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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
    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.

    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
    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.

    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.

  • Nanostep height measurement via spatial mode projection

     Hermosa, Nathaniel; Rosales Guzmán, Carmelo; Pereira, Silvania F.; Perez Torres, Juan
    Optics letters
    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.

  • 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
    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
    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.

  • Digital coherent receiver for orbital angular momentum demultiplexing

     Belmonte Molina, Aniceto; Perez Torres, Juan
    Optics letters
    Date of publication: 2013-01-15
    Journal article

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  • Experimental detection of transverse particle movement with structured light

     Rosales Guzmán, Carmelo; Hermosa, Nathaniel; Belmonte Molina, Aniceto; Perez Torres, Juan
    Scientific reports
    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.

  • 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
    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
    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.

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    Helico-conical optical beams self-heal  Open access

     Hermosa, Nathaniel; Rosales Guzmán, Carmerlo; Perez Torres, Juan
    Optics letters
    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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    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
    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.

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

     Steinlechner, F.; Ramelow, Sven; Jofre, Marc; Gilaberte, Marta; Jennewein, Thomas; Perez Torres, Juan; Mitchell, Morgan W.; Pruneri, Valerio
    Optics express
    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%.

  • Puentes, Hermosa, and Torres reply

     Puentes, Graciana; Hermosa, Nathaniel; Perez Torres, Juan
    Physical review letters
    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

  • Steering and guiding light with light in a nanosuspension

     Terborg, Roland A.; Perez Torres, Juan; Volke-Sepulveda, Karen
    Optics letters
    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.

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

     Steinlechner, F.; 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
    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.

  • Transverse Doppler effect using engineered optical beams

     Rosales Guzmán, Carmelo; Hermosa, Nathaniel; Belmonte Molina, Aniceto; Perez Torres, Juan
    Coherent Laser Radar Conference
    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.

  • Weak interference in the high-signal regime

     Perez Torres, Juan; Puentes, G.; Hermosa, Nathaniel; Salazar Serrano, Luis Jose
    Optics express
    Date of publication: 2012-08-13
    Journal article

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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
    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

  • Light with enhanced optical chirality

     Rosales Guzmán, Carmerlo; Volke Sepulveda, K.; Perez Torres, Juan
    Optics letters
    Date of publication: 2012-09-01
    Journal article

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  • Self-homodyne detection of the light orbital angular momentum

     Belmonte Molina, Aniceto; Perez Torres, Juan
    Optics letters
    Date of publication: 2012-07-15
    Journal article

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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
    Date of publication: 2012-08
    Journal article

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  • A high-brightness source of polarization-entangled photons optimized for applications in free space

     Steinlechner, F.; 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
    Date of publication: 2012-04-23
    Journal article

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

     Svozilik, Jiri; Hendrych, Martin; Perez Torres, Juan
    Optics express
    Date of publication: 2012
    Journal article

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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
    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.

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

     Jofre Cruanyes, Marc; Anzolin, G.; Steinlechner, F.; NESTOR HUGO, OLIVERIO; Perez Torres, Juan; Pruneri, Valerio; Mitchell, M. W.
    Optics express
    Date of publication: 2012-05-21
    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
    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.

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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
    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.

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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
    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

  • 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
    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.

  • Optical communications: Multiplexing twisted light

     Perez Torres, Juan
    Nature photonics
    Date of publication: 2012-07
    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.

  • 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
    Date of publication: 2011
    Journal article

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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
    Date of publication: 2011-02-14
    Journal article

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  • 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
    Date of publication: 2011-02-25
    Journal article

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    Optical Doppler shift with structured light  Open access

     Belmonte Molina, Aniceto; Perez Torres, Juan
    Optics letters
    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

  • Engineering nonlinear optic sources of photonic entanglement

     Perez Torres, Juan; Banaszek, K.; Walmsley, I.A.
    Progress in optics
    Date of publication: 2011
    Journal article

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  • 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
    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.

  • Compact optical sources for quantum communications

     Jofre Cruanyes, Marc; Steinlechner, F.; Anzolin, G.; Perez Torres, Juan; Mitchell, M. W.; Pruneri, Valerio; Curty, M.
    International Symposium on Applied Sciences in Biomedical and Communication Technologies
    Presentation's date: 2011
    Presentation of work at congresses

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  • Measurement of the spatial shape of photons

     González Rodríguez, Noelia
    Defense's date: 2010-01-15
    The Institute of Photonic Sciences, Universitat Politècnica de Catalunya
    Theses

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  • Spectrum shaping of paired photons

     Shi, Xiaojuan
    Defense's date: 2010-03-05
    Department of Signal Theory and Communications, Universitat Politècnica de Catalunya
    Theses

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  • Spatial characterization of two-photon states

     Osorio Tamayo, Clara Inés
    Defense's date: 2010-03-12
    The Institute of Photonic Sciences, Universitat Politècnica de Catalunya
    Theses

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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
    Date of publication: 2009
    Journal article

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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
    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.

  • Tailoring the spectral coherence of heralded single photons

     Perez Torres, Juan; Valencia, A; Torres-Company, V
    Optics letters
    Date of publication: 2009-04
    Journal article

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

     Abolghasem, P; Hendrych, M; Shi, X; Perez Torres, Juan; Helmy, AS
    Optics letters
    Date of publication: 2009-06
    Journal article

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  • Ultrabroadband Biphotons Generated via Chirped Quasi-Phase-Matched Optical Parametric Down-Conversion

     Nasr, M B; Carrasco, S; Saleh, B E A; Sergienko, A V; Teich, M C; Perez Torres, Juan; Torner Sabata, Lluis; Hum, D S; Fejer, M M
    Physical review letters
    Date of publication: 2008-05
    Journal article

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  • Generation of indistinguishable and pure heralded single photons with tunable bandwidth

     Shi, X; Valencia, A; Hendrych, M; Perez Torres, Juan
    Optics letters
    Date of publication: 2008-04
    Journal article

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  • Generating ultra-broadband biphotons via chirped QPM down-conversion

     Teich, M C; Nasr, M B; Carrasco, S; Saleh, B E A; Sergienko, A V; Perez Torres, Juan; Torner Sabata, Lluis; Hum, D S; Fejer, M M
    Optics and photonics news
    Date of publication: 2008-12
    Journal article

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  • Correlations in orbital angular momentum of spatially entangled paired photons generated in parametric down-conversion

     Osorio, C I; Molina-Terriza, G; Perez Torres, Juan
    Physical review A
    Date of publication: 2008-01
    Journal article

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  • Twisted photons

     Molina-Terriza, G; Perez Torres, Juan; Torner Sabata, Lluis
    Nature physics
    Date of publication: 2007-05
    Journal article

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