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  • Photonic entanglement: new sources and new applications  Open access

     Svozilík, Jirí
    Universitat Politècnica de Catalunya
    Theses

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    Las correlaciones cuánticas, normalmente conocidas como entanglement, son uno de los temas más estudiados y discutidos de la Mecánica Cuántica, desde la introducción del concepto en la década de 1930. Incluso hoy en día, una gran cantidad de esfuerzos, tanto teóricos como experimentales, se dedican en este tema, que cubre muchas áreas distintas de la física, tales como medición cuántica (quantum metrology), computación cuántica (quantum computing), comunicaciones cuánticas (quantum communications), física de estado sólido, química e incluso biología. Las tareas fundamentales de investigación que uno debe considerar en relación con entrelazamiento son:-Cómo crear estados cuánticos entangled.-Cómo mantener el entanglement durante la propagación, en contra de las fuentes que pueden crear de-coherencia.-Cómo emplear los beneficios que el entanglement ofrece.Esta tesis, dividida en cuatro capítulos, se centra en la primera y últimas tareas consideradas.En el capítulo 1, se da una breve introducción y una visión general de lo que es el entrelazamiento (entanglement), empezando por el famoso artículo de Einstein, Podolosky y Rosen, y continuando con la formulación de John Bell de las llamados desigualdades de Bell. Definimos aquí conceptos generales acerca de los estados cuánticos enrelazados e introducimos algunas medidas de entrelazamiento importantes, que se utilizan posteriormente a lo largo de toda la tesis. En este capítulo, algunas fuentes de partículas entrelazadas (fotones) se mencionan brevemente. La importancia se pone en fuentes basadas en el proceso no lineal de generación paramétrica espontánea (SPDC, Spontaneous Parametric Down Conversion). La última parte de este capítulo está dedicado a mencionar algunas aplicaciones que se benefician de la utilización de estados entrelazados.El capítulo 2 se dedica al estudio sistemático de la generación de pares de fotones entrelazados, o no, en guías semiconductores de tipo Bragg. En primer lugar, se presenta una fuente de pares de fotones espectralmente no correlacionados, lo que se puede conseguir utilizando la geometría adecuada y la adecuada dispersión del material, a través del diseño estructural de las guías de onda. En segundo lugar, las guías de onda de Bragg se diseñan de manera que dan como resultado la generación de pares de fotones entrelazados en el grado de libertad de polarización con un ancho de banda grande. Finalmente, se presentan resultados experimentales de pares de fotones generados en este tipo de estructuras.En el capítulo 3, se explora la viabilidad de la generación de pares de fotones entrelazados en el grado espacial de libertad, es decir, en el momento angular orbital (OAM). En primer lugar, se investiga cómo crear un espacio de Hilbert altamente multidimensional utilizando modos OAM Para ello se ahce uso de materiales no lineales con chirped-qausi-phase-matching. Aquí mostramos cómo un aumento del chirp puede aumentar efectivamente el número de Schmidt en varios órdenes de magnitud. En segundo lugar, se investiga como fibras de vidrio con un núcleo en forma de anillo son capaces de generar y propagar los modos con OAM más simples.El Capítulo 4 se dedica a la localización Anderson y a los llamados paseos aleatorios cuánticos (Quantum random walks). En primer lugar se presenta una propuesta experimetnal para la realización de un paseo aleatorio discreto cuántico utilizando un interferómetro MAch-Zehnder con un modulador espacial de luz, que nos permite introducir diferentes tipos de ruido con diferentes tipos de estadística. En segundo lugar, se muestra cómo la localización transveral Anderson de luz parcialmente coherente se puede estudiar haciendo uso de pares de fotones entrelazado.

    Non-classical correlations, usually referred as entanglement, are ones of the most studied and discussed features of Quantum Mechanics, since the initial introduction of the concept in the decade of 1930s. Even nowadays, a lot of efforts, both theoretical and experimental, are devoted in this topic, that covers many distinct areas of physics, such as a quantum computing, quantum measurement, quantum communications, solid state physics, chemistry and even biology. The fundamental tasks that one should consider related to the entanglement are: -How to create quantum entangled states. -How to maintain entanglement during propagation against sources of decoherence. -How to effectively detect it. -How to employ the benefits that entanglement offers. This thesis, divided into four chapters, concentrates on the first and last tasks considered above. In Chapter 1, a brief introduction and overview of what it is entanglement is given, starting with the famous paper of Einstein, Podolsky and Rosen, and continuing with John Bell's formulation of the so-called Bell's inequalities. We define here general concepts about entangled quantum states and introduce important entanglement measures, that are later used all over the thesis. In this chapter, sources of entangled particles (namely photons) are also mentioned. The importance is put on sources based on the nonlinear process of spontaneous parametric down-conversion. The last part of this chapter is then dedicated to a list of applications that benefit from the use of engangled states. Chapter 2 is devoted to the systematic study of the generation of entangled and non-entangled photon pairs in semiconductor Bragg reflection waveguides. Firstly, we present a source of photon pairs with a spectrally uncorrelated two-photon amplitude, achieved by a proper tailoring of the geometrical and material dispersions via structural design of waveguides. Secondly, Bragg reflection waveguides are designed in a scuh way, that results in the generation of spectrally broadband paired photons entangled in the polarization degree of freedom. Finally, we present experimental results of entangled photon pairs generation in this type of structures. In Chapter 3, we explore the feasibility of the generation of photon pairs entangled in the spatial degree of freedom, i.e. in the orbital angular momentum (OAM). Firstly, we examine how to create a highly multidimensional Hilbert space using OAM modes obtained in a chipred-poled nonlinear bulk crystals. Here, we show, how an increase of the chirp of the poling can effectively increase the Schmidt number by several orders of magnitude. Secondly, we investigate periodically poled silica glass fibres with a ring-shpaed core, that are capable to support the generation of simple OAM modes. The final Chapter 4 is dedicated to the Anderson localization and quantum random walks. At the beginning of this chapter, we present an experimental proposal for the realization of a discrete quantum random walks using the multi-path Mach-Zehnder interferometer with a spatial light modulator, that allows us to introduce different types of statistical or dynamical disorders. And secondly, we show how the transverse Anderson localization of partially coherent light, with a variable first-order degree of coherence, can be studied making use of entangled photon pairs.

