Papers by Alejandro Hnilo
arXiv (Cornell University), Aug 10, 2020
A fin de posibilitar el micromaquinado láser de distintas imágenes 2D sobre sustratos de silicio,... more A fin de posibilitar el micromaquinado láser de distintas imágenes 2D sobre sustratos de silicio, se diseñó un Sistema Automático por Software que permite en líneas generales: analizar y procesar digitalmente en tiempo real cualquier imagen salvaguardada en formato de mapa de bits monocromático, que posteriormente será micromaquinada; controlar mediante comunicación serial una plataforma x-y motorizada que mediante el desplazamiento micrométrico de la posición del punto de enfoque sobre la muestra posibilita el micromaquinado láser de la imagen; modificar la frecuencia de repetición como así también la manipulación de la cavidad láser. Palabras clave: micromaquinado, láser. In order to enable the laser micromachining of different 2D images on silicon substrates, it was designed an Automatic System which allows, broadly speaking: to analyze and digitally process in real time any image safeguarded in monochromatic bitmap format that subsequently will be micromachined; to control, through serial communication, the motorized x-y platform which by micrometrically moving the position of the focus point over the sample will make possible the laser micromachining; to modify the repetition frequency as well as the manipulation of the laser cavity.
En ocasión de las Reuniones AFA del año 2007 y 2009, informamos acerca de las dificultades encont... more En ocasión de las Reuniones AFA del año 2007 y 2009, informamos acerca de las dificultades encontradas y de los avances parciales obtenidos en pos de la construcción de un láser de estado sólido cuyo medio activo consistiera de una delgada lámina de Nd en vidrio iluminada con una batería de diodos láser. El propósito de esa primera etapa del proyecto era avanzar posteriormente en el diseño y operación de un láser de pulsos ultracortos que aprovechara por un lado la geometría del medio activo, y por otro el gran ancho de banda que presenta el Nd al emplear vidrio cómo medio soporte, a fin de obtener pulsos de muy corta duración. En esta oportunidad informamos acerca de la obtención por vez primera de dicho dispositivo operando finalmente cómo emisor láser, incluyendo los detalles de diseño que permitieron alcanzar el umbral de operación láser, y caracterizando el dispositivo a través de sus principales parámetros de funcionamiento de acuerdo a los ensayos practicados hasta el momento. Palabras clave: Nd:Vidrio, laser en forma de lámina In the 2007 and 2009 AFA meetings we have reported the difficulties afforded and the partial advances obtained in order to build a solid state laser based on a thin slab of Neodymium doped Glass pumped by a diode stack laser. The purpose of these first steps was to design and operate a new ultra-short pulsed laser, taking advantage of a particular geometry for the active medium and the wide bandwidth provided by the Neodymium ion when Glass is used as the support material, in order to get pulses having very short duration. In this case we report for the first time laser emission obtained with our own design, including relevant details to get laser threshold. Laser characterization was performed recently by measuring the most important operating parameters of this configuration.
Applied Optics, Apr 14, 2023
The generation of series of random numbers is an important and difficult problem. Even the very d... more The generation of series of random numbers is an important and difficult problem. Even the very definition of "random" is difficult. Appropriate measurements on entangled states have been proposed as the definitive solution to produce series of certified randomness. However, several reports indicate that quantum-based devices show a disappointing rate of series rejected by standard tests of randomness. This problem is usually solved by using algorithms named extractors but, if the extractor were known by an eavesdropper (a situation that cannot be ruled out) the key's security in QKD setups may be menaced. We use a "toy" fiber-optic-based setup, similar to a QKD one to be used in the field, to generate binary series, and evaluate their level of randomness according to Ville's principle. Series are tested with a battery of standard statistical indicators, Hurst exponent, Kolmogorov complexity, minimum entropy, Takens' dimension of embedding, and Augmented Dickey-Fuller and Kwiatkowski-Phillips-Schmidt-Shin to check stationarity. A theoretically predicted relationship between complexity and minimum entropy is observed. The good performance of a simple method to get useful series from rejected series, reported by Solis et al., is confirmed and supported with additional arguments. Regarding QKD, the level of randomness of series obtained by applying Toeplitz's extractor to rejected series is found to be indistinguishable from the level of non-rejected raw ones.
