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

arXiv:2609.37514

Multi-Parameter Error Mitigation in Parametric Down-Conversion via SU(1, 1) Composite Segmentation

Nastaran Ragerdi Kashani, Rouhollah Karimzadeh

physics.opticsquant-phSubmitted Sep 29, 2026• Announced Sep 30, 2026• 0 citations
arXivHTMLPDF

Abstract

Spontaneous parametric down-conversion is a primary resource for generating non-classical light, yet phase mismatch fluctuations from temperature drift, angular misalignment, and domain fabrication errors reduce pair-generation efficiency and phase stability. Here, we analyze error mitigation in spontaneous parametric down-conversion using composite segmentation governed by SU(1, 1) spatial dynamics. We show that odd spatial Fourier harmonics preserve error-cancellation flatness with pair-generation rates scaling asymptotically as $m^{-2}$, while a coordinate-dilation symmetry provides a design prescription for translating configurations across distinct operating wavelengths (405, 532, and 775 nm). Furthermore, an open-loop thermo-optic bias counteracts off-axis angular drift to broaden the 90%-efficiency angular acceptance half-width by 3.46x, and up to two missing poling domains are tolerated with no numerically resolved loss in relative conversion efficiency. Across a 5$^\circ$C thermal window, the generated pairs sustain a relative conversion efficiency of $η\ge 0.954$ with the modeled phase-coherence metric remaining above 0.95, providing a structurally robust approach for entangled photon generation without requiring continuous closed-loop feedback stabilization.

Comments
7 pages, 4 figures, 1 table

Related papers

Efficient Robust Spontaneous Parametric Down‐Conversion via Detuning Modulated Composite Segments Designs

Muhammad Erew, Yuval Reches, Ofir Yesharim +3 more

ABSTRACT Spontaneous parametric down conversion (SPDC) holds a pivotal role in quantum physics, facilitating the creation of entangled photon pairs, heralded single photons and squeezed light, critical resources for many applications in quantum technologies. However, their production is susceptible to physical variations, posing limitations on their robust utility. To overcome these limitations, this work introduces a method to significantly enhance the reliability of entangled photon pair generation. This approach involves introducing a composite design scheme to the SPDC process. The design is based on the development of a theoretical composite segments framework for SU(1,1), offering increased error resilience and robustness of the process. The practical application is experimentally demonstrated by modulating the nonlinear coefficient of a KTP crystal for degenerate 532–1064 nm conversion, resulting in an effective sevenfold improvement in stability of photon‐pair generation and coincidence rate against temperature fluctuations compared to conventional quasi‐phase‐matching techniques. Furthermore, the presented concept is applicable to other physical systems that exhibit SU(1,1) dynamics. This methodology can create a leap forward in quantum technologies by significantly enhancing stability and error tolerance, thus paving the way for a new generation of entangled photon sources, holding promise for quantum information processing, communication, and precision measurement applications.

arXiv:2410.10985•Laser & Photonics Review•Oct 30, 2025•1 citation

Numerical framework for Type-I SPDC using Python: photon emission and entanglement analysis

Ahmed Albashir, Fadel Al-Sharif, Aboalqasim Alqat +1 more

Spontaneous Parametric Down-Conversion (SPDC) serves as a fundamental physical resource for generating entangled photon pairs. However, modeling its multi-dimensional phase-space dynamics under realistic laboratory conditions remains computationally demanding. Consequently, there is a growing demand for physically faithful digital datasets that can support quantum-optics research prior to physical laboratory implementation. In this work, we present an end-to-end, physically constrained numerical framework designed to generate reusable synthetic datasets for degenerate Type-I SPDC within β-BBO crystals (405 nm → 810 nm). To ensure the numerical outputs can function as a reliable resource for downstream analysis, the framework is subjected to a multi-level validation architecture. The structural integrity of the generated data is first confirmed through independent conservation-law checks, achieving energy conservation with a relative error of 0.000247% and preserving strict transverse momentum anti-correlations (ρ ≈ −0.99999). Furthermore, the dataset’s capacity to retain hidden quantum correlations is verified through high-dimensional modal analysis. Laguerre-Gaussian projections confirm the preservation of nonclassical modal correlations through an effective Schmidt number of K = 2.668 within the computational basis. Finally, The Bell-CHSH analysis validates the implementation of the post-processing pipeline (Sideal = 2.82843) rather than the physical fidelity of the generated SPDC source. When practical laboratory constraints—such as spatial aperture masking and dark counts—are applied, the dataset robustly maintains a mathematically verified violation of Sexp = 2.72992. By bridging fundamental quantum optics with modeled empirical imperfections, this open-science platform yields structurally validated synthetic data, providing a reusable foundation for future studies in entanglement, interference, and quantum information processing.