    Las correlaciones cuánticas, normalmente conocidas como entanglement, son uno de los temas más estudiados y discutidos de la Mecánica Cuántica, desde la introducción del concepto en la década de 1930. Incluso hoy en día, una gran cantidad de esfuerzos, tanto teóricos como experimentales, se dedican en este tema, que cubre muchas áreas distintas de la física, tales como medición cuántica (quantum metrology), computación cuántica (quantum computing), comunicaciones cuánticas (quantum communications), física de estado sólido, química e incluso biología. Las tareas fundamentales de investigación que uno debe considerar en relación con entrelazamiento son: -Cómo crear estados cuánticos entangled. -Cómo mantener el entanglement durante la propagación, en contra de las fuentes que pueden crear de-coherencia. -Cómo emplear los beneficios que el entanglement ofrece. Esta tesis, dividida en cuatro capítulos, se centra en la primera y últimas tareas consideradas. En el capítulo 1, se da una breve introducción y una visión general de lo que es el entrelazamiento (entanglement), empezando por el famoso artículo de Einstein, Podolosky y Rosen, y continuando con la formulación de John Bell de las llamados desigualdades de Bell. Definimos aquí conceptos generales acerca de los estados cuánticos enrelazados e introducimos algunas medidas de entrelazamiento importantes, que se utilizan posteriormente a lo largo de toda la tesis. En este capítulo, algunas fuentes de partículas entrelazadas (fotones) se mencionan brevemente. La importancia se pone en fuentes basadas en el proceso no lineal de generación paramétrica espontánea (SPDC, Spontaneous Parametric Down Conversion). La última parte de este capítulo está dedicado a mencionar algunas aplicaciones que se benefician de la utilización de estados entrelazados. El capítulo 2 se dedica al estudio sistemático de la generación de pares de fotones entrelazados, o no, en guías semiconductores de tipo Bragg. En primer lugar, se presenta una fuente de pares de fotones espectralmente no correlacionados, lo que se puede conseguir utilizando la geometría adecuada y la adecuada dispersión del material, a través del diseño estructural de las guías de onda. En segundo lugar, las guías de onda de Bragg se diseñan de manera que dan como resultado la generación de pares de fotones entrelazados en el grado de libertad de polarización con un ancho de banda grande. Finalmente, se presentan resultados experimentales de pares de fotones generados en este tipo de estructuras. En el capítulo 3, se explora la viabilidad de la generación de pares de fotones entrelazados en el grado espacial de libertad, es decir, en el momento angular orbital (OAM). En primer lugar, se investiga cómo crear un espacio de Hilbert altamente multidimensional utilizando modos OAM Para ello se ahce uso de materiales no lineales con chirped-qausi-phase-matching. Aquí mostramos cómo un aumento del chirp puede aumentar efectivamente el número de Schmidt en varios órdenes de magnitud. En segundo lugar, se investiga como fibras de vidrio con un núcleo en forma de anillo son capaces de generar y propagar los modos con OAM más simples. El Capítulo 4 se dedica a la localización Anderson y a los llamados paseos aleatorios cuánticos (Quantum random walks). En primer lugar se presenta una propuesta experimetnal para la realización de un paseo aleatorio discreto cuántico utilizando un interferómetro MAch-Zehnder con un modulador espacial de luz, que nos permite introducir diferentes tipos de ruido con diferentes tipos de estadística. En segundo lugar, se muestra cómo la localización transveral Anderson de luz parcialmente coherente se puede estudiar haciendo uso de pares de fotones entrelazado

  • Quantum-based spectroscopy and efficient energy transport with biomolecules  Open access

     León Montiel, Roberto De Jesús
    Universitat Politècnica de Catalunya
    Theses

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    Por muchos años, los campos de la óptica cuántica y la biología raramente han compartido un mismo camino. En la óptica cuántica, la mayoría de los conceptos y técnicas desarrolladas a lo largo de los años son válidas sólo en sistemas donde un número pequeño de grados de libertad es considerado y, más importante aún, donde se asume que los sistemas bajo estudio están completamente aislados del medio ambiente que los rodea. Esta situación está muy lejos de lo que podemos encontrar en la naturaleza. Los complejos biológicos son, por definición, sistemas a altas temperaturas, sujetos a fluctuaciones, en los cuales se cree que los fenómenos cuánticos son imposibles de observar. Sin embargo, en años recientes, esta creencia ha sido cuestionada por diferentes trabajos en los que conceptos de mecánica cuántica han sido usados con el objetivo de describir la dinámica de procesos biológicos de gran importancia como, por ejemplo, el transporte de energía en los complejos de captación de luz en sistemas fotosintéticos. El objetivo de esta tesis se divide en dos. Primeramente, investigaremos cómo las ideas y técnicas usadas comunmente en óptica cuántica pueden ser explotadas con el objetivo de desarrollar nuevas técnicas de espectroscopía y, segundo, estudiaremos hasta que punto los fenómenos cuánticos microscópicos pueden influir en el comportamiento del transporte eficiente de energía en sistemas fotosintéticos de captación de luz. Este problema es particularmente relevante, pues el entender los mecanismos fundamentales que permiten un eficiente transporte de energía en sistemas fotosintéticos nos podría conducir al diseño de nuevas tecnologías de captación y recolección de energía como, por ejemplo, celdas solares orgánicas de alta eficiencia.

    For many years, the fields of quantum optics and biology have rarely shared a common path. In quantum optics, most of the concepts and techniques developed over the years stand for systems where only a few degrees of freedom are considered and, more importantly, where the systems under study are assumed to be completely isolated from their surrounding environment. This situation is far from what we can find in nature. Biological complexes are, by definition, warm, wet and noisy systems subjected to environmental fluctuations, where quantum phenomena are unlikely to be observed. Notwithstanding, in recent years, this paradigm has begun to be questioned by several works where quantum-mechanical concepts have been introduced in order to describe the dynamics of important biological processes, such as energy transport in photosynthetic light-harvesting complexes. The goal of this thesis is twofold. Firstly, we will investigate how ideas and techniques routinely used in quantum optics can be exploited in order to develop new quantum-based spectroscopy techniques and, secondly, we will examine to what extent microscopic quantum phenomena could impact on the efficient transport behavior of photosynthetic light-havesting complexes. This problem is particularly relevant, because the understanding of the fundamental mechanisms that enable the highly efficient transport of energy in photosynthetic systems could lead us to the design of future quantum-inspired light-harvesting technologies, such as high-efficiency organic solar cells.

