A constructive index theorem, phase operators, and phase-difference operators

Abstract

A constructive reversed index theorem concerning the polar decomposition of an operator into a product of a unitary exponential phase operator and a Hermitian amplitude operator is investigated. Its applications to the construction of Hermitian phase operators of fermions and phase-difference operators between bosons or fermions are presented. Specifically, a Hermitian operator is constructed for the phase difference between a single-mode fermion and boson, which is justified by the fact that it is exactly the interaction part of the Hamiltonian of the Jaynes-Cummings Model. Furthermore, a Hermitian phase operator of a single-mode boson can also be defined referring to a single-mode fermion. All those quantized phases and phase-differences are found to obey a quantum addition rule instead of the ordinary commutative addition rule.