Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Quantum Electronics and Laser Science Conference

Engineering correlated photons in nonlinear waveguides

Konrad Banaszek, A. U'Ren, I.A. Walmsey, Warren P. Grice

Published Jun 25, 2003• 0 citations
Publisher

Abstract

Summary form only given. Correlated photons are a key ingredient of many experiments testing the foundations of quantum mechanics and in quantum information processing. Many of these experiments harness entanglement by means of the nonclassical interference of photon pairs. A critical issue for such experiments is the mode matching of the photonic wave packets. Spontaneous parametric down-conversion is a well-established and practical method for generating pairs of correlated photons. High visibility interference of photon pairs generated by down-conversion in bulk crystals, a standard source for this type of experiments, can be achieved only by significant spatial filtering, which dramatically reduces the useful fraction of photon pairs. It also reduces the correlations between the presence of photons, thus opening for example the efficiency loophole in tests of Bell's inequalities. Nonlinear waveguides, compared to bulk crystals, offer several advantages as a source of correlated photon pairs. Most importantly, the waveguide structure provides a means to control precisely the spatial characteristics of generated photons, because of the well-defined transverse modes of the guide. in addition, nonlinear waveguides offer both higher pair production rates by utilizing the technique of quasiphase matching, and possibilities for spectral mode engineering.

DOI
10.1109/qels.2002.1031026

Related papers

Generation of correlated photons in controlled spatial modes by downconversion in nonlinear waveguides

Konrad Banaszek, Alfred B. U’Ren, Ian A. Walmsley

We report the observation of correlated photon pairs generated by spontaneous parametric downconversion of a 400-nm pump pulse in a quasi-phase-matched KTiOPO(4) nonlinear waveguide. The highest ratio of coincidence to single-photon count rates observed near 800 nm exceeds 18%. This suggests that nonlinear waveguides will be a promising source of correlated photons for metrology and quantum information processing applications. We also discuss possibilities of controlling the spatial characteristics of the downconverted photons produced in multimode waveguide structures.

arXiv:quant-ph/0103026•Optics Letters•Sep 1, 2001•128 citations

Nonlocal Parametric Down-Conversion in Multi-Mode Nonlinear Waveguide Arrays

Frank Setzpfandt, Alexander S. Solntsev, Thomas Pertsch +1 more

The generation of multi-photon quantum states in integrated waveguiding structures provides a route to the creation of quantum optical chips. In particular, the simultaneous generation of photons through spontaneous parametric down-conversion (SPDC) and their quantum walks in nonlinear waveguide arrays (WGAs) can be used to produce strongly spatially entangled biphoton states [1] with applications for quantum search algorithms [2]. Whereas up to now only arrays of single-mode nonlinear waveguides have been considered for SPDC, in general the waveguides may support several guided modes, which were demonstrated to strongly affect nonlinear wave mixing in the classical regime [3]. Here we show that using higher order modes for SPDC has a significant influence on the generated two-photon states and gives additional means to control them. In particular, we employ the symmetry of the modes to engineer effectively nonlocal photon pair generation by SPDC.