    Por muchos años, los campos de la óptica cuántica y la biología raramente han compartido un mismo camino. En la óptica cuántica, la mayoría de los conceptos y técnicas desarrolladas a lo largo de los años son válidas sólo en sistemas donde un número pequeño de grados de libertad es considerado y, más importante aún, donde se asume que los sistemas bajo estudio están completamente aislados del medio ambiente que los rodea. Esta situación está muy lejos de lo que podemos encontrar en la naturaleza. Los complejos biológicos son, por definición, sistemas a altas temperaturas, sujetos a fluctuaciones, en los cuales se cree que los fenómenos cuánticos son imposibles de observar. Sin embargo, en años recientes, esta creencia ha sido cuestionada por diferentes trabajos en los que conceptos de mecánica cuántica han sido usados con el objetivo de describir la dinámica de procesos biológicos de gran importancia como, por ejemplo, el transporte de energía en los complejos de captación de luz en sistemas fotosintéticos. El objetivo de esta tesis se divide en dos. Primeramente, investigaremos cómo las ideas y técnicas usadas comunmente en óptica cuántica pueden ser explotadas con el objetivo de desarrollar nuevas técnicas de espectroscopía y, segundo, estudiaremos hasta que punto los fenómenos cuánticos microscópicos pueden influir en el comportamiento del transporte eficiente de energía en sistemas fotosintéticos de captación de luz. Este problema es particularmente relevante, pues el entender los mecanismos fundamentales que permiten un eficiente transporte de energía en sistemas fotosintéticos nos podría conducir al diseño de nuevas tecnologías de captación y recolección de energía como, por ejemplo, celdas solares orgánicas de alta eficiencia.

  • Efficient heralding of polarization-entangled photons from type-0 and type-II spontaneous parametric downconversion in periodically poled KTiOPO 4

     Steinlechner, Fabian; Gilaberte, Marta; Jofre, Marc; Scheidl, Thomas; Perez Torres, Juan; Pruneri, Valerio; Ursin, Rupert
    Journal of the Optical Society of America B. Optical physics
    Vol. 31, num. 9, p. 2068-2076
    DOI: 10.1364/JOSAB.31.002068
    Date of publication: 2014-09-01
    Journal article

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    Ultrabright sources of entangled photon pairs with high heralding efficiency are an important step in the pursuit of high-bit-rate entanglement-base quantum key distribution, as well as an enabling tool for loss-sensitive quantum optics experiments. Here, we present a robust single-mode fiber-coupled source of polarization-entangled photons around 810 nm with both high brightness and heralding efficiency. Our approach is based on quasi-phase-matched spontaneous parametric downconversion (SPDC) from periodically poled KTiOPO4 in a Sagnac loop configuration. We demonstrate a high degree of two-photon polarization entanglement for single-frequency-pumped type-0 and type-II SPDC, and conduct a conclusive comparison in terms of efficiency and spectral characteristics. In light of applications outside a laboratory environment, we evaluate the feasibility of pumping nonlinear crystals with free-running laser diodes. © 2014 Optical Society of America.

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    Measuring the translational and rotational velocities of particles in helical motion using structured light  Open access

     Rosales Guzmán, Carmelo; Hermosa, Nathaniel; Belmonte Molina, Aniceto; Perez Torres, Juan
    The Virtual Journal for Biomedical Optics
    Vol. 9, num. 8, p. 16504-16509
    DOI: 10.1364/OE.22.016504
    Date of publication: 2014-08-07
    Journal article

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    We measure the rotational and translational velocity components of particles moving in helical motion under a Laguerre-Gaussian mode illumination. The moving particle reflects light that acquires an additional frequency shift proportional to the velocity of rotation in the transverse plane, on top of the usual frequency shift due to the longitudinal motion. We determined both the translational and rotational velocities of the particles by switching between two modes: by illuminating with a Gaussian beam, we can isolate the longitudinal frequency shift; and by using a Laguerre-Gaussian mode, the frequency shift due to the rotation can be determined. Our technique can be used to characterize the motility of microorganisms with a full three-dimensional movement.

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    Measuring the translational and rotational velocities of particles in helical motion using structured light  Open access

     Rosales Guzmán, Carmelo; Hermosa, Nathaniel; Belmonte Molina, Aniceto; Perez Torres, Juan
    Optics express
    Vol. 22, num. 13, p. 16504-16509
    DOI: 10.1364/OE.22.016504
    Date of publication: 2014-06-30
    Journal article

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    We measure the rotational and translational velocity components of particles moving in helical motion under a Laguerre-Gaussian mode illumination. The moving particle reflects light that acquires an additional frequency shift proportional to the velocity of rotation in the transverse plane, on top of the usual frequency shift due to the longitudinal motion. We determined both the translational and rotational velocities of the particles by switching between two modes: by illuminating with a Gaussian beam, we can isolate the longitudinal frequency shift; and by using a Laguerre-Gaussian mode, the frequency shift due to the rotation can be determined. Our technique can be used to characterize the motility of microorganisms with a full three-dimensional movement.

    We measure the rotational and translational velocity components of particles moving in helical motion under a Laguerre-Gaussian mode illumination. The moving particle reflects light that acquires an additional frequency shift proportional to the velocity of rotation in the transverse plane, on top of the usual frequency shift due to the longitudinal motion. We determined both the translational and rotational velocities of the particles by switching between two modes: by illuminating with a Gaussian beam, we can isolate the longitudinal frequency shift; and by using a Laguerre-Gaussian mode, the frequency shift due to the rotation can be determined. Our technique can be used to characterize the motility of microorganisms with a full three-dimensional movement. (C) 2014 Optical Society of America

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    Measurement-based tailoring of Anderson localization of partially coherent light  Open access

     Svozilik, Jiri; Perina, Jan; Perez Torres, Juan
    Physical review. A, general physics
    Vol. 83, p. 053808-1-053808-6
    DOI: 10.1103/PhysRevA.89.053808
    Date of publication: 2014-05-08
    Journal article

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    We put forward an experimental configuration to observe transverse Anderson localization of partially coherent light beams with a tunable degree of first-order coherence. The scheme makes use of entangled photons propagating in disordered waveguide arrays and is based on the unique relationship between the degree of entanglement of a pair of photons and the coherence properties of the individual photons constituting the pair. The scheme can be readily implemented with current waveguide-on-a-chip technology, and surprisingly the tunability of the coherence properties of the individual photons is done at the measurement stage, without resorting to changes of the light source itself.

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    Limitations to the determination of a Laguerre¿Gauss spectrum via projective, phase-flattening measurement  Open access

     Qassim, Hammam; Miatto, Filippo M.; Perez Torres, Juan; Padgett, Miles J.; Karimi, Ebrahim; Boyd, Robert W.
    Journal of the Optical Society of America B. Optical physics
    Vol. 31, num. 6, p. A20-A21
    DOI: 10.1364/JOSAB.31.000A20
    Date of publication: 2014-04-07
    Journal article

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    One of the most widely used techniques for measuring the orbital angular momentum (OAM) components of a light beam is to flatten the spiral phase front of a mode, in order to couple it to a single-mode optical fiber (SMOF). This method, however, suffers from an efficiency that depends on the OAM of the initial mode and on the presence of higher-order radial modes. The reason is that once the phase has been flattened, the field retains its ringed intensity pattern and is therefore a nontrivial superposition of purely radial modes, of which only the fundamental one couples to a SMOF. In this paper, we study the efficiency of this technique both theoretically and experimentally. We find that even for low values of the OAM, a large amount of light can fall outside the fundamental mode of the fiber, and we quantify the losses as functions of the waist of the coupling beam of the OAM and radial indices. Our results can be used as a tool to remove the efficiency bias where fair-sampling loopholes are not a concern. However, we hope that our study will encourage the development of better detection methods of the OAM content of a beam of light.

