Quantum Hopfield neural network

Quantum computing allows for the potential of significant advancements in both the speed and the capacity of widely used machine learning techniques. Here we employ quantum algorithms for the Hopfield network, which can be used for pattern recognition, reconstruction, and optimization as a realization of a content-addressable memory system. We show that an exponentially large network can be stored in a polynomial number of quantum bits by encoding the network into the amplitudes of quantum states. By introducing a classical technique for operating the Hopfield network, we can leverage quantum algorithms to obtain a quantum computational complexity that is logarithmic in the dimension of the data. We also present an application of our method as a genetic sequence recognizer.Comment: 13 pages, 3 figures, final versio

Concepts in ichnotaxonomy illustrated by small round holes in shells

La clasificación de las pistas fósiles requiere un doble sistema de nomenclatura. El nombre de la pista fósil (ichnotaxon) está basado en la morfologia de la estructura, mientras que el taxon biológico  representa la posicion filogenética que se interpreta del organismo causante. Los dos sistemas de nomenclatura no se pueden intercambiar, y ambos son necesarios para la completa clasificacion dela pista. A muchas de estas pistas no les ha sido aún atribuido unichnotaxon descriptivo, pero ya que las  pistas fósiles re quieren nombres si han de ser tratadas sistemáticamente, se ofrece comunmente en tales  casos un biotaxon interpretativo en lugar del ichnotaxon que no se ha descritotodavia Este procedimiento tiende a desviar la atención de la verdadera naturaleza de la pista fósil e implica una falsa  exactitud en la determinación filogenética, lo cual conduce a conclusiones paleobiologicas poco seguras. Estos puntos quedan bien ilustrados por el ejemplo de unas perforaciones pequeíias y redondas sobre  conchas. Son pistas fósiles abundantes y, no teniendo ichnotaxon, tienden a ser relacionadas con la  accion perforante de los gasteropedos-naticidos y muricidos-sobre conchas. Sin embargo, varios grupos  más de gasteropodos producen perforaciones redondas, al igual que los cefalopodos octopodos,  turbelarios, nemátodos y braquiópodos articulados, pero su acción es poco conocida. Antes de embarcarse en tales especulaciones, como son los organismos causantes, es necesario un ichnotaxón para atraer la atención hacia estas pistas fosiles y aumentarel rigorde su tratamiento. Sólo cuando sumorfologia y distribución sean mejor conocidas estaremos en una posición mejor para discutir sus  atribuciones filogenéticas

Unifying approach to the quantification of bipartite correlations by Bures distance

The notion of distance defined on the set of states of a composite quantum system can be used to quantify total, quantum and classical correlations in a unifying way. We provide new closed formulae for classical and total correlations of two-qubit Bell-diagonal states by considering the Bures distance. Complementing the known corresponding expressions for entanglement and more general quantum correlations, we thus complete the quantitative hierarchy of Bures correlations for Bell-diagonal states. We then explicitly calculate Bures correlations for two relevant families of states: Werner states and rank-2 Bell-diagonal states, highlighting the subadditivity which holds for total correlations with respect to the sum of classical and quantum ones when using Bures distance. Finally, we analyse a dynamical model of two independent qubits locally exposed to non-dissipative decoherence channels, where both quantum and classical correlations measured by Bures distance exhibit freezing phenomena, in analogy with other known quantifiers of correlations.Comment: 18 pages, 4 figures; published versio

Remotely Sensed Estimates of Evapotranspiration in Agricultural Areas of Northwestern Nevada: Drought, Reliance, and Water Transfers

The arid landscape of northwestern Nevada is punctuated by agricultural communities that rely on water primarily supplied by the diversion of surface waters and secondarily by groundwater resources. Annual precipitation in the form of winter snowfall largely determines the amount of surface water that is available for irrigation for the following agricultural growing season. During years of insufficient surface water supplies, particular basins can use groundwater in order to meet irrigation needs. The amount of water used to irrigate agricultural land is influenced by land use changes, such as fallowing, and water right transfers from irrigation to municipal use. To evaluate agricultural water consumption with respect to variations in weather, water supply, and land use changes, monthly estimates of evapotranspiration (ET) were derived from Landsat multispectral optical and thermal imagery over a eleven-year period (2001 to 2011) and compared to variations in weather, water supply, and land use across four hydrographic areas in northwestern Nevada. Monthly ET was estimated using a land surface energy balance model, Mapping EvapoTranspiration at high Resolution with Internalized Calibration (METRIC), using Landsat 5 and Landsat 7 imagery combined with local atmospheric water demand estimates. Estimates of net ET were created by subtracting monthly precipitation from METRIC-derived ET, and seasonal estimates were generated by combining monthly ET for April-October (the regional agricultural growing season). Results highlight that a range of geographic, climatic, hydrographic, and anthropogenic factors influence ET. Hydrographic areas such as Mason Valley have the ability to mitigate deficiencies in surface water supplies by pumping supplemental groundwater, thereby resulting in low annual variability in ET. Conversely, the community of Lovelock has access to limited upstream surface water storage and is restricted by groundwater that is saline and unsuitable for irrigation use. These factors result in Lovelock being extremely susceptible to instances of prolonged drought, and exhibiting large fluctuations in annual ET. This work clearly illustrates that agricultural consumptive use is a function of water supply, weather, and land use change, which is useful in distinguishing how prolonged droughts and changing climate will potentially affect different hydrographic areas and agricultural communities in the future