Spatial entanglement in optical parametric down-conversion

This chapter and Chapter 5 constitute a direct continuation of Chapter 1, with a description of the developments in the continuous variable approach to quantum imaging, achieved in the framework of QUANTIM. Whereas Chapter 2 treats the traveling-wave configuration for PDC, the discussion of Chapter 5 focuses on the cavity configuration of optical parametric oscillators. The structure of this chapter is as follows. Section 2.2 presents the theoretical picture of spatial entanglement in type-II materials. Contrary to most literature on PDC, the emphasis is on the high-gain regime. Section 2.3 describes the experimental observations of those theoretical predictions outlined in Section 2.2, which concern the quantum correlations in the far field, with an associated phenomenon of photon antibunching in space. In the final Section 2.4 we illustrate the multiphoton, multimode polarization entanglement in the high-gain PDC. Instead of considering the standard polarization entanglement in single pairs of signal-idler photons, we focus on collective polarization entanglement properties at the macroscopic level. © 2007 Springer.