  • Hyperentangled photon sources in semiconductor waveguides

     Kang, D.; Helt, L. G.; Zhukovsky, Sergei V.; Perez Torres, Juan; Sipe, J. E.; Helmy, A.S.
    Physical review A
    Vol. 89, num. 2, p. 023833-1-023833-8
    DOI: 10.1103/PhysRevA.89.023833
    Date of publication: 2014-02-19
    Journal article

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    We propose and analyze the performance of a technique to generate mode and polarization hyperentangled photons in monolithic semiconductor waveguides using two concurrent type-II spontaneous parametric down-conversion (SPDC) processes. These two SPDC processes are achieved by waveguide engineering which allows for simultaneous modal phase matching with the pump beam in a higher-order mode. Paired photons generated in each process are cross polarized and guided by different guiding mechanisms, which produces entanglement in both polarization and spatial mode. Theoretical analysis shows that the output quantum state has a high quality of hyperentanglement by spectral filtering with a bandwidth of a few nanometers, while off-chip compensation is not needed. This technique offers a path to realize an electrically pumped hyperentangled photon source.

  • Measurement of sub-pulse-width temporal delays via spectral interference induced by weak value amplification

     Salazar Serrano, Luis Jose; Janner, Davide; Brunner, Nicolas; Pruneri, Valerio; Perez Torres, Juan
    Physical review A
    Vol. 89, num. 1, p. 012126-1-012126-5
    DOI: 10.1103/PhysRevA.89.012126
    Date of publication: 2014-01-27
    Journal article

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    We demonstrate experimentally a scheme to measure small temporal delays, much smaller than the pulse width, between optical pulses. Specifically, we observe an interference effect, based on the concepts of quantum weak measurements and weak value amplification, through which a sub-pulse-width temporal delay between two femtosecond pulses induces ameasurable shift of the central frequency of the pulse. The amount of frequency shift, and the accompanying losses of the measurement, can be tailored by postselecting different states of polarization. Our scheme requires only spectrum measurements and linear optics elements, hence greatly facilitating its implementation. Thus it appears to be a promising technique for measuring small and rapidly varying temporal delays.

  • Nanostep height measurement via spatial mode projection

     Hermosa, Nathaniel; Rosales Guzmán, Carmelo; Pereira, Silvania F.; Perez Torres, Juan
    Optics letters
    Vol. 39, num. 2, p. 299-302
    DOI: 10.1364/OL.39.000299
    Date of publication: 2014-01-15
    Journal article

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    We demonstrate an optical scheme for measuring the thickness of thin nanolayers with the use of light beam¿s spatial modes. The novelty in our scheme is the projection of the beam reflected by the sample onto a properly tailored spatial mode. In the experiment described below, we are able to measure a step height smaller than 10 nm, i.e., one-eightieth (1/80) of the wavelength with a standard error in the picometer scale. Since our scheme enhances the signal-to-noise ratio, which effectively increases the sensitivity of detection, the extension of this technique to the detection of subnanometric layer thicknesses is feasible.

  • Steering and guiding light with light in a nanosuspension

     Terborg, Roland A.; Perez Torres, Juan; Volke-Sepulveda, Karen
    Optics letters
    Vol. 38, num. 24, p. 5284-5287
    DOI: 10.1364/OL.38.005284
    Date of publication: 2013-12-15
    Journal article

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    We experimentally demonstrate guiding of a low-power probe beam (633 nm wavelength) by means of a light-induced waveguide generated by the self-focusing of a strong pump beam (532 nm wavelength) in an artificial nonlinear medium, constituted by a colloidal suspension of dielectric nanoparticles. We also demonstrate optical steering of the probe beam by controlling the direction of propagation of the pump beam. The distance over which guiding is demonstrated (5 mm) is remarkably long when compared with previous experiments.

  • Experimental detection of transverse particle movement with structured light

     Rosales Guzmán, Carmelo; Hermosa, Nathaniel; Belmonte Molina, Aniceto; Perez Torres, Juan
    Scientific reports
    Vol. 3, p. 1-5
    DOI: 10.1038/srep02815
    Date of publication: 2013-10-02
    Journal article

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    One procedure widely used to detect the velocity of a moving object is by using the Doppler effect. This is the perceived change in frequency of a wave caused by the relative motion between the emitter and the detector, or between the detector and a reflecting target. The relative movement, in turn, generates a time-varying phase which translates into the detected frequency shift. The classical longitudinal Doppler effect is sensitive only to the velocity of the target along the line-of-sight between the emitter and the detector (longitudinal velocity), since any transverse velocity generates no frequency shift. This makes the transverse velocity undetectable in the classical scheme. Although there exists a relativistic transverse Doppler effect, it gives values that are too small for the typical velocities involved in most laser remote sensing applications. Here we experimentally demonstrate a novel way to detect transverse velocities. The key concept is the use of structured light beams. These beams are unique in the sense that their phases can be engineered such that each point in its transverse plane has an associated phase value. When a particle moves across the beam, the reflected light will carry information about the particle¿s movement through the variation of the phase of the light that reaches the detector, producing a frequency shift associated with the movement of the particle in the transverse plane.

  • Puentes, Hermosa, and Torres reply

     Puentes, Graciana; Hermosa, Nathaniel; Perez Torres, Juan
    Physical review letters
    Vol. 111, num. 2, p. 028902-1
    DOI: 10.1103/PhysRevLett.111.028902
    Date of publication: 2013-07-10
    Journal article

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    Reply to comment on ``Weak measurements with orbital- Angular-Momentum Pointer States¿¿ by Puentes, Hermosa, and Torres

  • Transverse Doppler effect using engineered optical beams

     Rosales Guzmán, Carmelo; Hermosa, Nathaniel; Belmonte Molina, Aniceto; Perez Torres, Juan
    Coherent Laser Radar Conference
    p. 1-3
    Presentation's date: 2013-06-17
    Presentation of work at congresses

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    When a light beam with a transverse spatially-varying phase is considered for optical remote sensing, in addition to the usual longitudinal Doppler frequency shift of the returned signal induced by the motion of the scatter along the beam axis, a new transversal Doppler shift appears which is due to the motion of the scatterer in the plane perpendicular to the beam axis [1]. With engineered light, light scattered by a particle at a particular location is associated with a specific value of the phase of the incident field at that point. As the particle move across the beam, it produces an echo that is dependent on the phase of the incident field. By noting the change of the phase of the echo (Doppler Effect), the movement can be measured. We discuss here how this new effect can be used to enhance the current capabilities of optical remote sensing systems, adding the capacity to detect more complex movements of scatters.

