Entanglement in thermal equilibrium states

We revisist the issue of entanglement of thermal equilibrium states in composite quantum systems. The possible scenarios are exemplified in bipartite qubit/qubit and qubit/qutrit systems.Comment: 4 figure

Two-spin subsystem entanglement in spin 1/2 rings with long range interactions

We consider the two-spin subsystem entanglement for eigenstates of the Hamiltonian $$H= \sum_{1\leq j< k \leq N} (\frac{1}{r_{j,k}})^{\alpha} {\mathbf \sigma}_j\cdot {\mathbf \sigma}_k$$ for a ring of $N$ spins 1/2 with asssociated spin vector operator $(\hbar /2){\bf \sigma}_j$ for the $j$-th spin. Here $r_{j,k}$ is the chord-distance betwen sites $j$ and $k$. The case $\alpha =2$ corresponds to the solvable Haldane-Shastry model whose spectrum has very high degeneracies not present for $\alpha \neq 2$. Two spin subsystem entanglement shows high sensistivity and distinguishes $\alpha =2$ from $\alpha \neq 2$. There is no entanglement beyond nearest neighbors for all eigenstates when $\alpha =2$. Whereas for $\alpha \neq 2$ one has selective entanglement at any distance for eigenstates of sufficiently high energy in a certain interval of $\alpha$ which depends on the energy. The ground state (which is a singlet only for even $N$) does not have entanglement beyond nearest neighbors, and the nearest neighbor entanglement is virtually independent of the range of the interaction controlled by $\alpha$.Comment: 16 figure

Zeno Dynamics in Quantum Statistical Mechanics

We study the quantum Zeno effect in quantum statistical mechanics within the operator algebraic framework. We formulate a condition for the appearance of the effect in W*-dynamical systems, in terms of the short-time behaviour of the dynamics. Examples of quantum spin systems show that this condition can be effectively applied to quantum statistical mechanical models. Further, we derive an explicit form of the Zeno generator, and use it to construct Gibbs equilibrium states for the Zeno dynamics. As a concrete example, we consider the X-Y model, for which we show that a frequent measurement at a microscopic level, e.g. a single lattice site, can produce a macroscopic effect in changing the global equilibrium.Comment: 15 pages, AMSLaTeX; typos corrected, references updated and added, acknowledgements added, style polished; revised version contains corrections from published corrigend

Free energy density for mean field perturbation of states of a one-dimensional spin chain

Motivated by recent developments on large deviations in states of the spin chain, we reconsider the work of Petz, Raggio and Verbeure in 1989 on the variational expression of free energy density in the presence of a mean field type perturbation. We extend their results from the product state case to the Gibbs state case in the setting of translation-invariant interactions of finite range. In the special case of a locally faithful quantum Markov state, we clarify the relation between two different kinds of free energy densities (or pressure functions).Comment: 29 pages, Section 5 added, to appear in Rev. Math. Phy

Aspectos sobre operación y normativas de inversores fotovoltaicos para inyección a red de baja tensión

Se presenta en este trabajo un análisis sobre el funcionamiento y algunas consideraciones de operación de un inversor fotovoltaico para inyección de energía a la red de baja tensión. Más precisamente se estudian los inversores monofásicos sin transformador de aislamiento a la salida, los más utilizados en instalaciones de hasta 5kW. Así mismo se muestra un resumen de las diferentes normativas internacionales que deben satisfacer en torno a seguridad eléctrica, y conexión a red.An analysis on the functioning and considerations of operation of a photovoltaic inverter for power feed into the low voltage network is presented in this paper. More precisely the single-phase inverters without isolation transformer at the output, the most widely used systems up to 5 kW are studied. Also a summary of different international regulations to be met regarding electrical safety and grid code is shown.Tema 13: Generación distribuida.Facultad de Arquitectura y Urbanism

Aspectos sobre operación y normativas de inversores fotovoltaicos para inyección a red de baja tensión

Se presenta en este trabajo un análisis sobre el funcionamiento y algunas consideraciones de operación de un inversor fotovoltaico para inyección de energía a la red de baja tensión. Más precisamente se estudian los inversores monofásicos sin transformador de aislamiento a la salida, los más utilizados en instalaciones de hasta 5kW. Así mismo se muestra un resumen de las diferentes normativas internacionales que deben satisfacer en torno a seguridad eléctrica, y conexión a red.An analysis on the functioning and considerations of operation of a photovoltaic inverter for power feed into the low voltage network is presented in this paper. More precisely the single-phase inverters without isolation transformer at the output, the most widely used systems up to 5 kW are studied. Also a summary of different international regulations to be met regarding electrical safety and grid code is shown.Tema 13: Generación distribuida.Facultad de Arquitectura y Urbanism

Aspectos sobre operación y normativas de inversores fotovoltaicos para inyección a red de baja tensión

