The Darboux transformation and the complex Toda lattice

It is well known that each solution of the Toda lattice can be represented by a tridiagonal matrix J(t). Under certain restrictions, it is possible to obtain some new solution by using the Darboux transformation of J(t) ¡ CI. Our goal is the extension of this fact, which is known for the real lattice, to high order complex Toda lattices as well as to the bi-infinite Toda lattice. In this latter case, we use the factorization LU for block-tridiagonal matrices

Non-Hermitian robust edge states in one-dimension: Anomalous localization and eigenspace condensation at exceptional points

Capital to topological insulators, the bulk-boundary correspondence ties a topological invariant computed from the bulk (extended) states with those at the boundary, which are hence robust to disorder. Here we put forward an ordering unique to non-Hermitian lattices, whereby a pristine system becomes devoid of extended states, a property which turns out to be robust to disorder. This is enabled by a peculiar type of non-Hermitian degeneracy where a macroscopic fraction of the states coalesce at a single point with geometrical multiplicity of $1$, that we call a phenomenal point.Comment: 6 pages, 4 figure

One-way quantum computing in superconducting circuits

We propose a method for the implementation of one-way quantum computing in superconducting circuits. Measurement-based quantum computing is a universal quantum computation paradigm in which an initial cluster-state provides the quantum resource, while the iteration of sequential measurements and local rotations encodes the quantum algorithm. Up to now, technical constraints have limited a scalable approach to this quantum computing alternative. The initial cluster state can be generated with available controlled-phase gates, while the quantum algorithm makes use of high-fidelity readout and coherent feedforward. With current technology, we estimate that quantum algorithms with above 20 qubits may be implemented in the path towards quantum supremacy. Moreover, we propose an alternative initial state with properties of maximal persistence and maximal connectedness, reducing the required resources of one-way quantum computing protocols.Comment: 5+2 pages, 4 figure

Quantum mechanical description of Stern-Gerlach experiments

The motion of neutral particles with magnetic moments in an inhomogeneous magnetic field is described in a quantum mechanical framework. The validity of the semi-classical approximations which are generally used to describe these phenomena is discussed. Approximate expressions for the evolution operator are derived and compared to the exact calculations. Focusing and spin-flip phenomena are predicted. The reliability of Stern-Gerlach experiments to measure spin projections is assessed in this framework.Comment: 12 pages, 7 eps figures included, revtex, submitted to PR

Versatile Wideband Balanced Detector for Quantum Optical Homodyne Tomography

We present a comprehensive theory and an easy to follow method for the design and construction of a wideband homodyne detector for time-domain quantum measurements. We show how one can evaluate the performance of a detector in a specific time-domain experiment based on electronic spectral characteristic of that detector. We then present and characterize a high-performance detector constructed using inexpensive, commercially available components such as low-noise high-speed operational amplifiers and high-bandwidth photodiodes. Our detector shows linear behavior up to a level of over 13 dB clearance between shot noise and electronic noise, in the range from DC to 100 MHz. The detector can be used for measuring quantum optical field quadratures both in the continuous-wave and pulsed regimes with pulse repetition rates up to about 250 MHz.Comment: 11 pages, 8 figures, 1 tabl

Potencial Analítico de los Polímeros de Impronta Molecular (MIPs) como Elementos de Reconocimiento Biomimético

Los polímeros de impronta molecular (MIPs) son materiales sintéticos que presentan propiedades de reconocimiento molecular específico hacia determinados compuestos. Estos materiales con “memoria selectiva” presentan un elevado potencial analítico como sustitutos de elementos de reconocimiento de origen biológico para el desarrollo de sensores, como sorbentes en procesos de extracción en fase sólida (SPE) y como fases estacionarias para HPLC y CE. La síntesis de estos materiales se basa en la formación de una estructura polimérica, altamente entrecruzada, alrededor de una molécula que actúa como plantilla que se extrae después de la polimerización. De esta forma, el MIP contendrá sitios de unión que son complementarios a la molécula plantilla en forma, tamaño y distribución de grupos funcionales que permiten su reconocimiento posterior, de forma selectiva Los MIPs suelen presentar ventajas interesantes en comparación con los receptore

Risk of spontaneous preterm birth in relation to maternal experience of serious life events during pregnancy

Background: The purpose of this study was to examine the risk of preterm birth (PTB) in relation to serious life events experienced during pregnancy in Peruvian women. Methods: This case-control study included 479 PTB cases and 480 term controls. In-person interviews asked information regarding sociodemographics, medical and reproductive histories, and serious life events experienced during pregnancy. Multivariate logistic regression procedures were used to estimate adjusted odds ratios (ORs) and 95% confidence intervals (CIs). Results: Compared with women who did not experience a serious life event during pregnancy, those who experienced the following life events had a more than two-fold increased odds of PTB: death of first-degree relative (adjusted OR 2.10; 95% CI 1.38–3.20), divorce or separation (adjusted OR 2.09; 95% CI 1.10–4.00), financial troubles (adjusted OR 2.70; 95% CI 1.85–3.94), or serious fight with partner (adjusted OR 2.40; 95% CI 1.78–3.17). Women who experienced any serious life events during pregnancy had higher odds (adjusted OR 2.29; 95% CI 1.65–3.18) of suffering spontaneous preterm labor and preterm premature rupture of membranes (adjusted OR 2.19; 95% CI 1.56–3.08), compared with women who did not experience any such events. Associations of similar directions and extent were observed for severity of PTB (ie, very, moderate, or late PTB). The magnitude of the associations increased as increased frequency of serious life events (Ptrend <0.001). Conclusion: Experiencing serious life events during pregnancy was associated with increased odds of PTB among Peruvian women. Interventions aimed at assisting women experiencing serious life events may reduce the risk of PTB. Future studies should include objective measures of stress and stress response to understand better the biological underpinnings of these associations