Research Square (Research Square), Aug 17, 2022
Anales AFA, 2014
A fin de posibilitar el micromaquinado láser de distintas imágenes 2D sobre sustratos de silicio,... more A fin de posibilitar el micromaquinado láser de distintas imágenes 2D sobre sustratos de silicio, se diseñó un Sistema Automático por Software que permite en líneas generales: analizar y procesar digitalmente en tiempo real cualquier imagen salvaguardada en formato de mapa de bits monocromático, que posteriormente será micromaquinada; controlar mediante comunicación serial una plataforma x-y motorizada que mediante el desplazamiento micrométrico de la posición del punto de enfoque sobre la muestra posibilita el micromaquinado láser de la imagen; modificar la frecuencia de repetición como así también la manipulación de la cavidad láser. Palabras clave: micromaquinado, láser. In order to enable the laser micromachining of different 2D images on silicon substrates, it was designed an Automatic System which allows, broadly speaking: to analyze and digitally process in real time any image safeguarded in monochromatic bitmap format that subsequently will be micromachined; to control, through serial communication, the motorized x-y platform which by micrometrically moving the position of the focus point over the sample will make possible the laser micromachining; to modify the repetition frequency as well as the manipulation of the laser cavity.
Anales AFA, 2020
En el presente trabajo, se describe el desarrollo en la plataforma LabVIEW junto con el entorno d... more En el presente trabajo, se describe el desarrollo en la plataforma LabVIEW junto con el entorno de programación de MATLAB para el control y automatización de experimentos de óptica cuántica. El programa desarrollado, permite la comunicación con los diferentes dispositivos involucrados: detectores SPCM (Single Photon Counters Modules) de fotones; conversor TDC (time to digital converter) ID900 de ID Quantique con resolución de 10 ps y rotadores motorizados PRM1Z8 (Motorized Rotation Stage de Thorlabs). El sistema implementado, permite trabajar de forma óptima durante los experimentos de laboratorio que deben realizarse en la oscuridad, evitando errores de manipulación durante el proceso de medición. Palabras clave: automatización, control, óptica cuántica. In this paper, it is described the development in the LabVIEW plataform together with the programming context of MATLAB for the control and automation of quantum optics experiments. The developed program allows the communication of the different involved devices: SPCM (Single Photon Counters Modules) photon detectors; TDC (time to digital converter) converter ID900 from ID Quantique with 10 ps of resolution and the motorized rotators PRM1Z8 (Motorized Rotation Stage from Thorlabs). The implemented system, allows to work optimally during the laboratory experiments that must be performed under darkness condition, this avoids manipulation errors during the measurement process.
arXiv (Cornell University), May 20, 2020
The experimentally verified violation of Bell's inequalities apparently implies that at least one... more The experimentally verified violation of Bell's inequalities apparently implies that at least one of two intuitive beliefs, which are accepted as true in almost all scientific practice, must be false: that effects propagating at infinite velocity do not exist, and that natural phenomena occur independently of being observed. Giving up any one of these two beliefs (usually known together as Local Realism) is controversial. Many theories have been proposed to reconcile the observed violation of Bell's inequalities with Local Realism, but none has been fully successful. In this paper, it is recalled that Bell's inequalities are equivalent to the conditions to decide the completeness of a theory according to Boolean logic. Therefore, any theory aimed to violate Bell's inequalities must start by giving up Boolean logic. The problem is hence split in two: the "soft" problem is to explain the violation of Bell's inequalities without violating (non-Boolean) Local Realism. The "hard" problem is to predict the time values when single particles are detected, in such a way that the resulting number of coincidences violates Bell's inequalities. A simple hidden variables model is introduced, which solves the "soft" problem in an even ideally perfect setup. This is possible thanks to the use of vectors in real space as the hidden variables and the corresponding operation (projection), which do not hold to Boolean logic. This model reconciles the violation of Bell's inequalities with Local Realism and should end decades of controversy. Regarding the "hard" problem, the introduced model is as incomplete as Quantum Mechanics is. It is argued that solving the "hard" problem involves devising a new kind of quantum computer, which should be able to accept (non-Boolean) hidden variable values as input data and replace the statistical Born's rule of usual Quantum Mechanics with a deterministic threshold condition.