Se presenta en este trabajo un análisis sobre el funcionamiento y algunas consideraciones de operación de un inversor fotovoltaico para inyección de energía a la red de baja tensión. Más precisamente se estudian los inversores monofásicos sin transformador de aislamiento a la salida, los más utilizados en instalaciones de hasta 5kW. Así mismo se muestra un resumen de las diferentes normativas internacionales que deben satisfacer en torno a seguridad eléctrica, y conexión a red.An analysis on the functioning and considerations of operation of a photovoltaic inverter for power feed into the low voltage network is presented in this paper. More precisely the single-phase inverters without isolation transformer at the output, the most widely used systems up to 5 kW are studied. Also a summary of different international regulations to be met regarding electrical safety and grid code is shown.Tema 13: Generación distribuida.Facultad de Arquitectura y Urbanism

Kakutani Dichotomy on Free States

Two quasi-free states on a CAR or CCR algebra are shown to generate quasi-equivalent representations unless they are disjoint.Comment: 12 page

Proyecto IRESUD: interconexión de sistemas fotovoltaicos a la red eléctrica en ambientes urbanos. estado de avance a julio de 2014 y primeras mediciones en sistemas piloto

En el marco de una convocatoria del Ministerio de Ciencia, Tecnología e Innovación Productiva, se conformó, en el año 2011, el consorcio público-privado IRESUD entre la Comisión Nacional de Energía Atómica (CNEA), la Universidad Nacional de San Martín (UNSAM) y 5 empresas privadas, para la ejecución del proyecto “Interconexión de Sistemas Fotovoltaicos a la Red Eléctrica en Ambientes Urbanos”. El principal objetivo del mismo es introducir en el país tecnologías asociadas con la interconexión a la red eléctrica, en áreas urbanas, de sistemas fotovoltaicos (FV), contemplando para ello cuestiones técnicas, económicas y regulatorias. En este trabajo, se presenta el grado de avance del proyecto en lo referente a las cuestiones regulatorias y a las instalaciones piloto realizadas o en ejecución en diferentes partes del país. Asimismo, se muestran las primeras mediciones de algunas de las instalaciones actualmente en operación y se analiza el comportamiento de un inversor FV de conexión a red.Fil: Durán, J. C.. Comisión Nacional de Energía Atómica; Argentina. Universidad Nacional de San Martín; ArgentinaFil: Socolovsky, Hernan Pablo. Comisión Nacional de Energía Atómica; Argentina. Universidad Nacional de San Martín; ArgentinaFil: Raggio, D.. Comisión Nacional de Energía Atómica; ArgentinaFil: Godfrin, Elena María. Comisión Nacional de Energía Atómica; ArgentinaFil: Jakimczyk, J.. Universidad Tecnológica Nacional; ArgentinaFil: Martinez Bogado, Mónica Gladys. Universidad Nacional de San Martín; Argentina. Comisión Nacional de Energía Atómica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Diaz, F. J.. Universidad Nacional de La Plata. Facultad de Informática; ArgentinaFil: Castro, N. E.. Universidad Nacional de La Plata. Facultad de Informática; ArgentinaFil: Pedro, G.. Provincia del Neuquen. Ministerio de Hacienda Obras y Servivcios Publicos. Ente Provincial de Energia del Neuquen; ArgentinaFil: Sepúlveda, O.. Provincia del Neuquen. Ministerio de Hacienda Obras y Servivcios Publicos. Ente Provincial de Energia del Neuquen; ArgentinaFil: Argañaraz, C.. Provincia del Neuquen. Ministerio de Hacienda Obras y Servivcios Publicos. Ente Provincial de Energia del Neuquen; ArgentinaFil: Benítez, E.. Universidad Nacional de Luján; ArgentinaFil: Roldán, A.. Universidad Nacional de Luján; ArgentinaFil: Righini, R.. Universidad Nacional de Luján; Argentin

Faithful Squashed Entanglement

Squashed entanglement is a measure for the entanglement of bipartite quantum states. In this paper we present a lower bound for squashed entanglement in terms of a distance to the set of separable states. This implies that squashed entanglement is faithful, that is, strictly positive if and only if the state is entangled. We derive the bound on squashed entanglement from a bound on quantum conditional mutual information, which is used to define squashed entanglement and corresponds to the amount by which strong subadditivity of von Neumann entropy fails to be saturated. Our result therefore sheds light on the structure of states that almost satisfy strong subadditivity with equality. The proof is based on two recent results from quantum information theory: the operational interpretation of the quantum mutual information as the optimal rate for state redistribution and the interpretation of the regularised relative entropy of entanglement as an error exponent in hypothesis testing. The distance to the set of separable states is measured by the one-way LOCC norm, an operationally-motivated norm giving the optimal probability of distinguishing two bipartite quantum states, each shared by two parties, using any protocol formed by local quantum operations and one-directional classical communication between the parties. A similar result for the Frobenius or Euclidean norm follows immediately. The result has two applications in complexity theory. The first is a quasipolynomial-time algorithm solving the weak membership problem for the set of separable states in one-way LOCC or Euclidean norm. The second concerns quantum Merlin-Arthur games. Here we show that multiple provers are not more powerful than a single prover when the verifier is restricted to one-way LOCC operations thereby providing a new characterisation of the complexity class QMA.Comment: 24 pages, 1 figure, 1 table. Due to an error in the published version, claims have been weakened from the LOCC norm to the one-way LOCC nor