  • Generation of polarization-entangled photon pairs in a Bragg reflection waveguide

     Valles Marin, Adam; Hendrych, M.; Svozilik, Jiri; Machulka, R.; Abolghasem, P.; Kang, D.; Bijlani, B.J.; Helmy, A.S.; Perez Torres, Juan
    Optics express
    Vol. 21, num. 9, p. 10841-10849
    DOI: 10.1364/OE.21.010841
    Date of publication: 2013-06
    Journal article

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    We demonstrate experimentally that spontaneous parametric down-conversion in an AlxGa1-xAs semiconductor Bragg reflection waveguide can make for paired photons highly entangled in the polarization degree of freedom at the telecommunication wavelength of 1550 nm. The pairs of photons show visibility higher than 90% in several polarization bases and violate a Clauser-Horne-Shimony-Holt Bell-like inequality by more than 3 standard deviations. This represents a significant step toward the realization of efficient and versatile self pumped sources of entangled photon pairs on-chip.

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    Highly efficient noise-assisted energy transport in classical oscillator systems  Open access

     Leon Montiel, R de J.; Perez Torres, Juan
    Physical review letters
    Vol. 110, num. 21, p. 1-4
    DOI: 10.1103/PhysRevLett.110.218101
    Date of publication: 2013-05
    Journal article

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    Photosynthesis is a biological process that involves the highly efficient transport of energy captured from the Sun to a reaction center, where conversion into useful biochemical energy takes place. Using a quantum description, Rebentrost et al. [ New J. Phys. 11 033003 (2009)] and Plenio and Huelga [ New J. Phys. 10 113019 (2008)] have explained this high efficiency as the result of the interplay between the quantum coherent evolution of the photosynthetic system and noise introduced by its surrounding environment. Even though one can always use a quantum perspective to describe any physical process, since everything follows the laws of quantum mechanics, is the use of quantum theory imperative to explain this high efficiency? Recently, it has been shown by Eisfeld and Briggs [ Phys. Rev. E 85 046118 (2012)] that a purely classical model can be used to explain main aspects of the energy transfer in photosynthetic systems. Using this approach, we demonstrate explicitly here that highly efficient noise-assisted energy transport can be found as well in purely classical systems. The wider scope of applicability of the enhancement of energy transfer assisted by noise might open new ways for developing new technologies aimed at enhancing the efficiency of a myriad of energy transfer systems, from information channels in microelectronic circuits to long-distance high-voltage electrical lines.

    Photosynthesis is a biological process that involves the highly-efficient transport of energy captured from the sun to a reaction center, where conversion into useful biochemical energy takes place. Even though one can always use a quantum perspective to describe any physical process, since everything follows the laws of Quantum Mechanics, is the use of quantum theory imperative to explain this high efficiency? Making use of the quantum-classical correspondence of electronic energy transfer recently introduced by Eisfeld and Briggs [Phys. Rev. E 85, 046118 (2012)], we show here that the highly-efficient noise-assisted energy transport described by Rebentrost et al. [New J. Phys. 11, 033003 (2009)], and Plenio and Huelga [New J. Phys. 10, 113019 (2008)], as the result of the interplay between the quantum coherent evolution of the photosynthetic system and noise introduced by its surrounding environment, it can be found as well in purely classical systems. The wider scope of applicability of the enhancement of energy transfer assisted by noise might open new ways for developing new technologies aimed at enhancing the efficiency of a myriad of energy transfer systems, from information channels in micro-electronic circuits to long-distance high-voltage electrical lines.

  • Phase-stable source of polarization-entangled photons in a linear double-pass configuration

     Steinlechner, Fabian; Ramelow, Sven; Jofre, Marc; Gilaberte, Marta; Jennewein, Thomas; Perez Torres, Juan; Mitchell, Morgan W.; Pruneri, Valerio
    Optics express
    Vol. 21, num. 10, p. 11943-11951
    DOI: 10.1364/OE.21.011943
    Date of publication: 2013-05
    Journal article

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    We demonstrate a compact, robust, and highly efficient source of polarization-entangled photons, based on linear bi-directional down-conversion in a novel 'folded sandwich' configuration. Bi-directionally pumping a single periodically poled KTiOPO4 (ppKTP) crystal with a 405-nm laser diode, we generate entangled photon pairs at the nondegenerate wavelengths 784 nm (signal) and 839 nm (idler), and achieve an unprecedented detection rate of 11.8 kcps for 10.4 mu W of pump power (1.1 million pairs / mW), in a 2.9-nm bandwidth, while maintaining a very high two-photon entanglement quality, with a Bell-state fidelity of 99.3 +/- 0.3%.

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    Role of the spectral shape of quantum correlations in two-photon virtual-state spectroscopy  Open access

     Leon Montiel, R de J.; Svozilik, Jiri; Salazar Serrano, Luis Jose; Perez Torres, Juan
    New journal of physics
    Vol. 15
    DOI: 10.1088/1367-2630/15/5/053023
    Date of publication: 2013-05
    Journal article

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    The true role of entanglement in two-photon virtual-state spectroscopy (Saleh et al 1998 Phys. Rev. Lett. 80 3483), a two-photon absorption spectroscopic technique that can retrieve information about the energy level structure of an atom or a molecule, is controversial. The consideration of closely related techniques, such as multidimensional pump¿probe spectroscopy (Roslyak et al 2009 Phys. Rev. A 79, 063409), suggests that spectroscopic information might also be retrieved by using uncorrelated pairs of photons. Here we show that this is not the case. In the two-photon absorption process, the ability to obtain information about the energy level structure of a medium depends on the spectral shape of existing temporal (frequency) correlations between the absorbed photons. In fact, it is a combination of both the presence of frequency correlations (entanglement) and their specific spectral shape that makes the realization of two-photon virtual-state spectroscopy possible. This result helps in selecting the type of two-photon source that needs to be used in order to experimentally perform the two-photon virtual-state spectroscopy technique.

