Atom Interferometry and the Quantum Theory of Measurement

Abstract

This chapter discusses atom interferometry and the quantum theory of measurement. The interferometry that is supremely elegant and profoundly practical part of conventional optics is deeply enriched by the advent of neutron and atom interferometry for several reasons. The shorter de Broglie wavelength of massive particles makes possible new devices such as the matter–wave gyroscope, whose sensitivities, in principle, far exceed those of their electromagnetic predecessors, such as the laser gyroscope. The first half of the chapter discusses the role of complementarity and Welcher Weg information in the context of two modern versions of the Young's double-slit experiment. The second half of the chapter addresses the more practical aspect of how a macroscopic device with many degrees of freedom affects the measurement of a microscopic object. The macroscopic device is a Stern–Gerlach interferometer in which two partial beams of spln-1/2 atoms are macroscopically separated and then reunited.