Non-classicality: Quantum entanglement and beyond. Novel concepts and applications

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Quantum Mechanics predicts physical effects that cannot be understood from the point of view of Classical Mechanics. From a fundamental point of view, we are interested in this "quantumness" of physical systems in order to test and better understand Quantum Mechanics itself. From a practical point of view, any quantum effect may form the basis for truly disruptive technologies. In particular, the development of the field of Quantum Information Processing is the result of the recognition that "Information is physical" (R. Landauer), combined with the fact that the basic laws of nature are quantum. Applications of Quantum Information Processing range from a possible exponential speed-up of quantum computers over classical computers---e.g., in solving computational problems and efficiently simulating quantum systems---to secure cryptographic communication schemes. Taking advantage of quantum behavior requires the best possible understanding of it. The project aims at characterizing and exploiting the quantum properties and behaviour of single and multipartite systems. Quantum entanglement---i.e., stronger-than-classical correlations between two (or more) quantum systems---has been proved to be a key resource in many Quantum Information Processing tasks and is considered the most prominent quantum feature. On the other hand, non-classical properties of correlations other than entanglement have been generally overlooked until recently, but could lead to more practical ways to harness the "quantum power". The project will address the questions: "how do correlations in the quantum world differ from correlations in the classical world?"; "how can we quantify, manipulate and take advantage of quantumness?"; "is entanglement always a useful resource?"; "are there simple tests to check that experimental devices work in a quantum regime?"; "what makes quantum computers potentially more powerful than classical computers?". In providing an answer to these questions we will adopt the unifying point of view that non-classicality is a very general feature of quantum systems, which goes well beyond entanglement. The latter will be studied as an extreme form of non-classicality that allows otherwise impossible effects.