    The true role of entanglement in two-photon virtual-state spectroscopy (Saleh et al 1998 Phys. Rev. Lett. 80 3483), a two-photon absorption spectroscopic technique that can retrieve information about the energy level structure of an atom or a molecule, is controversial. The consideration of closely related techniques, such as multidimensional pump–probe spectroscopy (Roslyak et al 2009 Phys. Rev. A 79, 063409), suggests that spectroscopic information might also be retrieved by using uncorrelated pairs of photons. Here we show that this is not the case. In the two-photon absorption process, the ability to obtain information about the energy level structure of a medium depends on the spectral shape of existing temporal (frequency) correlations between the absorbed photons. In fact, it is a combination of both the presence of frequency correlations (entanglement) and their specific spectral shape that makes the realization of two-photon virtual-state spectroscopy possible. This result helps in selecting the type of two-photon source that needs to be used in order to experimentally perform the two-photon virtual-state spectroscopy technique.

  • Ultra-bright source of polarization-entangled photons in a linear double-pass configuration

     Steinlechner, Fabian; Ramelow, Sven; Jofre, Marc; Gilaberte, Marta; Jennewein, Thomas; Perez Torres, Juan; Mitchell, Morgan W.; Pruneri, Valerio
    European Conference on Lasers and Electro-Optics - International Quantum Electronics Conference
    DOI: 10.1109/CLEOE-IQEC.2013.6801674
    Presentation's date: 2013-05
    Presentation of work at congresses

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    A number of key experiments in free-space have shown that polarization-entangled photons are not only of paramount importance to fundamental quantum optics, but can also find real-world applications in space, such as quantum enhanced metrological schemes, quantum communication and quantum cryptography. A crucial requirement for envisaged satellite-link experiments is the development of efficient space-qualified sources of entangled photons.

  • Digital coherent receiver for orbital angular momentum demultiplexing

     Belmonte Molina, Aniceto; Perez Torres, Juan
    Optics letters
    Vol. 38, num. 2, p. 241-243
    DOI: OL.38.000241
    Date of publication: 2013-01-15
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    Helico-conical optical beams self-heal  Open access

     Hermosa, Nathaniel; Rosales Guzmán, Carmerlo; Perez Torres, Juan
    Optics letters
    Vol. 38, num. 3, p. 383-385
    DOI: 10.1364/OL.38.000383
    Date of publication: 2013-01
    Journal article

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    An optical beam is said to be self-healing when, distorted by an obstacle, the beam corrects itself upon propagation. In this Letter we show, through experiments supported by numerical simulations, that Helico-conical optical beams self-heal. We observe the strong resilience of these beams with different types of obstructions, and relate this to the characteristics of their transverse energy flow.

    An optical beam is said to be self-healing when, distorted by an obstacle, the beam corrects itself upon propagation. In this Letter we show, through experiments supported by numerical simulations, that Helico-conical optical beams self-heal. We observe the strong resilience of these beams with different types of obstructions, and relate this to the characteristics of their transverse energy fl

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    Shaping the ultrafast temporal correlations of thermal-like photons  Open access

     Torres Company, Victor; Perez Torres, Juan; Friberg, Ari T.
    Physical review letters
    Vol. 109, num. 24, p. 1-5
    DOI: 10.1103/PhysRevLett.109.243905
    Date of publication: 2012-12-14
    Journal article

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    We show that the temporal correlations between two light beams arising from a broadband thermal-like source can be controlled in the femtosecond regime. Specifically, by introducing spectral phase-only masks in the path of one of the beams, we show that the timing and strength of the photon correlations can be programmed on demand. This example demonstrates that the interbeam second-order coherence function propagates as a phase-sensitive ultrafast wave packet in the path towards the detectors, and is thus, susceptible to be modified by acting on just one of the beams. For quite some time, it has been thought that this could only happen with sources showing time-energy entanglement. Our work shows that such a property is due to the existence of a certain type of correlation, but not necessarily the entanglement.

    We show that the temporal correlations between two light beams arising from a broadband thermal-like source can be controlled in the femtosecond regime. Specifically, by introducing spectral phase-only masks in the path of one of the beams, we show that the timing and strength of the photon correlations can be programmed on demand. This example demonstrates that the interbeam second-order coherence function propagates as a phase-sensitive ultrafast wave packet in the path towards the detectors, and is thus, susceptible to be modified by acting on just one of the beams. For quite some time, it has been thought that this could only happen with sources showing time-energy entanglement. Our work shows that such a property is due to the existence of a certain type of correlation, but not necessarily the entanglement

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    Implementation of a spatial two-dimensional quantum random walk with tunable decoherence  Open access

     Svozilik, Jiri; León Montiel, R.D.J.; Perez Torres, Juan
    Physical review A
    Vol. 86, num. 5, p. 1-6
    DOI: 10.1103/PhysRevA.86.052327
    Date of publication: 2012-11
    Journal article

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    We put forward a versatile and highly scalable experimental setup for the realization of discrete two-dimensional quantum random walks with a single-qubit coin and tunable degree of decoherence. The proposed scheme makes use of a small number of simple optical components arranged in a multipath Mach-Zehnder-like configuration, where a weak coherent state is injected. Environmental effects (decoherence) are generated by a spatial light modulator, which introduces pure dephasing in the transverse spatial plane perpendicular to the direction of propagation of the light beam. By controlling the characteristics of this dephasing, one can explore a great variety of scenarios of quantum random walks: pure quantum evolution (ballistic spread), fast fluctuating environment leading to a diffusive classical random walk, and static disorder resulting in the observation of Anderson localization.

    We put forward a versatile and highly scalable experimental setup for the realization of discrete two-dimensional quantum random walks with a single-qubit coin and tunable degree of decoherence. The proposed scheme makes use of a small number of simple optical components arranged in a multipath Mach-Zehnder-like configuration, where a weak coherent state is injected. Environmental effects (decoherence) are generated by a spatial light modulator, which introduces pure dephasing in the transverse spatial plane perpendicular to the direction of propagation of the light beam. By controlling the characteristics of this dephasing, one can explore a great variety of scenarios of quantum random walks: pure quantum evolution (ballistic spread), fast fluctuating environment leading to a diffusive classical random walk, and static disorder resulting in the observation of Anderson localization

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    High spatial entanglement via chirped quasi-phase-matched optical parametric down-conversion  Open access

     Svozilik, Jiri; Perina, Jr., Jan; Perez Torres, Juan
    Physical review A
    Vol. 86, p. 1-5
    DOI: 10.1103/PhysRevA.86.052318
    Date of publication: 2012-11
    Journal article

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    By making use of the spatial shape of paired photons, parametric down-conversion allows the generation of two-photon entanglement in a multidimensional Hilbert space. How much entanglement can be generated in this way? In principle, the infinite-dimensional nature of the spatial degree of freedom renders unbounded the amount of entanglement available. However, in practice, the specific configuration used, namely, its geometry, the length of the nonlinear crystal, and the size of the pump beam, can severely limit the value that could be achieved. Here we show that the use of quasi-phase-matching engineering allows one to increase the amount of entanglement generated, reaching values of tens of ebits of entropy of entanglement under different conditions. Our work thus opens a way to fulfill the promise of generating massive spatial entanglement under a diverse variety of circumstances, some more favorable for its experimental implementation

    By making use of the spatial shape of paired photons, parametric down-conversion allows the generation of two-photon entanglement in a multidimensional Hilbert space. How much entanglement can be generated in this way? In principle, the infinite-dimensional nature of the spatial degree of freedom renders unbounded the amount of entanglement available. However, in practice, the specific configuration used, namely, its geometry, the length of the nonlinear crystal, and the size of the pump beam, can severely limit the value that could be achieved. Here we show that the use of quasi-phase-matching engineering allows one to increase the amount of entanglement generated, reaching values of tens of ebits of entropy of entanglement under different conditions. Our work thus opens a way to fulfill the promise of generating massive spatial entanglement under a diverse variety of circumstances, some more favorable for its experimental implementation.

