title: Quantum theory of light and noise polarization in nonlinear optics.
abstract: We present a consistent quantum theory of the electromagnetic field in nonlinearly responding causal media, with special emphasis on Chi(2) media. Starting from QED in linearly responding causal media, we develop a method to construct the cubic Hamiltonian expressed in terms of the complex nonlinear susceptibility in a quantum mechanically consistent way. In particular, we show that the method yields the nonlinear noise polarization, which together with the linear one is responsible for intrinsic quantum decoherence.
authors.affiliation: Quantum Optics and Laser Science, Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2BW, UK. s.scheel@imperial.ac.uk
authors.forename: Stefan
authors.initials: S
authors.lastname: Scheel
authors.forename: Dirk-Gunnar
authors.initials: DG
authors.lastname: Welsch