Quantum entropy function is a proposal for computing the entropy associated with the horizon of a black hole in the extremal limit, and is related via AdS/CFT correspondence to the dimension of the Hilbert space in a dual quantum mechanics. We show that in N = 4 supersymmetric string theories, quantum entropy function formalism naturally explains the origin of the subtle differences between the...

The quantum entropy at finite temperatures is analyzed by using models for colored quarks making up the physical states of the hadrons. We explicitly work out some special models for the structure of the states of SU(2) and SU(3) relating to the effects of the temperature on the quantum entropy. We show that the entropy of the singlet states monotonically decreases meaning that the mixing of th...

Quantum-mechanical entropies of position and momentum operators in a given state are shown to be reasonable and sensitive measures for squeezing of quantum fluctuations. It is shown to be true not only for states having Gaussian wave functions but also for more general, both pure and mixed, quantum states. A simple proof that the squeezing exhibited by the variance is always accompanied by a co...

Entropy is a central concept in both classical and quantum information theory, measuring the uncertainty and the information content in the state of a physical system. This paper reviews classical information theory and then proceeds to generalizations into quantum information theory. Both Shannon and Von Neumann entropy are discussed, making the connection to compressibility of a message strea...

The von Neumann entropy and the subentropy of a mixed quantum state are upper and lower bounds, respectively, on the accessible information of any ensemble consistent with the given mixed state. Here we define and investigate a set of quantities intermediate between entropy and subentropy. PACS numbers: 03.67.-a, 89.70.+c, 65.40.Gr 1 1 Entropy and subentropy The von Neumann entropy of a quantum...

We investigate a quantum dynamical entropy of one-dimesional quantum spin systems. We show that the dynamical entropy is bounded from above by a quantity which is related with group velocity determined by the interaction and mean entropy of the state. e-mail: [email protected]

In this work we prove that the possibility of superactivation of quantum channel capacities is determined by the mathematical properties of the quantum relative entropy function. Before our work this fundamental and purely mathematical connection between the quantum relative entropy function and the superactivation effect was completely unrevealed. We demonstrate the results for the quantum cap...

We show that a geometrical notion of entropy, definable in flat space, governs the first quantum correction to the Bekenstein-Hawking black hole entropy. We describe two methods for calculating this entropy – a straightforward Hamiltonian approach, and a less direct but more powerful Euclidean (heat kernel) method. The entropy diverges in quantum field theory in the absence of an ultraviolet cu...

There has been considerable interest in formulating measures of entanglement and applying them to extended quantum systems with many degrees of freedom, such as quantum spin chains, especially close to a quantum phase transition (see, e.g., several other reports in these proceedings). One of these measures is entanglement entropy. Suppose the whole system is in a pure quantum state |Ψ〉, with de...