Sensing and decision-making in random search

While microscopic organisms can use gradient-based search to locate resources, this strategy can be poorly suited to the sensory signals available to macroscopic organisms. We propose a framework that models search-decision making in cases where sensory signals are infrequent, subject to large fluctuations, and contain little directional information. Our approach simultaneously models an organism's intrinsic movement behavior (e.g. Levy walk) while allowing this behavior to be adjusted based on sensory data. We find that including even a simple model for signal response can dominate other features of random search and greatly improve search performance. In particular, we show that a lack of signal is not a lack of information. Searchers that receive no signal can quickly abandon target-poor regions. Such phenomena naturally give rise to the area-restricted search behavior exhibited by many searching organisms

DC-assisted microwave quenching of YBa2Cu3O7-{\delta} coplanar waveguide to a highly dissipative state

The paper reports on finding the effect of a strong change in the microwave losses in an HTS-based coplanar waveguide (CPW) at certain values of the input power Pin and direct current Idc. CPW on the basis of 150 nm thick YBa2Cu3O7-{\delta} epitaxial film on a single crystal MgO substrate was studied experimentally. A sharp and reversible transition of the CPW into a strongly dissipative state at the certain meanings of Pin and Idc depending on temperature was observed. Apparently the effect can be explained by self-heating of HTS structure caused by magnetic flux flow under the joint influence of MW and DC.Comment: 9 pages, 5 figures, 17 reference

Irreversibility line and low-field grain-boundary pinning in electron-doped superconducting thin films

AC magnetic susceptibilities of electron-doped Pr_{1.85}Ce_{0.15}CuO_4 (PCCO) and Sm_{1.85}Ce_{0.15}CuO_4 (SCCO) granular thin films have been measured as a function of temperature and magnetic-field strength. Depending on the level of homogeneity of our films, two different types of the irreversibility line (IL) defined as the intergrain-loss peak temperature in the imaginary part of susceptibility have been found. The obtained results are described via the critical-state model taking into account the low-field grain-boundary pinning. The extracted pinning-force densities in more granular SCCO films turn out to be four times larger than their counterparts in less granular PCCO films

YBCO microwave resonators for strong collective coupling with spin ensembles

Coplanar microwave resonators made of 330 nm-thick superconducting YBCO have been realized and characterized in a wide temperature ($T$, 2-100 K) and magnetic field ($B$, 0-7 T) range. The quality factor $Q_L$ exceeds 10$^4$ below 55 K and it slightly decreases for increasing fields, remaining 90$\%$ of $Q_L(B=0)$ for $B=7$ T and $T=2$ K. These features allow the coherent coupling of resonant photons with a spin ensemble at finite temperature and magnetic field. To demonstrate this, collective strong coupling was achieved by using DPPH organic radical placed at the magnetic antinode of the fundamental mode: the in-plane magnetic field is used to tune the spin frequency gap splitting across the single-mode cavity resonance at 7.75 GHz, where clear anticrossings are observed with a splitting as large as $\sim 82$ MHz at $T=2$ K. The spin-cavity collective coupling rate is shown to scale as the square root of the number of active spins in the ensemble.Comment: to appear in Appl. Phys. Let

The electromagnetic component of albedo from superhigh energy cascades in dense media

Albedo from cascades induced in iron by high energy gamma quanta were Monte Carlo simulated. Thereafter the albedo electromagnetic component from proton induced cascades were calculated analytically. The calculations showed that the albedo electromagnetic component increases more rapidly than the nuclear active component and will dominate at sufficiently high energies

Completeness of the classical 2D Ising model and universal quantum computation

We prove that the 2D Ising model is complete in the sense that the partition function of any classical q-state spin model (on an arbitrary graph) can be expressed as a special instance of the partition function of a 2D Ising model with complex inhomogeneous couplings and external fields. In the case where the original model is an Ising or Potts-type model, we find that the corresponding 2D square lattice requires only polynomially more spins w.r.t the original one, and we give a constructive method to map such models to the 2D Ising model. For more general models the overhead in system size may be exponential. The results are established by connecting classical spin models with measurement-based quantum computation and invoking the universality of the 2D cluster states.Comment: 4 pages, 1 figure. Minor change

Superconducting Microwave Cavity Made of Bulk MgB2

We report the successful manufacture and characterization of a microwave resonant cylindrical cavity made of bulk MgB2 superconductor (Tc = 38.5 K), which has been produced by the Reactive Liquid Mg Infiltration technique. The quality factor of the cavity for the TE011 mode, resonating at 9.79 GHz, has been measured as a function of the temperature. At T = 4.2 K, the unloaded quality factor is 2.2x10^5; it remains of the order of 10^5 up to T ~ 30 K. We discuss the potential performance improvements of microwave cavities built from bulk MgB2 materials produced by reactive liquid Mg infiltration.Comment: 7 pages, 2 embedded figures, accepted for publication in Supercond. Sci. Techno

Graph Concatenation for Quantum Codes

Graphs are closely related to quantum error-correcting codes: every stabilizer code is locally equivalent to a graph code, and every codeword stabilized code can be described by a graph and a classical code. For the construction of good quantum codes of relatively large block length, concatenated quantum codes and their generalizations play an important role. We develop a systematic method for constructing concatenated quantum codes based on "graph concatenation", where graphs representing the inner and outer codes are concatenated via a simple graph operation called "generalized local complementation." Our method applies to both binary and non-binary concatenated quantum codes as well as their generalizations.Comment: 26 pages, 12 figures. Figures of concatenated [[5,1,3]] and [[7,1,3]] are added. Submitted to JM

Emergence of the Shackleton Range from beneath the Antarctic Ice Sheet due to glacial erosion

This paper explores the long-term evolution of a subglacial fjord landscape in the Shackleton Range, Antarctica. We propose that prolonged ice-sheet erosion across a passive continental margin caused troughs to deepen and lower the surrounding ice-sheet surface, leaving adjacent mountains exposed. Geomorphological evidence suggests a change in the direction of regional ice flow accompanied emergence. Simple calculations suggest that isostatic compensation caused by the deepening of bounding ice-stream troughs lowered the ice-sheet surface relative to the mountains by ~800m. Use of multiple cosmogenic isotopes on bedrock and erratics (26Al, 10Be, 21Ne) provides evidence that overriding of the massif and the deepening of the adjacent troughs occurred earlier than the Quaternary. Perhaps this occurred in the mid-Miocene, as elsewhere in East Antarctica in the McMurdo Dry Valleys and the Lambert basin. The implication is that glacial erosion instigates feedback that can change ice-sheet thickness, extent, and direction of flow. Indeed, as the subglacial troughs evolve over millions of years, they increase topographic relief; and this changes the dynamics of the ice sheet. © 2013 Elsevier B.V