Modelling the Recoherence of Mesoscopic Superpositions in Dissipative Environments

A model is presented to describe the recently proposed experiment (J. Raimond, M. Brune and S. Haroche Phys. Rev. Lett {\bf 79}, 1964 (1997)) where a mesoscopic superposition of radiation states is prepared in a high-Q cavity which is coupled to a similar resonator. The dynamical coherence loss of such state in the absence of dissipation is reversible and can in principle be observed. We show how this picture is modified due to the presence of the environmental couplings. Analytical expressions for the experimental conditional probabilities and the linear entropy are given. We conclude that the phenomenon can still be observed provided the ratio between the damping constant and the inter-cavities coupling does not exceed about a few percent. This observation is favored for superpositions of states with large overlap.Comment: 13 pages, 6 figure

Time evolution of the classical and quantum mechanical versions of diffusive anharmonic oscillator: an example of Lie algebraic techniques

We present the general solutions for the classical and quantum dynamics of the anharmonic oscillator coupled to a purely diffusive environment. In both cases, these solutions are obtained by the application of the Baker-Campbell-Hausdorff (BCH) formulas to expand the evolution operator in an ordered product of exponentials. Moreover, we obtain an expression for the Wigner function in the quantum version of the problem. We observe that the role played by diffusion is to reduce or to attenuate the the characteristic quantum effects yielded by the nonlinearity, as the appearance of coherent superpositions of quantum states (Schr\"{o}dinger cat states) and revivals.Comment: 21 pages, 6 figures, 2 table

Continuous Monitoring of Dynamical Systems and Master Equations

We illustrate the equivalence between the non-unitary evolution of an open quantum system governed by a Markovian master equation and a process of continuous measurements involving this system. We investigate a system of two coupled modes, only one of them interacting with external degrees of freedom, represented, in the first case, by a finite number of harmonic oscillators, and, in the second, by a sequence of atoms where each one interacts with a single mode during a limited time. Two distinct regimes appear, one of them corresponding to a Zeno-like behavior in the limit of large dissipation

Quantifying the decay of quantum properties in single-mode states

The dissipative dynamics of Gaussian squeezed states (GSS) and coherent superposition states (CSS) are analytically obtained and compared. Time scales for sustaining different quantum properties such as squeezing, negativity of the Wigner function or photon number distribution are calculated. Some of these characteristic times also depend on initial conditions. For example, in the particular case of squeezing, we find that while the squeezing of CSS is only visible for small enough values of the field intensity, in GSS it is independent of this quantity, which may be experimentally advantageous. The asymptotic dynamics however is quite similar as revealed by the time evolution of the fidelity between states of the two classes.Comment: Accepted versio

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time, and attempts to address it require a clear understanding of how ecological communities respond to environmental change across time and space. While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes, vast areas of the tropics remain understudied. In the American tropics, Amazonia stands out as the world's most diverse rainforest and the primary source of Neotropical biodiversity, but it remains among the least known forests in America and is often underrepresented in biodiversity databases. To worsen this situation, human-induced modifications may eliminate pieces of the Amazon's biodiversity puzzle before we can use them to understand how ecological communities are responding. To increase generalization and applicability of biodiversity knowledge, it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple organism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region's vulnerability to environmental change. 15%–18% of the most neglected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lost

Óptica de nanopartículas y nanocompuestos

IP 1101-05-036-99of the XV latinamerican symposium on solid state physics (SlafesXV), Cartagena de Indias, Colombia, November;1 to 5, 1999 / latinamerican simposium on solid state physics(slafes XV)(15: 1999 nov. 1-5 : Cartagena de;Indias, Colombia) Guest editors J. Giraldo, L. Quiroga, R.Merlin, J.R. Leite. -- En: Physica status solidi;(b) : Basic research Vol. 220, no. 1 (july 2000): p. 1-804. --ISSN 03701972.;Oaxaca: Sociedad Mexicana de ciencia de superficies y vacio A.C., 2000. --28 cm. -- REVISTA(S): Proceedings;ARTICULOS EN REVISTA: Funcion dielectrica de un medio quepercola / Adriana Gutierrez Rodriguez, Jairo;Giraldo Gallo. -- En: Revista colombiana de un medio que percola. -- Vol.32, no. 1 (2000). -- A statistical;model for flash thermal desorption of carbon dioxide frompolycrystallinemolybdenum / L.D Lopez Carreño, A.J.;Ramirez Cuesta, L.Viscido, J.M Heras. -- En: Journal of molecular catalysis a: chemical. -- Vol. 167 (june;2001); p. 157-163. -- Diffusive like minibands in finite superlattices ofdisordered quantum wells / R.R. Rey;Gonzalez, E. Machado -- En: Brazilian journal of physics.'-- Vol. 31 no. 4(dic. 2001). -- RF sputtered a Si:H;and aGe:H films: a comparative study / A.R. Zanatta, F. Fajardo,M. Mulato, M.M. Lima, F.C. Marques, I.;Chambouleyron. -- En: Asian journal of physics. -- Vol. 9(2000); p. 681.'-- PONENCIA(S) en Congreso: Atomic;ordering in Cd1-xZnxTe for low Zn concentration: optical,thermal and structural characterization / A.;Guterrez, M.E. Rodriguez, O. Zelaya, C. Vasquez, L. Baños,JairoGiraldo Gallo. -- En: Sociedad mexicana de;ciencia de superficies y vacio A.C. 20 congreso nacional.(20:2000 ago.28 - sep.1 :Oxaca, Mexico). -