European Quantum Electronics Conference (EQEC)•Jan 1, 2015•0 citations

Effiziente Erzeugung verschränkter Photonenpaare

Markus Oberparleiter

Efficient Generation of Entangled Photon-Pairs The first experiments with correlated photons have been performed in the context of EPR-Bell experiments on the realistic and local properties of quantum mechanics. The source used there produced pairs of polarization entangled photons from a 2-photon decay of Calcium atoms. The technical requirements of these experiments were high (vacuum systems, stronge dye-lasers, etc.) whereas the efficiency of the source was quite low. An important step forward was the introduction of spontaneous parametric down conversion (SPDC), which has become the most common source in quantum optics for generating correlated or entangled photon pairs. In this process photons of an intense pump laser convert to photon pairs in an optical nonlinear crystal. Conservation of energy and momentum leads to strong correlations between the generated photons. With this kind of two-photon source it was possible to realize or improve many experiments on the foundations of quantum mechanics addressing the EPR-Paradoxon and in the new field of quantum information. But again, more advanced experiments and applications suffer from the limited ef- ficiency of the fluorescence process. Many photon pairs are lost by spatial and spectral filtering, which is necessary to achieve polarization entanglement and long coherence times. Different techniques have been implemented to increase the number of photon pairs using two-crystal arrangements, focusing techniques or periodically poled crystals. Most of these methods have the disadvantage that no entangled photons have been observed. It is the aim of this work to increase the yield and to improve the mode definition of entangled photon pairs generated by resonant enhancement of the pump mode and the fluorescence modes. As a first step a linear cavity for the pump mode was realized. Since the conversion probability is proportional to the pump power it was possible to increase the photon pair count rate by factor of 7 over the previous source. Besides the possibility of further improvement on already established pair correlation experiments, such an enhancement allows to build a compact source for photon pairs, in which an expensive argon-ion laser is replaced by a cheap diode laser. Among other applications such sources are of strong interest for quantum cryptography. 3 In many quantum information experiments optical fibers are use to carry the photons over long distance. Therefore, light from the parametric down-conversion source has to be efficiently coupled into fibers. In the second part we report on a new method to optimize collection efficiency by matching the angular distribution of the parametric fluorescence to the spatial mode of an optical fiber. By using this technique, we detected 366500 polarization-entangled photon pairs per second in the near-infrared region in single-mode optical fibers for 465 mW pump power (at 351.1 nm) with a 2 mm BBOcrystal. The entanglement of the photon pairs was verified by measuring polarization correlations of more than 96% in a HV-basis and in a ±45◦-basis. To our knowledge, such enormous count rates of highly entangled photon pairs have not been reached yet with any other technique. In the third part of this thesis we investigated the process of parametric downconversion in a cavity which is resonant to certain longitudinal down-conversion modes only. The idea of placing the parametric down-conversion source inside a cavity is not new. Such a device is usually referred to as a single or double resonant optical parametric oscillator (OPO) and is mainly used to generate squeezed quantum states. In that kind of application the system is operating close to but still under the threshold of oscillation. In our application the situation is quite different. The system is operating far below threshold so that mainly spontaneous emission occurs. In that mode correlations between single photons can still be observed. But bouncing the light back and forth inside the cavity increases the interaction length and hence enhances the signal levels of the down-conversion fields. Further, by resonating two certain modes only, the bandwidth is reduced by orders of magnitude and the coherence time is found to be inverse proportional to the bandwidth. A similar experiment has already been realized with a type-I parametric down-converter in the resonator. We have tried to realize a compact double resonant OPO far below threshold with a type-II parametric down-converter in a high-finesse cavity to realize a bright source of entangled photon pairs with extremely narrow bandwidth.

•Jan 1, 2002•1 citation

Efficiency of entangled photon pair generation in bulk crystals and waveguides: a comparison

Anthony Leverrier, Anton Zavriyev, Alexei S. Trifonov

The efficiency of spontaneous parametric down conversion is calculated and measured for several nonlinear crystals and waveguides in single spatial mode regime. Efficiency of waveguide sources is found to be far superior compared to the bulk crystal sources.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE•May 5, 2006•1 citation

Spontaneous Parametric Down-Conversion and Quantum Walks in Arrays of Quadratic Nonlinear Waveguides

Alexander S. Solntsev, Andrey A. Sukhorukov, Dragomir N. Neshev +1 more

We analyze the process of photon-pair generation with simultaneous quantum walks in a quadratic nonlinear waveguide array. We demonstrate that the spontaneous parametric down-conversion in the array allows for creating quantum states with strongly pronounced spatial correlations, which are qualitatively different from those possible in bulk crystals or through quantum walks in linear waveguide arrays. Most importantly, the photon correlations can be controlled entirely classically by varying the spatial profile of the pump beam or the phase-matching conditions.

