in adiabatic processes in quantum theory. This effect was first detected in 1986 in an optics experiment by Tomita and Chiao in which the rotation of the polarization plane of a wave propagating in a twisted optical fibre was interpreted as a Berry phase. In the same year it was found that the frequency splitting in the nuclear quadrupole resonance spectra of a slowly rotating nucleus could be ascribed to a Berry phase phenomenon.

The Berry phase is now known to play a significant role in many different areas of microscopic physics ranging from chemistry and molecular physics to optics, nuclear and solid state physics and relativistic quantum field theory. In all these areas the recognition of the non-integrable phase has led to a deepening of our understanding of the underlying quantum dynamics.