Determination of any pure spatial qudits from a minimum number of measurements by phase-stepping interferometry

We present a proof-of-principle demonstration of a method to characterize any pure spatial qudit of arbitrary dimension d, which is based on the classic phase-shift interferometry technique. In the proposed scheme a total of only 4d measurement outcomes are needed, implying a significant reduction with respect to the standard schemes for quantum-state tomography which require on the order of d^2. By using this technique, we have experimentally reconstructed a large number of states ranging from d=2 up to 14 with mean fidelity values higher than 0.97. For that purpose the qudits were codified in the discretized transverse-momentum position of single photons, once they are sent through an aperture with d slits. We provide an experimental implementation of the method based in a Mach-Zehnder interferometer, which allows one to reduce the number of measurement settings to four since the d slits can be measured simultaneously. Furthermore, it can be adapted to consider the reconstruction of the unknown state from the outcome frequencies of 4d−3 fixed projectors independently of the encoding or the nature of the quantum system, allowing one to implement the reconstruction method in a general experiment.Fil: Pears Stefano, Quimey Martín. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Departamento de Física; ArgentinaFil: Rebón, Lorena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Ledesma, Silvia Adriana. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Departamento de Física; ArgentinaFil: Iemmi, Claudio César. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Departamento de Física; Argentin

Generalized q -plates and alternative kinds of vector and vortex beams

We took a generalization of the conventional concept of the q-plate, allowing in its definition nonlinear functions of the azimuthal coordinate, and simulated the resulting fields of applying this kind of element to uniformly polarized input beams, both in the near-field (Fresnel diffraction) and the far-field (Fraunhofer diffraction) approximations. In general terms, when working in the near-field regime, the chosen function defines the output polarization structure for linearly polarized input beams and the phase of the output field for circularly polarized input beams. In the far-field regime, it is obtained that when there are nonlinearities in the azimuthal variable, the central singularity of the polarization field of a vector or vortex beam may divide into several singularities of lower topological charge, preserving the total charge. Depending on the chosen q-plate function, different particular behaviors on the output beam are observed, which offers a whole range of possibilities for creating alternative kinds of vector and vortex beams, as well as polarization critical points and singularity distributions.Fil: Vergara, Martín Alexis. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física. Laboratorio de Procesado de Imágenes; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Iemmi, Claudio César. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física. Laboratorio de Procesado de Imágenes; Argentin

Evaluation and correction of aberrations in an optical correlator by phase-shifting interferometry

We propose a new method for evaluating and correcting aberrations in a Vander Lugt correlator. The technique is achieved with liquid-crystal displays of the correlator and allows the task to be performed in situ. We present the theory on which the method is based and the experimental results that we obtained by applying it in a convergent correlator

Optimization and performance criteria of a Stokes polarimeter based on two variable retarders

In this paper we present the analysis, optimization and implementation of several Stokes polarimeter configurations based on a setup including two variable retarders. The polarimeter analysis is based on the Mueller-Stokes formalism, and as a consequence, it is suitable to deal with depolarized light. Complete Stokes polarimeters are optimized by minimizing the amplification of simulated errors into the final solution. Different indicators useful to achieve this aim, as the condition number or the equally weighted variance, are compared in this paper. Moreover, some of the optimized polarimeters are experimentally implemented and it is studied the influence of small deviations from the theoretical ones on the amplification of the Stokes component error. In addition, the benefit of using incomplete polarimeters, when detecting specific ranges of states of polarization, is discussedFil: Peinado, Alba. Universitat Autonoma de Barcelona; EspañaFil: Lizana, Ángel. Universitat Autonoma de Barcelona; EspañaFil: Vidal, Josep. Universitat Autonoma de Barcelona; España. ALBA Synchrotron Light Source Facility; EspañaFil: Iemmi, Claudio Cesar. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Campos, Juan. Universitat Autonoma de Barcelona; Españ

Microparticle manipulation and imaging through a self-calibrated liquid crystal on silicon display

We present in this paper a revision of three different methods we conceived in the framework of liquid crystal on silicon (LCoS) display optimization and application. We preliminarily demonstrate an LCoS self-calibration technique, from which we can perform a complete LCoS characterization. In particular, two important characteristics of LCoS displays are retrieved by using self-addressed digital holograms. On the one hand, we determine its phase-voltage curve by using the interference pattern generated by a digital two-sectorial split-lens configuration. On the other hand, the LCoS surface profile is also determined by using a self-addressed dynamic micro-lens array pattern. Second, the implementation of microparticle manipulation through optical traps created by an LCoS display is demonstrated. Finally, an LCoS display based inline (IL) holographic imaging system is described. By using the LCoS display to implement a double-sideband filter configuration, this inline architecture demonstrates the advantage of obtaining dynamic holographic imaging of microparticles independently of their spatial positions by avoiding the non-desired conjugate images

Point diffraction interferometer with a liquid crystal monopixel

In this work a novel point diffraction interferometer based on a variable liquid crystal wave plate (LCWP) has been implemented. The LCWP consists of a 3x3 cm2 monopixel cell with parallel alignment. The monopixel cell was manufactured such that the electrode covers the entire surface except in a centered circular area of 50 μm of diameter. This circle acts as a point perturbation which diffracts the incident wave front giving rise to a spherical reference wave. By applying a voltage to the LCWP we can change the phase of the wave front that passes through the monopixel, except at the center. Phase shifting techniques are used in order to calculate the amplitude and phase distribution of the object wave front. The system allows a digital hologram to be obtained, and by using the Fresnel diffraction integral it is possible to digitally reconstruct the different planes that constitute the three dimensional object

Implementación de un interferómetro de difracción puntual con un monopíxel de cristal líquido

En este trabajo se presenta la implementación de un interferómetro por difracción puntual construido con un monopíxel de cristal líquido. En primer lugar se ha fabricado un monopíxel de cristal líquido con alineamiento paralelo de unas dimensiones de 3x3 cm2, en el que el electrodo cubre toda la superficie excepto en un orificio central de unas 50 ?m. Este orificio es el que actuará como punto difractor. Aplicando diferentes tensiones se puede cambiar la fase de la onda que llega al píxel en relación al punto central. Se ha construido un interferómetro con este elemento. Se captan 4 interferogramas con lo que se puede obtener la distribución de amplitud y fase de la onda. Se aplica este sistema para obtener un holograma digital y enfocar digitalmente diferentes planos de un objeto tridimensional

Determination of any pure spatial qudits from a minimum number of measurements by phase-stepping interferometry

We present a proof-of-principle demonstration of a method to characterize any pure spatial qudit of arbitrary dimension d, which is based on the classic phase-shift interferometry technique. In the proposed scheme a total of only 4d measurement outcomes are needed, implying a significant reduction with respect to the standard schemes for quantum-state tomography which require on the order of d2. By using this technique, we have experimentally reconstructed a large number of states ranging from d=2 up to 14 with mean fidelity values higher than 0.97. For that purpose the qudits were codified in the discretized transverse-momentum position of single photons, once they are sent through an aperture with d slits. We provide an experimental implementation of the method based in a Mach-Zehnder interferometer, which allows one to reduce the number of measurement settings to four since the d slits can be measured simultaneously. Furthermore, it can be adapted to consider the reconstruction of the unknown state from the outcome frequencies of 4d-3 fixed projectors independently of the encoding or the nature of the quantum system, allowing one to implement the reconstruction method in a general experiment.Instituto de Física La Plat