  • Light with enhanced optical chirality

     Rosales Guzmán, Carmerlo; Volke Sepulveda, K.; Perez Torres, Juan
    Optics letters
    Vol. 37, num. 17, p. 3486-3488
    DOI: 10.1364/OL.37.003486
    Date of publication: 2012-09-01
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  • Weak interference in the high-signal regime

     Perez Torres, Juan; Puentes, G.; Hermosa, Nathaniel; Salazar Serrano, Luis Jose
    Optics express
    Vol. 20, num. 17, p. 18869-18875
    DOI: 10.1364/OE.20.018869
    Date of publication: 2012-08-13
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  • Experimental estimation of the dimension of classical and quantum systems

     Hendrych, Martin; Gallego, Rodrigo; Micuda, M.; Brunner, Nicolas; Acín, Antonio; Perez Torres, Juan
    Nature physics
    Vol. 8, num. 8, p. 588-591
    DOI: 10.1038/nphys2334
    Date of publication: 2012-08
    Journal article

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    Weak measurements with orbital-angular-momentum pointer states  Open access

     Puentes, G.; Hermosa, Nathaniel; Perez Torres, Juan
    Physical review letters
    Vol. 109, num. 4, p. 040401-1-040401-5
    DOI: 10.1103/PhysRevLett.109.040401
    Date of publication: 2012-07-24
    Journal article

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    Weak measurements are a unique tool for accessing information about weakly interacting quantum systems with minimal back action. Joint weak measurements of single-particle operators with pointer states characterized by a two-dimensional Gaussian distribution can provide, in turn, key information about quantum correlations that can be relevant for quantum information applications. Here we demonstrate that by employing two-dimensional pointer states endowed with orbital angular momentum (OAM), it is possible to extract weak values of the higher order moments of single-particle operators, an inaccessible quantity with Gaussian pointer states only. We provide a specific example that illustrates the advantages of our method both in terms of signal enhancement and information retrieval.

    Weak measurements are a unique tool for accessing information about weakly interacting quantum systems with minimal back action. Joint weak measurements of single-particle operators with pointer states characterized by a two-dimensional Gaussian distribution can provide, in turn, key information about quantum correlations that can be relevant for quantum information applications. Here we demonstrate that by employing two-dimensional pointer states endowed with orbital angular momentum (OAM), it is possible to extract weak values of the higher order moments of single-particle operators, an inaccessible quantity with Gaussian pointer states only. We provide a specific example that illustrates the advantages of our method both in terms of signal enhancement and information retrieval.

  • Self-homodyne detection of the light orbital angular momentum

     Belmonte Molina, Aniceto; Perez Torres, Juan
    Optics letters
    Vol. 37, num. 14, p. 2940-2942
    DOI: 10.1364/OL.37.002940
    Date of publication: 2012-07-15
    Journal article

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  • Optical communications: Multiplexing twisted light

     Perez Torres, Juan
    Nature photonics
    Vol. 6, num. 7, p. 420-422
    DOI: 10.1038/nphoton.2012.154
    Date of publication: 2012-07
    Journal article

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  • Fast beam steering with full polarization control using a galvanometric optical scanner and polarization controller

     Jofre Cruanyes, Marc; Anzolin, G.; Steinlechner, Fabian; NESTOR HUGO, OLIVERIO; Perez Torres, Juan; Pruneri, Valerio; Mitchell, M. W.
    Optics express
    Vol. 20, num. 11, p. 12247-12260
    DOI: 10.1364/OE.20.012247
    Date of publication: 2012-05-21
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  • A high-brightness source of polarization-entangled photons optimized for applications in free space

     Steinlechner, Fabian; Trojek, P.; Jofre, Marc; Weier, H.; Pérez, Daniel; Jennewein, Thomas; Ursin, R.; Rarity, J.; Mitchell, M. W.; Perez Torres, Juan; Weinfurter, H.; Pruneri, Valerio
    Optics express
    Vol. 20, num. 3, p. 9640-9649
    DOI: 10.1364/OE.20.009640
    Date of publication: 2012-04-23
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  • Measurement of the temperature of atomic ensembles via which-way information

     León Montiel, R.D.J.; Perez Torres, Juan
    Physical review A
    Vol. 83, num. 3, p. 1-6
    DOI: 10.1103/PhysRevA.85.033801
    Date of publication: 2012-03-05
    Journal article

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    We unveil the relationship existing between the temperature of an ensemble of three-level atoms in a configuration, and the width of the emission cone of Stokes photons that are spontaneously emitted when atoms are excited by an optical pulse. This relationship, which is based on the amount of which-way information available about where the Stokes photon originated during the interaction, allows us to put forward a scheme to determine the temperature of atomic clouds by measuring the width of the emission cone. Unlike the commonly used time-of-flight measurements, with this technique, the atomic cloud is not destroyed during each measurement.

  • Enhancing the sensitivity and robustness of label-free imaging systems via stimulated Raman adiabatic passage

     León Montiel, R.D.J.; Perez Torres, Juan
    New journal of physics
    Vol. 14, num. 1, p. 1-12
    DOI: 10.1088/1367-2630/14/1/013018
    Date of publication: 2012-01
    Journal article

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    We show that the sensitivity and robustness of a label-free optical imaging technique based on stimulated Raman scattering (SRS) can be enhanced by using resonant optical transitions in a Raman adiabatic passage scheme. Our approach is based on the consideration that any enhancement of the flow of energy between two light beams involved in the SRS process is related to an increase in atomic population transfer between the energy levels of interest. One can thus profit from techniques developed in quantum optics to maximize such atomic population transfer for enhancing the sensitivity and robustness of optical imaging techniques.