arXiv:1108.6116•Physical Review Letters•Jan 10, 2012•92 citations

Counterpropagating entangled photons in a periodically poled nonlinear waveguide

Mark C. Booth, Mete Atatüre, Giovanni Di Giuseppe +3 more

Entangled photons, which may be generated through the process of spontaneous parametric down-conversion (SPDC) in a crystal with /spl chi//sup (2)/ nonlinearity, have long been in the spotlight for quantum-optics experiments. The generation of entangled photons by quasi-phase matching (QPM) in lithium niobate offers the promise of increased photon-pair production and, with the integration of a waveguide structure, control of the spatial characteristics of the down-converted photons. It turns out that the use of a waveguide structure, in conjunction with periodic poling to achieve quasi-phase matching, offers another critically important feature: the possibility of generating counterpropagating signal and idler photons. We consider the conditions required for generating counterpropagating photon beams and explore some of the unique properties of this source of light using a periodically poled LiNbO/sub 3/ waveguide.

IEEE Lasers and Electro-Optics Society Annual Meeting (LEOS)•Jun 26, 2003•2 citations
Summary form only given. Correlated photons are a key ingredient of many experiments testing the foundations of quantum mechanics and in quantum information processing. Many of these experiments harness entanglement by means of the nonclassical interference of photon pairs. A critical issue for such experiments is the mode matching of the photonic wave packets. Spontaneous parametric down-conversion is a well-established and practical method for generating pairs of correlated photons. High visibility interference of photon pairs generated by down-conversion in bulk crystals, a standard source for this type of experiments, can be achieved only by significant spatial filtering, which dramatically reduces the useful fraction of photon pairs. It also reduces the correlations between the presence of photons, thus opening for example the efficiency loophole in tests of Bell's inequalities. Nonlinear waveguides, compared to bulk crystals, offer several advantages as a source of correlated photon pairs. Most importantly, the waveguide structure provides a means to control precisely the spatial characteristics of generated photons, because of the well-defined transverse modes of the guide. in addition, nonlinear waveguides offer both higher pair production rates by utilizing the technique of quasiphase matching, and possibilities for spectral mode engineering.
We report the observation of correlated photon pairs generated by spontaneous parametric downconversion of a 400-nm pump pulse in a quasi-phase-matched KTiOPO(4) nonlinear waveguide. The highest ratio of coincidence to single-photon count rates observed near 800 nm exceeds 18%. This suggests that nonlinear waveguides will be a promising source of correlated photons for metrology and quantum information processing applications. We also discuss possibilities of controlling the spatial characteristics of the downconverted photons produced in multimode waveguide structures.
The generation of multi-photon quantum states in integrated waveguiding structures provides a route to the creation of quantum optical chips. In particular, the simultaneous generation of photons through spontaneous parametric down-conversion (SPDC) and their quantum walks in nonlinear waveguide arrays (WGAs) can be used to produce strongly spatially entangled biphoton states [1] with applications for quantum search algorithms [2]. Whereas up to now only arrays of single-mode nonlinear waveguides have been considered for SPDC, in general the waveguides may support several guided modes, which were demonstrated to strongly affect nonlinear wave mixing in the classical regime [3]. Here we show that using higher order modes for SPDC has a significant influence on the generated two-photon states and gives additional means to control them. In particular, we employ the symmetry of the modes to engineer effectively nonlocal photon pair generation by SPDC.
Efficient Generation of Entangled Photon-Pairs The first experiments with correlated photons have been performed in the context of EPR-Bell experiments on the realistic and local properties of quantum mechanics. The source used there produced pairs of polarization entangled photons from a 2-photon decay of Calcium atoms. The technical requirements of these experiments were high (vacuum systems, stronge dye-lasers, etc.) whereas the efficiency of the source was quite low. An important step forward was the introduction of spontaneous parametric down conversion (SPDC), which has become the most common source in quantum optics for generating correlated or entangled photon pairs. In this process photons of an intense pump laser convert to photon pairs in an optical nonlinear crystal. Conservation of energy and momentum leads to strong correlations between the generated photons. With this kind of two-photon source it was possible to realize or improve many experiments on the foundations