Continuous Generation of Quantum Light from a Single Ground-State Atom in an Optical Cavity

We show an optical wave-mixing scheme that generates quantum light by means of a single three-level atom. The atom couples to an optical cavity and two laser fields that together drive a cycling current within the atom. Weak driving in combination with strong atom-cavity coupling induces transitions between the dark states of the system, accompanied by single-photon emission and suppression of atomic excitation by quantum interference. For strong driving, the system can generate coherent or Schr\"odinger cat-like fields with frequencies distinct from those of the applied lasers.Comment: 5 pages, 4 figure

Robustness of quantum discord to sudden death

We calculate the dissipative dynamics of two-qubit quantum discord under Markovian environments. We analyze various dissipative channels such as dephasing, depolarizing, and generalized amplitude damping, assuming independent perturbation, in which each qubit is coupled to its own channel. Choosing initial conditions that manifest the so-called sudden death of entanglement, we compare the dynamics of entanglement with that of quantum discord. We show that in all cases where entanglement suddenly disappears, quantum discord vanishes only in the asymptotic limit, behaving similarly to individual decoherence of the qubits, even at finite temperatures. Hence, quantum discord is more robust than the entanglement against to decoherence so that quantum algorithms based only on quantum discord correlations may be more robust than those based on entanglement.Comment: 4 figures, 4 page

Compresión medular por hipercifosis toracolumbar en un cuadro de displasia espondiloepifisaria congénita

En algunos casos de displasia espondiloepifisaria puede resultar difícil el diagnóstico diferencial de las alteraciones de la marcha por coexistir una cifosis angular severa con posible compromiso medular y una coxopatía importante. Cuando existe una compresión medular, el pronóstico generalmente es sombrío y es excepcional encontrar en la literatura una indicación quirúrgica favorable en este tipo de displasias. Presentamos 2 casos afectos de Displasia Espondiloepifisaria en los que se planteó el diagnóstico diferencial y se realizaron tratamientos quirúrgicos diferentes, obteniendo buenos resultados.The clinical findings in DEEC are: Disproportionate dwarfisms (with short spine, kyphoscoliosis, pectus carinatus), genu valgum, etc. The epiphyses are poorly ossified and deformed. Progressive motor weakness may be the first clinical symptom of spinal cord compression caused by a kyphoscoliosis. In these cases we must make a differential diagnosis with a premature osteoarthritis of the hips. We report two cases. One of them was treated with spinal fusion for correction of her kyphoscoliosis, and the other one with a total hip arthroplasty

Evolución de las curvas sagitales en pacientes afectos de escoliosis tratados con corsé de milwaukee

En una serie de 41 pacientes con escoliosis idiopática tratados ortopédicamente con corsé de Milwaukee, se analizó retrospectivamente el efecto del corsé en la evolución de la curva sagital torácica. El corsé no tuvo efecto lordosante en el 66% de los casos. El efecto lordosante se desarrolló con mayor frecuencia en pacientes menores de 12 años o con más de tres años de tratamiento; sin embargo, hubo pacientes que lo llevaron 5 años o más sin modificación alguna en la curva sagital. En conclusión, el corsé de Milwaukee tiene un efecto lordosante en tan sólo un tercio de los casos tratados. Los factores que favorecen la rectificación del raquis torácico parecen ser la larga duración del tratamiento y una colocación en edades tempranas, por debajo de los 12 años.A retrospective analysis was carried out in a group of 41 patients affected by idiopathic scoliosis treated by Milwaukee brace. The aim of the study was to asses the effect of the brace in the evolution of the thoracic sagital curve. We observed a higher frecuency of cases with thoracic lordosis in patients with less than 12 years of age, or in those treated for more than 3 years. There were cases who wore the brace for more than 5 years with no modification in the sagital curve. In conclusion, the Milwaukee brace induced a lordotic effect in just one third of patients treated for idiopathic scoliosis. The onset of treatment in patients under 12 years and long a periods of treatment should be considered as the predisponing factors for thoracic lordosis