arXiv (Cornell University), Feb 25, 2014
The Bell's inequalities are derived from the hypotheses of Locality, Realism and (what is lesser ... more The Bell's inequalities are derived from the hypotheses of Locality, Realism and (what is lesser known) the equality between the factual and the counterfactual time averages of the expectation values of observables. The necessity of a hypothesis additional to Local Realism opens a promising way out to the old controversy between Quantum Mechanics and Local Realism. For, it is possible to speculate that it is this additional hypothesis, and not Local Realism, what is disproved in the experiments reporting the violation of the Bell's inequalities. Yet, there are doubts on how the additional hypothesis may be violated in a physically reasonable process. A simple example showing that this is possible, the relationship between the validity of the additional hypothesis and the validity of the Bell's inequalities, and considerations on its physical meaning, are presented.
arXiv (Cornell University), Jun 23, 2015
The "disentanglement eraser" or "entanglement restorer" scheme allows retrieving entanglement by ... more The "disentanglement eraser" or "entanglement restorer" scheme allows retrieving entanglement by erasing the information about the formation of a classical (or separable) state. It implies a close analogy between the pairs of properties: entangled-separable and waveparticle, the latter as it is described in the well known "quantum eraser" scheme. Both schemes illustrate the physical importance of information in quantum systems. The disentanglement eraser is also useful as a building block in quantum information and computation. Its full optical implementation using three-photons decay in a centro-symmetrical crystal is proposed. It seems technically simpler to achieve than the known proposed alternatives.
Broadband second harmonic parametric scattering in ferroelectric crystals with random domains str... more Broadband second harmonic parametric scattering in ferroelectric crystals with random domains structure 12:30-13:30 Lunch Chair: Alan Shore 14:30-15:15 Luis Pesquera (Santander, Spain) Nonlinear dynamics reconstruction of chaotic cryptosystems based on a laser diode subject to optoelectronic feedback with fixed and variable delay 15:15-16:00 Laurent Larger (Besançon, France) The integro-differential delay electro-optic oscillator: new dynamical features and robust generalized synchronization capabilities with a delay shared feedback coupling 16:00-16:30 Yanne Chembo (Besançon, France) Stability properties of a pure microwave oscillation in a narrow band electrooptic delay oscillator
arXiv (Cornell University), Jun 23, 2015
The 'disentanglement eraser' or 'entanglement restorer' scheme allows retrieving entanglement by ... more The 'disentanglement eraser' or 'entanglement restorer' scheme allows retrieving entanglement by erasing the information about the formation of a classical (or separable) state. It suggests an analogy between the pairs of properties: entangled-separable and wave-particle, the latter as described in the 'quantum eraser'. The scheme illustrates the physical importance of information in quantum systems, and it is also useful as a building block for quantum computation. An optical setup for its simple implementation using three-photon decay in a centro-symmetrical crystal is proposed.
