Quantum Optics for Engineers

13

Introduction to Feynman Path Integrals

13.1  Introduction

The Feynman path integrals provide an alternative version of quantum mechanics (Feynman and Hibbs, 1965). This approach is outlined here since Feynman applied it to describe macroscopic beam divergence. The presentation is brief and limited since this subject was mainly selected as an example of an alternative version of quantum mechanics and is not utilized elsewhere in the book.

From a historical perspective, it should further be mentioned that the quantum analogue of the classical action was first introduced, as a concept, by Dirac in the early editions of his book The Principles of Quantum Mechanics where he introduced a section entitled “The Action Principle” (Dirac, 1978). ...