Progress toward scalable tomography of quantum maps using twirling-based methods and information hierarchies

We present in a unified manner the existing methods for scalable partial quantum process tomography. We focus on two main approaches: the one presented in Bendersky et al. [Phys. Rev. Lett. 100, 190403 (2008)], and the ones described, respectively, in Emerson et al. [Science 317, 1893 (2007)] and L\'{o}pez et al. [Phys. Rev. A 79, 042328 (2009)], which can be combined together. The methods share an essential feature: They are based on the idea that the tomography of a quantum map can be efficiently performed by studying certain properties of a twirling of such a map. From this perspective, in this paper we present extensions, improvements and comparative analyses of the scalable methods for partial quantum process tomography. We also clarify the significance of the extracted information, and we introduce interesting and useful properties of the $\chi$-matrix representation of quantum maps that can be used to establish a clearer path toward achieving full tomography of quantum processes in a scalable way.Comment: Replaced with published version (only minor changes respect to the first version

La siringomielia como factor de riesgo en la cirugía vertebral: Utilidad de los potenciales evocados intraoperatorios en un caso

Toda intervención quirúrgica sobra la columna vertebral conlleva un riesgo de lesión medular. Éste se multiplica cuando existe una patología medular de base. En los últimos años, gracias a la aparición de la monitorización neurofisiológica intraoperatoria, las complicaciones neurológicas intraoperatorias han disminuido. En el siguiente artículo, exponemos un caso de escoliosis secundaria a sirigomielia, en el que gracias al uso de potenciales evocados durante la cirugía, se han podido evitar lesiones neurológica irreversibles.Surgical correction of spinal deformities entails a risk of medullary dramage, and this can be higher when medullar pathology is associated. In last years, intraoperative neurological complications have decreased thanks to the intraoperative monitoring of neurophysiological parameters. In this work, we review a patient with scoliosis secondary to syringomyelia. The use of somatosensory evoked potentials during surgery allowed avoiding irreversible neurological complications

A new class of cyclin dependent kinase in chlamydomonas is required for coupling cell size to cell division

Citation: Li, Y., Liu, D., López-Paz, C., Olson, B. J. S. C., & Umen, J. G. (2016). A new class of cyclin dependent kinase in chlamydomonas is required for coupling cell size to cell division. eLife, 5(MARCH2016). doi:10.7554/eLife.10767Proliferating cells actively control their size by mechanisms that are poorly understood. The unicellular green alga Chlamydomonas reinhardtii divides by multiple fission, wherein a ‘counting’ mechanism couples mother cell-size to cell division number allowing production of uniform-sized daughters. We identified a sizer protein, CDKG1, that acts through the retinoblastoma (RB) tumor suppressor pathway as a D-cyclin-dependent RB kinase to regulate mitotic counting. Loss of CDKG1 leads to fewer mitotic divisions and large daughters, while mis-expression of CDKG1 causes supernumerous mitotic divisions and small daughters. The concentration of nuclear-localized CDKG1 in pre-mitotic cells is set by mother cell size, and its progressive dilution and degradation with each round of cell division may provide a link between mother cell-size and mitotic division number. Cell-size-dependent accumulation of limiting cell cycle regulators such as CDKG1 is a potentially general mechanism for size control. © Li et al

Tratamiento quirúrgico de la pseudoartrosis de la apófisis odontoides: Presentación de dos casos

Se presenta nuestra experiencia de dos casos de pseudoartrosis de apófisis odontoides tratadas quirúrgicamente mediante atornillado directo a compresión por vía anterior paraesternomocleidomastoidea. El resultado final fue satisfactorio en el primer caso, teniendo que realizarse una artrodesis posterior C1-C2 en el segundo. Se discute la posibilidad de un exceso de angulación posterioSe presenta nuestra experiencia de dos casos de pseudoartrosis de apófisis odontoides tratadas quirúrgicamente mediante atornillado directo a compresión por vía anterior paraesternomocleidomastoidea. El resultado final fue satisfactorio en el primer caso, teniendo que realizarse una artrodesis posterior C1-C2 en el segundo. Se discute la posibilidad de un exceso de angulación posterior en la colocación del tornillo como causa del fracaso de la técnica.en la colocación del tornillo como causa del fracaso de la técnica.Two cases of odontoid process non-union treated by direct screw compression through an anterior approach are presented. The outcome was satisfactory in one case. The other required posterior C1-C2 union because of anterior screwing failure. An excessive posterior angulation of the screw thought to be the cause of anterior fusion failure

