Several quantities of interest in quantum information, including entanglement and purity, are nonlinear functions of the density matrix and cannot, even in principle, correspond to proper quantum o...

We present a universal technique for quantum-state estimation based on the maximum-likelihood method. This approach provides a positive-definite estimate for the density matrix from a sequence of… Expand

These notes originated out of a set of lectures in Quantum Optics and Quantum Information given by one of us (MGAP) at the University of Napoli and the University of Milano. A quite broad set of… Expand

This work extends the quantum discord to continuous variable systems and evaluates Gaussian quantum discord C(ϱ) for bipartite Gaussian states and explicitly maximize the extractable information over Gaussian measurements for squeezed-thermal states.Expand

We introduce a measure to quantify the non-Gaussian character of a quantum state: the quantum relative entropy between the state under examination and a reference Gaussian state. We analyze in detail… Expand

We address quantum critical systems as a resource in quantum estimation and derive the ultimate quantum limits to the precision of any estimator of the coupling parameters. In particular, if $L$… Expand

Entanglement does not correspond to an observable, and its evaluation always corresponds to an estimation procedure where the amount of entanglement is inferred from the measurements of one or more… Expand

The properties and the relationships of two recently proposed measures of non-Gaussianity (nG) of states and operations in continuous-variable systems and its use in quantum information are illustrated and a theorem connecting the QRE nG to the quantum Fisher information is presented.Expand