Dynamics of the entanglement between two oscillators in the same environment

We provide a complete characterization of the evolution of entanglement between two oscillators coupled to a common environment. For initial Gaussian states we identify three phases with different qualitative long time behavior: There is a phase where entanglement undergoes a sudden death (SD). Another phase (SDR) is characterized by an infinite sequence of events of sudden death and revival of entanglement. In the third phase (NSD) there is no sudden death of entanglement, which persist for long time. The phase diagram is described and analytic expressions for the boundary between phases are obtained. Numerical simulations show the accuracy of the analytic expressions. These results are applicable to a large variety of non--Markovian environments. The case of non--resonant oscillators is also numerically investigated.Comment: 4 pages, 5 figure

Entanglement dynamics during decoherence

The evolution of the entanglement between oscillators that interact with the same environment displays highly non-trivial behavior in the long time regime. When the oscillators only interact through the environment, three dynamical phases were identified and a simple phase diagram characterizing them was presented. Here we generalize those results to the cases where the oscillators are directly coupled and we show how a degree of mixidness can affect the final entanglement. In both cases, entanglement dynamics is fully characterized by three phases (SD: sudden death, NSD: no-sudden death and SDR: sudden death and revivals) which cover a phase diagram that is a simple variant of the previously introduced one. We present results when the oscillators are coupled to the environment through their position and also for the case where the coupling is symmetric in position and momentum (as obtained in the RWA). As a bonus, in the last case we present a very simple derivation of an exact master equation valid for arbitrary temperatures of the environment.Comment: to appear in QIP special issue on Quantum Decoherence and Entanglemen

Dynamical phases for the evolution of the entanglement between two oscillators coupled to the same environment

We study the dynamics of the entanglement between two oscillators that are initially prepared in a general two-mode Gaussian state and evolve while coupled to the same environment. In a previous paper we showed that there are three qualitatively different dynamical phases for the entanglement in the long time limit: sudden death, sudden death and revival and no-sudden death [Paz & Roncaglia, Phys. Rev. Lett. 100, 220401 (2008)]. Here we generalize and extend those results along several directions: We analyze the fate of entanglement for an environment with a general spectral density providing a complete characterization of the corresponding phase diagrams for ohmic and sub--ohmic environments (we also analyze the super-ohmic case showing that for such environment the expected behavior is rather different). We also generalize previous studies by considering two different models for the interaction between the system and the environment (first we analyze the case when the coupling is through position and then we examine the case where the coupling is symmetric in position and momentum). Finally, we analyze (both numerically and analytically) the case of non-resonant oscillators. In that case we show that the final entanglement is independent of the initial state and may be non-zero at very low temperatures. We provide a natural interpretation of our results in terms of a simple quantum optics model.Comment: 18 pages, 13 figure

On the publication and pagination of Ameghino's (1894) taxonomy of Santacrucian mammals

DURING the course of our research on the paleobiology and systematics ofmammalian remains of the Santa Cruz Formation of Argentine Patagonia,we becameaware of differences in the early literature dealing with Santacrucian (late Early Miocene) mammals. Although literature errors are not uncommon, they are often only an inconvenience. However, in this case it involves an article in which numerous taxa were erected, so that particular attention must be paid to the circumstances of its publication. The article in question is Florentino Ameghino?s (1894a, b) Énumération synoptique des espèces de mammifères fossiles des formations éocènes de Patagonie. This article was published formally in 1893 in the Boletín de la Academia Nacional de Ciencias en Córdoba and also in 1894, with identical title and text but different pagination, as an offprint.Fil: De Iuliis, Gerardo. University of Toronto; Canadá. Royal Ontario Museum; CanadáFil: Fernicola, Juan Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; ArgentinaFil: Racco, Augusto. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; Argentin

Work measurement as a generalized quantum measurement

We present a new method to measure the work $w$ performed on a driven quantum system and to sample its probability distribution $P(w)$. The method is based on a simple fact that remained unnoticed until now: Work on a quantum system can be measured by performing a generalized quantum measurement at a single time. Such measurement, which technically speaking is denoted as a POVM (positive operator valued measure) reduces to an ordinary projective measurement on an enlarged system. This observation not only demystifies work measurement but also suggests a new quantum algorithm to efficiently sample the distribution $P(w)$. This can be used, in combination with fluctuation theorems, to estimate free energies of quantum states on a quantum computer.Comment: 4 page