of quantum mechanics addressing the EPR-Paradoxon and in the new field of quantum information. But again, more advanced experiments and applications suffer from the limited ef- ficiency of the fluorescence process. Many photon pairs are lost by spatial and spectral filtering, which is necessary to achieve polarization entanglement and long coherence times. Different techniques have been implemented to increase the number of photon pairs using two-crystal arrangements, focusing techniques or periodically poled crystals. Most of these methods have the disadvantage that no entangled photons have been observed. It is the aim of this work to increase the yield and to improve the mode definition of entangled photon pairs generated by resonant enhancement of the pump mode and the fluorescence modes. As a first step a linear cavity for the pump mode was realized. Since the conversion probability is proportional to the pump power it was possible to increase the photon pair count rate by factor of 7 over the previous source. Besides the possibility of further improvement on already established pair correlation experiments, such an enhancement allows to build a compact source for photon pairs, in which an expensive argon-ion laser is replaced by a cheap diode laser. Among other applications such sources are of strong interest for quantum cryptography. 3 In many quantum information experiments optical fibers are use to carry the photons over long distance. Therefore, light from the parametric down-conversion source has to be efficiently coupled into fibers. In the second part we report on a new method to optimize collection efficiency by matching the angular distribution of the parametric fluorescence to the spatial mode of an optical fiber. By using this technique, we detected 366500 polarization-entangled photon pairs per second in the near-infrared region in single-mode optical fibers for 465 mW pump power (at 351.1 nm) with a 2 mm BBOcrystal. The entanglement of the photon pairs was verified by measuring polarization correlations of more than 96% in a HV-basis and in a ±45◦-basis. To our knowledge, such enormous count rates of highly entangled photon pairs have not been reached yet with any other technique. In the third part of this thesis we investigated the process of parametric downconversion in a cavity which is resonant to certain longitudinal down-conversion modes only. The idea of placing the parametric down-conversion source inside a cavity is not new. Such a device is usually referred to as a single or double resonant optical parametric oscillator (OPO) and is mainly used to generate squeezed quantum states. In that kind of application the system is operating close to but still under the threshold of oscillation. In our application the situation is quite different. The system is operating far below threshold so that mainly spontaneous emission occurs. In that mode correlations between single photons can still be observed. But bouncing the light back and forth inside the cavity increases the interaction length and hence enhances the signal levels of the down-conversion fields. Further, by resonating two certain modes only, the bandwidth is reduced by orders of magnitude and the coherence time is found to be inverse proportional to the bandwidth. A similar experiment has already been realized with a type-I parametric down-converter in the resonator. We have tried to realize a compact double resonant OPO far below threshold with a type-II parametric down-converter in a high-finesse cavity to realize a bright source of entangled photon pairs with extremely narrow bandwidth.
We analyze the process of photon-pair generation with simultaneous quantum walks in a quadratic nonlinear waveguide array. We demonstrate that the spontaneous parametric down-conversion in the array allows for creating quantum states with strongly pronounced spatial correlations, which are qualitatively different from those possible in bulk crystals or through quantum walks in linear waveguide arrays. Most importantly, the photon correlations can be controlled entirely classically by varying the spatial profile of the pump beam or the phase-matching conditions.
Entangled photons, which may be generated through the process of spontaneous parametric down-conversion (SPDC) in a crystal with /spl chi//sup (2)/ nonlinearity, have long been in the spotlight for quantum-optics experiments. The generation of entangled photons by quasi-phase matching (QPM) in lithium niobate offers the promise of increased photon-pair production and, with the integration of a waveguide structure, control of the spatial characteristics of the down-converted photons. It turns out that the use of a waveguide structure, in conjunction with periodic poling to achieve quasi-phase matching, offers another critically important feature: the possibility of generating counterpropagating signal and idler photons. We consider the conditions required for generating counterpropagating photon beams and explore some of the unique properties of this source of light using a periodically poled LiNbO/sub 3/ waveguide.