Unification of nonclassical signatures under the concept of quantum coherence

Abstract

Quantum coherence is the measurable consequence of the superposition principle, soit must be completely rooted in all the quantum effects. The feature common to all these behaviors of nature not affordable by classical theories is defined as nonclasicality. Being both rather elusive concepts, several interpretations of coherence and nonclassicality can be found. This makes their link sometimes trivial and sometimes contradictory. The main objective of this thesis is to find connections between the main signatures of nonclassical effects and coherence, analyzing if the latter can be considered the sole phenomenon underlying every quantum effect. During the process, we investigate the links between different potential causes of nonclassicality, such as complementarity, measurement process, and statistical separability, but also between different nonclassical effects, such as entanglement, nonclassical polarization, or sub-shot noise resolution. Since quantum coherence is a concept present in several contexts, we face it from different perspectives: as a resource, as an experimentally measurable magnitude and as a fundamental feature in metrology. We include in this picture the quantum nature of detectors as the unavoidable partner in every quantum observation...