Análisis del plano sagital en las escoliosis idiopáticas tratadas con instrumentación Cotrel-Dubousset

Se analiza la evolución del plano sagital en 50 enfermos con escoliosis idiopática intervenidos mediante artrodesis posterior con instrumentación de Cotrel-Dubousset con un seguimiento medio de 72 meses. Se recogieron los valores evolutivos de cifosis torácica medida entre T5 y T12 y de lordosis lumbar medida entre Ll y L5. Las curvas escolióticas fueron clasificadas según King et al. Los resultados obtenidos mostraron que no existía una variación global significativa de la cifosis torácica tras la cirugía. Sólo en aquellos enfermos que previamente existía una hipocifosis torácica existía una mejoría estadísticamente significativa de la misma con la intervención. Se evidenció una clara tendencia al incremento de la cifosis torácica con el tiempo. La lordosis lumbar se mantuvo, en la mayoría de los casos, dentro de límites fisiológicos. La instrumentación de Cotrel-Dubousset ofrece ventajas evidentes respecto a instrumentaciones previas en lo que respecta a la obtención de una curva más fisiológica en el plano sagital. Permite corregir la hipocifosis torácica severa y mantener la lordosis lumbar dentro de límites normales, incluso en instrumentaciones por debajo de L3.Sagittal plane analysis of 50 patients with idiopathic scoliosis treated with Cotrel- Dubousset instrumentation was performed. Mean follow-up was 72 months. The values of thoracic kyphosis from T5 to T12 and lumbar lordosis from L1 to L5 were retrospectively reviewed. Scoliotic curves were classified according to King et al. The results showed that there was not any significant change in thoracic kyphosis after surgery. Only those patients with preoperative thoracic hypokyphosis achieved a significant realignment. There was an obvious increase of thoracic kyphosis with time. Lumbar lordosis was maintained within normal limits in the mayority of patients. Cotrel-Dubousset instrumentation achieves better sagittal alignment than previous systems. It corrects thoracic hypokyphosis and preserves lumbar lordosis, even when the instrumentation is carried out lower than L3

Avulsión de la tuberosidad anterior de la tibia asociada a rotura del tendón cuadricipital

Se presenta 1 caso de fractura-avulsión de la tuberosidad anterior de la tibia asociada a rotura del tendón cuadricipital en un varón de 16 años. Tras el tratamiento quirúrgico de la fractura tuberositaria, y a pesar de haber pasado inicialmcnte inadvertida la lesión tendinosa, el resultado final a los 9 meses ha sido satisfactorio.A case of avulsion-fracture of the anterior tibial tubercle associated with rupture of the cuadricipital tendon in a 16-ycars-old boy is presented. After surgical treatment, in spite of having overlooked initially the tendinous lesion, the functional result at 9 months follow-up has been satisfactory

A Method for Modeling Decoherence on a Quantum Information Processor

We develop and implement a method for modeling decoherence processes on an N-dimensional quantum system that requires only an $N^2$-dimensional quantum environment and random classical fields. This model offers the advantage that it may be implemented on small quantum information processors in order to explore the intermediate regime between semiclassical and fully quantum models. We consider in particular $\sigma_z\sigma_z$ system-environment couplings which induce coherence (phase) damping, though the model is directly extendable to other coupling Hamiltonians. Effective, irreversible phase-damping of the system is obtained by applying an additional stochastic Hamiltonian on the environment alone, periodically redressing it and thereby irreversibliy randomizing the system phase information that has leaked into the environment as a result of the coupling. This model is exactly solvable in the case of phase-damping, and we use this solution to describe the model's behavior in some limiting cases. In the limit of small stochastic phase kicks the system's coherence decays exponentially at a rate which increases linearly with the kick frequency. In the case of strong kicks we observe an effective decoupling of the system from the environment. We present a detailed implementation of the method on an nuclear magnetic resonance quantum information processor.Comment: 12 pages, 9 figure