  • Bragg reflection waveguide as a source of wavelength-multiplexed polarization-entangled photon pairs

     Svozilik, Jiri; Hendrych, Martin; Perez Torres, Juan
    Optics express
    Vol. 20, num. 14, p. 15015-15023
    DOI: 10.1364/OE.20.015015
    Date of publication: 2012
    Journal article

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  • Echo Doppler with structured light

     Belmonte Molina, Aniceto; Perez Torres, Juan
    Frontiers in Optics
    Presentation's date: 2012
    Presentation of work at congresses

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    When a light beam with a transverse spatially - varying phase is considered for optical remote sensing, in addition to the usual longitudinal Doppler freq uency shift of the returned signal induced by the motion of the scatter along the beam axis, a new transversal Doppler shift appears which is due to the motion of the scatterer in the plane perpendicular to the beam axis. We discuss here how this new effec t can be used to enhance the current capabilities of optical remote sensing systems, adding the capacity to detect more complex movements of scatters.

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    Optical Doppler shift with structured light  Open access

     Belmonte Molina, Aniceto; Perez Torres, Juan
    Optics letters
    Vol. 36, num. 22, p. 4437-4439
    DOI: 10.1364/OL.36.004437
    Date of publication: 2011-11-15
    Journal article

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    When a light beam with a transverse spatially varying phase is considered for optical remote sensing, in addition to the usual longitudinal Doppler frequency shift of the returned signal induced by the motion of the scatter along the beam axis, a new transversal Doppler shift appears associated to the motion of the scatterer in the plane perpendicular to the beam axis. We discuss here how this new effect can be used to enhance the current capabilities of optical measurement systems, adding the capacity to detect more complex movements of scatters

  • Flux enhancement of photons entangled in orbital angular momentum

     Palacios, Silvana; León Montiel, R.D.J.; Hendrych, Martin; Valencia, Alejandra; Perez Torres, Juan
    Optics express
    Vol. 19, num. 15, p. 14108-14120
    DOI: 10.1364/OE.19.014108
    Date of publication: 2011-07-18
    Journal article

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    Entangled photons are generally collected by detection systems that select their certain spatial modes, for example using single-mode optical fibers. We derive simple and easy-to-use expressions that allow us to maximize the coupling efficiency of entangled photons with specific orbital angular momentum (OAM) correlations generated by means of spontaneous parametric downconversion. Two different configurations are considered: one in which the beams with OAM are generated by conversion from beams without OAM, and the second when beams with OAM are generated directly from the nonlinear medium. Also, an example of how to generate a maximally entangled qutrit is presented.

  • Cancelation of dispersion and temporal modulation with non-entangled frequency-correlated photons

     Torres Company, Victor; Valencia, Alejandra; Hendrych, Martin; Perez Torres, Juan
    Physical review A
    Vol. 83, num. 2, p. 1-6
    DOI: 10.1103/PhysRevA.83.023824
    Date of publication: 2011-02-25
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  • Generation of paired photons in a quantum separable state in Bragg reflection waveguides

     Svozilik, Jiri; Hendrych, Martin; Helmy, Amr S.; Perez Torres, Juan
    Optics express
    Vol. 19, num. 4, p. 3115-3123
    DOI: 10.1364/OE.19.003115
    Date of publication: 2011-02-14
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  • Engineering nonlinear optic sources of photonic entanglement

     Perez Torres, Juan; Banaszek, K.; Walmsley, I.A.
    Progress in optics
    Vol. 56, p. 227-331
    DOI: 10.1016/B978-0-444-53886-4.00005-8
    Date of publication: 2011
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  • Fast optical source for quantum key distribution based on semiconductor optical amplifiers

     Jofre, Martí; Gardelein, A.; Anzolin, G.; Amaya, W.; CAPMANY FRANCOY, JOSÉ; Ursin, R.; Peñate, L.; Lopez, D.; San Juan, J.L.; Carrasco, J. A.; Garcia, F.; Torcal Milla, F. J.; Sanchez Brea, L. M.; Bernabeu, E.; Perdigues, J. M.; Jennewein, Thomas; Perez Torres, Juan; Mitchell, M. W.; Pruneri, Valerio
    Optics express
    Vol. 19, num. 5, p. 3825-3834
    DOI: 10.1364/OE.19.003825
    Date of publication: 2011
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  • Compact optical sources for quantum communications

     Jofre Cruanyes, Marc; Steinlechner, Fabian; Anzolin, G.; Perez Torres, Juan; Mitchell, M. W.; Pruneri, Valerio; Curty, M.
    International Symposium on Applied Sciences in Biomedical and Communication Technologies
    p. 1-2
    DOI: 10.1145/2093698.2093886
    Presentation's date: 2011
    Presentation of work at congresses

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  • Spatial characterization of two-photon states

     Osorio Tamayo, Clara Inés
    The Institute of Photonic Sciences, Universitat Politècnica de Catalunya
    Theses

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  • Spectrum shaping of paired photons

     Shi, Xiaojuan
    Department of Signal Theory and Communications, Universitat Politècnica de Catalunya
    Theses

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  • Measurement of the spatial shape of photons

     González Rodríguez, Noelia
    The Institute of Photonic Sciences, Universitat Politècnica de Catalunya
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    Properties of the spatial Wigner function of entangled photon pairs  Open access

     González, Noelia; Molina Terriza, Gabriel; Perez Torres, Juan
    Physical review A
    Vol. 80, num. 043804, p. 1-8
    DOI: 10.1103/PhysRevA.80.043804
    Date of publication: 2009-10
    Journal article

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    In this paper we analyze some important characteristics of the spatial Wigner function of entangled photon pairs. We show that the Wigner description of quantum states that live in the infinite-dimensional spacemomentum degree of freedom proves to be particularly useful. We propose an experimental configuration that can be used to retrieve the Wigner function of paired photons entangled in the spatial degree of freedom. In particular, it allows the full characterization of the paired photons emitted from a spontaneous parametric down-conversion source.

  • Bandwidth control of paired photons generated in monolithic Bragg reflection waveguides

     Abolghasem, P; Hendrych, M; Shi, X; Perez Torres, Juan; Helmy, AS
    Optics letters
    Vol. 34, num. 13, p. 2000-2002
    Date of publication: 2009-06
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  • Tailoring the spectral coherence of heralded single photons

     Perez Torres, Juan; Valencia, A; Torres-Company, V
    Optics letters
    Vol. 34, num. 8, p. 1177-1179
    Date of publication: 2009-04
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  • Angular dispersion: an enabling tool in nonlinear and quantum optics

     Valencia, Alejandra; Hendrych, Martin; Shi, Xiaojuan; Perez Torres, Juan
    International journal of quantum information
    Vol. 7, num. 1, p. 9-15
    DOI: 10.1142/S0219749909004906
    Date of publication: 2009
    Journal article

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