Chapter 5 Quantum imaging

Publisher Summary With respect to the classical area of imaging, the field of quantum imaging (QI) aims to devise novel techniques for optical imaging and parallel information processing at the quantum level, by exploiting the quantum nature of light and the intrinsic parallelism of optical signals. As a matter of fact, the cross-section of a broad-area radiation beam offers the possibility for multichannel configurations. For example, in each of these independent regions the light may be squeezed, or there may be quantum entanglement between pair of channels. Essentially this approach paves the way to parallel quantum information processing, basically different from the sequential configuration that characterizes, for instance, most schemes of quantum cryptography, in which one detects one photon (or one photon pair) at a time. Such a parallel configuration allows a remarkable increase of the information capacity of the system. This chapter discusses the spatial aspects of squeezing (in particular local squeezing) and of quantum images, with related aspects such as the interference of signal and idler waves. Quantum spatial correlations in spontaneous parametric down-conversion (PDC), ghost imaging, image amplification by PDC, and the detection of small displacements with a precision beyond the standard limit (quantum laser pointer) are discussed.