Narrowband Photon Pair Source for Quantum Networks

We demonstrate a compact photon pair source based on a periodically poled lithium niobate nonlinear crystal in a cavity. The cavity parameters are chosen such that the emitted photon pair modes can be matched in the region of telecom ultra dense wavelength division multiplexing (U-DWDM) channel spacings. This approach provides efficient, low-loss, mode selection that is compatible with standard telecommunication networks. Photons with a coherence time of 8.6 ns (116 MHz) are produced and their purity is demonstrated. A source brightness of 134 pairs(s.mW.MHz)$^{-1}$ is reported. The high level of purity and compatibility with standard telecom networks is of great importance for complex quantum communication networks

Scaling up MIMO Radar for Target Detection

This work focuses on target detection in a colocated MIMO radar system. Instead of exploiting the »classical' temporal domain, we propose to explore the spatial dimension (i.e., number of antennas M) to derive asymptotic results for the detector. Specifically, we assume no a priori knowledge of the statistics of the autoregressive data generating process and propose to use a mispecified Wald-type detector, which is shown to have an asymptotic χ-squared distribution as M → ∞. Closed-form expressions for the probabilities of false alarm and detection are derived. Numerical results are used to validate the asymptotic analysis in the finite system regime. It turns out that, for the considered scenario, the asymptotic performance is closely matched already for M ≥ 50

Absolute frequency measurements of 85Rb nF7/2 Rydberg states using purely optical detection

A three-step laser excitation scheme is used to make absolute frequency measurements of highly excited nF7/2 Rydberg states in 85Rb for principal quantum numbers n=33-100. This work demonstrates the first absolute frequency measurements of rubidium Rydberg levels using a purely optical detection scheme. The Rydberg states are excited in a heated Rb vapour cell and Doppler free signals are detected via purely optical means. All of the frequency measurements are made using a wavemeter which is calibrated against a GPS disciplined self-referenced optical frequency comb. We find that the measured levels have a very high frequency stability, and are especially robust to electric fields. The apparatus has allowed measurements of the states to an accuracy of 8.0MHz. The new measurements are analysed by extracting the modified Rydberg-Ritz series parameters.Comment: 12 pages, 5 figures, submitted to New. J. Phy

Employment protection legislation, labor courts, and effective firing costs

In many countries, labor courts play a central role in the determination of firing costs by monitoring and supervising the procedures for dismissals, and, eventually, deciding severance payments mandated by the employment protection legislation (EPL). To get some insights about the impact of labor courts on effective firing costs, we explore a new database that contains information on labor courts' intervention in firings before and after the implementation of significant EPL reforms modifying severance payments and procedures for dismissals. Our results suggest that labor court rulings on economic dismissals did not fully translate the reduction of firing costs mandated by the new EPL to effective firing costs

Employment protection legislation and labor court activity in Spain

La intervención de los juzgados de lo Social en casos de despido da lugar a que pueda existir una diferencia importante entre las indemnizaciones por despido establecidas por la ley y los costes efectivos de despido (después de su resolución). Además de los costes asociados al procedimiento judicial, están los derivados de la incertidumbre sobre el sentido de la sentencia, que puede declarar el despido improcedente, lo que implica una subida sustancial de las indemnizaciones. En 2010 y 2012 sendas reformas laborales ampliaron la definición de despido objetivo procedente en España. En este artículo se usan datos provinciales sobre sentencias judiciales en casos de despido referidos a períodos anteriores y posteriores a la reforma (2004-2014). En este análisis se tienen en cuenta algunas características provinciales (las condiciones locales del mercado de trabajo, características de los juzgados de lo Social, la prevalencia de conciliaciones judiciales, la congestión judicial) que pueden influir en la selección de casos de despido que acaban siendo resueltos por sentencia judicial. Los resultados indican que, a pesar de las reformas de 2010 y 2012, la proporción de despidos que son declarados procedentes por los juzgados de lo Social no ha aumentado significativamente, aunque ahora muestra una asociación negativa con la tasa de paro local menor que en el periodo anterior a las reformasLabor courts may introduce a significant wedge between “legal” firing costs and “effective” (post-trial) firing costs. Apart from procedural costs, there is uncertainty over judges’ rulings, in particular over the likelihood of a “fair” dismissal ultimately being ruled as “unfair”, which may increase fi ring costs significantly. In 2010 and 2012, reforms of Employment Protection Legislation widened the definition of fair economic dismissals in Spain. In this paper we look at Labor Court rulings on dismissals across Spanish provinces before and after the EPL reforms (2004-2014). We make this comparison taking into account a set of co-variates (local labor market conditions, characteristics of the Labor Courts, pre-trial conciliations, congestion of Labor Courts) which may determine the selection of dismissal cases ruled by Labor Courts. Our results suggest that, despite the 2010 and 2012 EPL reforms, the proportion of economic redundancies being ruled as fair by Labor Courts has not substantially increased, although it is now less negatively associated with the local unemployment rate than in the pre-reform perio