arXiv (Cornell University), Dec 22, 2012
The conflict between Quantum Mechanics (QM) and the intuitive concepts of Locality and Realism (L... more The conflict between Quantum Mechanics (QM) and the intuitive concepts of Locality and Realism (LR) is manifest in the correlation between measurements performed in remote regions of a spatially spread entangled state. In this paper, it is hypothesized that transient deviations (from the values predicted by QM) occur if the correlation is measured in a time shorter than L/c, where L is the spatial spread of the entangled state and c is the speed of light. In this way, the conflict is solved by changing QM minimally. Under general assumptions, it is obtained a mathematical model of the process that reproduces the QM value after a time longer than L/c has elapsed. One of the predictions of this model is that oscillations of the rate of coincidences should exist, with a main frequency lower than c/4L. An experiment able to reveal these oscillations is shown to be accessible, by placing stations at L≈5 Km and reaching a coincidence rate of ≈3×10 5 s-1 (a value already obtained at the laboratory scale). This means a test of QM vs LR of a completely new type, with several practical and theoretical advantages.
arXiv (Cornell University), Jun 6, 2013
By taking into account that all real measurements are performed successively, during time, it is ... more By taking into account that all real measurements are performed successively, during time, it is concluded that the violation of the Bell's inequalities in the Nature does not refute (even in an ideally perfect experiment) the theories holding to Local Realism, for an unavoidable additional assumption is involved. Yet, in order to be acceptable, such theories must predict different values for the factual and counterfactual time averages of probabilities or observables.
arXiv (Cornell University), Aug 14, 2023
The Bell's basis is composed of four maximally entangled states of two qubits, named Bell states.... more The Bell's basis is composed of four maximally entangled states of two qubits, named Bell states. They are usual tools in many theoretical studies and experiments. The aim of this paper is to find out the symmetries that determine a Bell state. For this purpose, starting from a general density matrix, physical constraints and symmetry conditions are added until the elements of the Bell's basis are univocally determined. It is found that the usual physical constraints and symmetry conditions do not suffice to determine a Bell state. The additional restriction needed is named here "atomic" symmetry. It is a sort of global symmetry of the system, not derived from the action = reaction law. It is also found that the imperfection in fulfilling the atomic symmetry is linearly proportional to the deviation of the Concurrence from its maximum value. The atomic symmetry allows a different insight on the nature of entanglement, and might be useful as a criterion to define the condition of maximal entanglement for states with more than two qubits.
arXiv (Cornell University), Feb 28, 2023
A new definition of "Realism" is proposed: it is that a gedanken "spectrograph" of hidden variabl... more A new definition of "Realism" is proposed: it is that a gedanken "spectrograph" of hidden variables behaves as an actual (say, wavelength) spectrograph. The question is: does this definition allow, by itself, the derivation of Bell's inequalities? If it were, then such a spectrograph would be impossible, for Bell's inequalities are observed to be violated. In this short paper it is reported that, on the contrary, such spectrograph is compatible with the violation of Bell's inequalities. This result puts some new light on the controversy about the hypotheses necessary to derive Bell's inequalities. In particular, "Spectrograph's Realism", and "Locality", are proven to be different, and both necessary, hypotheses to derive Bell's inequalities.
Anales AFA, Sep 19, 2014
En este trabajo se presentan los resultados de la comparación del micromaquinado láser de obleas ... more En este trabajo se presentan los resultados de la comparación del micromaquinado láser de obleas de silicio empleando la técnica de escritura directa (direct writing) con pulsos de nanosegundos generados por la técnica de Q-switch en Nd:YAG y pulsos de femtosegundos, provenientes del Ti:Zafiro mode lockeado. Se determinaron los efectos de la redeposición de escombros (debris) y se proponen técnicas para su control.
Optics Communications, Aug 1, 1999
ABSTRACT In a periodic optical system, the evolution of a gaussian beam of light, as well as of a... more ABSTRACT In a periodic optical system, the evolution of a gaussian beam of light, as well as of a short pulse, has a direct interpretation as an iterative map in the complex plane. Trajectories for arbitrary initial conditions and the general condition for the existence of fixed points of high periodicity were obtained. The cases of confined and unconfined beams and cavities with and without apertures are discussed. Among other applications, this approach promises to be fruitful for the description of Kerr lens mode locking lasers. As an illustration of this possibility, the rise of a collective behavior in a large number of maps coupled through a Kerr nonlinearity is shown.
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Papers by Alejandro Hnilo