Polaritonic characteristics of insulator and superfluid phases in a coupled-cavity array

Recent studies of quantum phase transitions in coupled atom-cavity arrays have focused on the similarities between such systems and the Bose-Hubbard model. However, the bipartite nature of the atom-cavity systems that make up the array introduces some differences. In order to examine the unique features of the coupled-cavity system, the behavior of a simple two-site model is studied over a wide range of parameters. Four regions are identified, in which the ground state of the system may be classified as either a polaritonic insulator, a photonic superfluid, an atomic insulator, or a polaritonic superfluid.Comment: 7 pages, 9 figures, 1 table, REVTeX 4; published versio

Dynamics in a coupled-cavity array

The dynamics of a system composed of two coupled optical cavities, each containing a single two-level atom, is studied over a wide range of detuning and coupling values. A description of the field in terms of delocalized modes reveals that the detuning between the atoms and these modes is controlled by the coupling between the cavities; this detuning in turn governs the nature of the dynamics. If the atoms are highly detuned from both delocalized field modes, the dynamics becomes dispersive and an excitation may be transferred from the first atom to the second without populating the field. In the case of resonance between the atoms and one of the delocalized modes, state transfer between the atoms requires intermediate excitation of the field. Thus the interaction between the two atoms can be controlled by adjusting the coupling between the cavities.Comment: 11 pages, 3 figure

Cross-Kerr-based information transfer processes

The realization of nonclassical states is an important task for many applications of quantum information processing. Usually, properly tailored interactions, different from goal to goal, are considered in order to accomplish specific tasks within the general framework of quantum state engineering. In this paper we remark on the flexibility of a cross-Kerr nonlinear coupling in hybrid systems as an important ingredient in the engineering of nonclassical states. The general scenario we consider is the implementation of high cross-Kerr nonlinearity in cavity-quantum electrodynamics. In this context, we discuss the possibility of performing entanglement transfer and swapping between a qubit and a continuous-variable state. The recently introduced concept of entanglement reciprocation is also considered and shown to be possible with our scheme. We reinterpret some of our results in terms of applications of a generalized Ising interaction to systems of different nature.Comment: 8 pages, 4 figures, RevTeX

Concentration and purification of entanglement for qubit systems with ancillary cavity fields

We propose schemes for entanglement concentration and purification for qubit systems encoded in flying atomic pairs. We use a cavity-quantum electrodynamics setting as the paradigmatic scenario within which our proposals can be implemented. Maximally entangled pure states of qubits can be produced as a result of our protocols. In particular, the concentration protocol yields Bell states with the largest achievable theoretical probability while the purification scheme produces arbitrarily pure Bell states. The requirements for the implementation of these protocols are modest, within the state of the art, and we address all necessary steps in two specific set-ups based on experimentally mature microwave technology.Comment: 10 pages, 6 figure

Grazing and control of coral reef community structure by Diadema antillarum Philippi (Echinodermata: Echinoidea): A preliminary study

The grazing activities of the tropical echinoid Diadema antillarum Philippi can markedly influence the structure of the shallow-water epibenthic coral reef community. The elimination of an entire Diadema population from a patch reef in St. Croix, U.S. Virgin Islands resulted in a great increase in macro-algal biomass, alterations in species composition, shifts in dominance, an increase in species numbers, and a decrease in equitability...

Hearing the grass grow. Emotional and epistemological challenges of practice-near research

This paper discusses the concept of practice-near research in terms of the emotional and epistemological challenges that arise from the researcher coming 'near' enough to other people for psychological processes to ensue. These may give rise in the researcher to confusion, anxiety and doubt about who is who and what is what; but also to the possibility of real emotional and relational depth in the research process. Using illustrations from three social work doctoral research projects undertaken by students at the Tavistock Clinic and the University of East London the paper examines four themes that seem to the author to be central to meaningful practice-near research undertaken in a spirit of true emotional and epistemological open-mindedness: the smell of the real; losing our minds; the inevitability of personal change; and the discovery of complex particulars

Elastic cavitation, tube hollowing, and differential growth in plants and biological tissues

Elastic cavitation is a well-known physical process by which elastic materials under stress can open cavities. Usually, cavitation is induced by applied loads on the elastic body. However, growing materials may generate stresses in the absence of applied loads and could induce cavity opening. Here, we demonstrate the possibility of spontaneous growth-induced cavitation in elastic materials and consider the implications of this phenomenon to biological tissues and in particular to the problem of schizogenous aerenchyma formation

Seismic tomographic imaging of the Eastern Mediterranean Mantle: Implications for terminal-stage subduction, the uplift of Anatolia, and the development of the North Anatolian Fault

The Eastern Mediterranean captures the eastwest transition from active subduction of Earth'soldest oceanic lithosphere to continental collision, making it an ideal location to study terminalstagesubduction. Asthenospheric or subductionrelated processes are the main candidates for the region's ∼2kmuplift and Miocene volcanism; however, their relative importance is debated. To address these issues, wepresent new P and S wave relative arrivaltime tomographic models that reveal fast anomalies associatedwith an intact Aegean slab in the west, progressing to a fragmented, partially continental, Cyprean slabbelow central Anatolia. We resolve a gap between the Aegean and Cyprean slabs, and a horizontal tear in theCyprean slab below the Central Anatolian Volcanic Province. Below eastern Anatolia, the completelydetached “Bitlis” slab is characterized by fast wave speeds at ∼500 km depth. Assuming slab sinkingrates mirror ArabiaAnatolia convergence rates, the Bitlis slab's location indicates an Oligocene (∼26 Ma)breakoff. Results further reveal a strong velocity contrast across the North Anatolian Fault likelyrepresenting a 40–60 km decrease in lithospheric thickness from the Precambrian lithosphere north of thefault to a thinned Anatolian lithosphere in the south. Slow uppermostmantle wave speeds below activevolcanoes in eastern Anatolia, and ratios of P to S wave relative traveltimes, indicate a thin lithosphere andmelt contributions. Positive central and eastern Anatolian residual topography requires additional supportfrom hot/buoyant asthenosphere to maintain the 1–2 km elevation in addition to an almost absentlithospheric mantle. Smallscale fast velocity structures in the shallow mantle above the Bitlis slab maytherefore be drips of Anatolian lithospheric mantle