Massive MIMO radar for target detection

Since the seminal paper by Marzetta from 2010, the Massive MIMO paradigm in communication systems has changed from being a theoretical scaled-up version of MIMO, with an infinite number of antennas, to a practical technology. Its key concepts have been adopted in the 5G new radio standard and base stations, where 64 fully-digital transceivers have been commercially deployed. Motivated by these recent developments, this paper considers a co-located MIMO radar with MT transmitting and MR receiving antennas and explores the potential benefits of having a large number of virtual spatial antenna channels N=MTMR. Particularly, we focus on the target detection problem and develop a robust Wald-type test that guarantees certain detection performance, regardless of the unknown statistical characterization of the disturbance. Closed-form expressions for the probabilities of false alarm and detection are derived for the asymptotic regime N→∞. Numerical results are used to validate the asymptotic analysis in the finite system regime with different disturbance models. Our results imply that there always exists a sufficient number of antennas for which the performance requirements are satisfied, without any a-priori knowledge of the disturbance statistics. This is referred to as the Massive MIMO regime of the radar system

Picosecond Nonlinear Relaxation of Photoinjected Carriers in a Single GaAs/AlGaAs Quantum Dot

Photoemission from a single self-organized GaAs/AlGaAs quantum dot (QD) is temporally resolved with picosecond time resolution. The emission spectra consisting of the multiexciton structures are observed to depend on the delay time and the excitation intensity. Quantitative agreement is found between the experimental data and the calculation based on a model which characterizes the successive relaxation of multiexcitons. Through the analysis we can determine the carrier relaxation time as a function of population of photoinjected carriers. Enhancement of the intra-dot carrier relaxation is demonstrated to be due to the carrier-carrier scattering inside a single QD.Comment: 4 pages, 4 figures, to be published in Phys. Rev. B, Rapid

Effects of random alloy disorder, shape deformation, and substrate misorientation on the exciton lifetime and fine structure splitting of GaAs/AlxGa1-xAs(111) quantum dots

Using atomistic, million-atom screened pseudopotential theory together with configuration interaction, as well as atomically resolved structures based on experimental characterization, we perform numerical calculations on self-assembled GaAs/AlxGa1-xAs(111) quantum dots that we compare with our experimental data. We show that random alloy disorder in the barrier can cause a symmetry breaking at the single-particle level (distortions of wave functions and lifting of degeneracies) which translates into the appearance of a nonzero exciton fine structure splitting (FSS) at the many-body level. Nevertheless, our results indicate that varying the concentration of aluminum in the random alloyed barrier allows simultaneous tuning of the exciton fine structure splitting and emission wavelength without altering its radiative lifetime tau approximate to 200 ps. Additionally, the optical properties of these quantum dots are predicted to be very robust against both symmetric and asymmetric shape elongation (with FSS 2.2 mu eV), rendering postselection less essential under well-controlled growth conditions. On the other hand, the growth on miscut substrates introduces a structural anisotropy along the quantization axis to which the system is very sensitive: the FSS ranges between 5 and 50 mu eV while the radiative lifetime of the transition is increased up to tau = 400 ps. The numerical results for the FSS are in perfect agreement with our experimental measurements which give FSS = 10 +/- 9 mu eV for 2 degrees miscut angle at x = 0.15

Pervivencia del Derecho Inca Prehispánico

El artículo refiere a la presencia del derecho de gentes[1] en su etapa prehispánica como noción y sostenibilidad en el tiempo, en un primer momento, se menciona el origen y la existencia del derecho desde su concepción hasta nuestros días, y en un segundo escenario la organización como estado y toda su estructura; pues lo cierto es que el derecho cohabitará con el hombre hasta que el perviva y seguirá siendo parte de una sociedad constituyendo así su natural estado de organización colectiva. Entonces, aproximándonos al tema que trataremos en este postulado nos detendremos en el tiempo y en la época en la que todavía no se habría interpuesto la transculturación entre dos mundos (Europa y América). Entonces nuestra propuesta está planteada desde la fundamentación objetiva enfatizando la existencia del “derecho incaico”. Para ello, primeramente, debemos referir organización y estado, luego al sistema regulatorio que este tuvo; siendo este, el segundo una consecuencia preexistente de la conducta humana. Pues bien, bajo esa afirmación llegamos a concluir la posible existencia del derecho inca o incaico, a razón de que el estado conformado por el Tahuantinsuyo estuvo compuesto de reformas sustentos jurídicos donde existieron regla y prohibiciones, normas y principios per se. Entonces visto desde la analítica interpretativa o mejor dicho desde la óptica lógica jurídica entendemos que a esto se hace referencia el compuesto de un sistema jurídico completo. Pues bien, visualizando las razones ya existentes coadyuvarían a esta propuesta planteada el sustento de nuestro análisis incidiendo en la confirmación sobre la supervivencia del derecho inca en el Tahuantinsuyo, constituyendo esto un tópico más de estudio siendo parte de la Historia del Derecho en el Perú. Por lo que, la propuesta planteada estaría basada en razones lógicas al tema, pues se sustenta en otras investigaciones planteadas por historiadores y cronistas e historiadores del derecho que también buscan hacer un análisis mucho más verosímil. &nbsp