Journal of the Optical Society of America B•Sep 8, 2026•0 citations

Spontaneous parametric down-conversion in ultrathin samples

Maria V. Chekhova

Miniaturization of nonlinear optical elements is one of the major trends of modern photonics. In particular, in the ‘flatoptics’ geometry, the sample is ultrathin along the light propagation direction. For nonlinear optical effects in such samples, phase matching is satisfied automatically, which allows for the use of materials with giant nonlinear susceptibilities. The tiny thickness reduces the efficiency but it can be compensated for by using geometric and material resonances. Recently also spontaneous parametric down-conversion (SPDC), leading to the generation of entangled photons, has been implemented in ultrasmall sources: subwavelength layers, metasurfaces, even nanoantennas. The lifted constraint of phase matching gives to SPDC even more freedom than to classical frequency conversion effects. The reason is that SPDC, as a spontaneous effect, is stimulated by quantum vacuum fluctuations, which populate all modes uniformly. SPDC in ultrathin samples demonstrates very broad spectral and angular width, extremely high degrees of continuous-variable entanglement, tunable polarization entanglement, and orders of magnitude enhancement of photon pair production rate due to the geometric resonances of dielectric metasurfaces.

SPIE Conference on Nonlinear Optics and its Applications•Jun 20, 2024•1 citation

Gaussian mode coupling of spectrally broadband photons from bulk spontaneous parametric down-conversion: A spatial-spectral mode analysis of fiber coupling

Carlos Sevilla-Gutiérrez, Varun Raj Kaipalath, Fabian Steinlechner

Photon sources based on spontaneous parametric down-conversion (SPDC) are central to experimental quantum optics and quantum technologies. Their performance is commonly quantified by three metrics: pair-collection probability, heralding efficiency, and spectral purity. In bulk-crystal SPDC, these metrics are known to be mutually constrained, yet the physical origin of the resulting trade-offs is often obscured. We show that these trade-offs originate from the frequency-dependent population of discrete spatial modes in the SPDC emission. By performing a Laguerre-Gauss mode decomposition at each frequency component, we show how spectral-spatial non-separability impacts collection probability, heralding efficiency, and purity. We apply this framework to two widely used quasi-phase-matching configurations: collinear degenerate type-0 and type-II SPDC in periodically poled bulk crystals, and quantify how different phase-matching functions shape the spectral-spatial mode structure. In particular, for type-II SPDC we compare standard periodically poled and aperiodically poled Gaussian phase matching. We experimentally validate some of our theoretical results using spatial- and spectral-projection measurements. This spectral-spatial mode analysis provides a quantitative and predictive framework for understanding and engineering bulk-crystal photon sources, enabling systematic multi-parameter optimization beyond qualitative design guidelines.

quant-pharXiv:2602.23238•Physical Review A•Feb 27, 2026•1 citation

Angular and temperature dependence of photon pair rates in spontaneous parametric down-conversion from a periodically poled crystal

G. Daniel Jimenez, Veneranda G. Garces, Kevin A. O’Donnell

We present a theoretical and experimental study of the angular and temperature dependence of the photon pairs produced by spontaneous parametric down-conversion in a periodically poled KTP crystal. In the experiment, two detectors are placed at different angles in the emitted light, and the detected photon pair rate is measured as a function of one angle or of crystal temperature. In the theoretical work, exact results for the pair rates are obtained through importance-sampled numerical integration of the fourth-order coherence function over regions representing the experimental integration parameters. Conditions studied range from well-resolved results in which detector angular and filter bandwidth integration effects are negligible, to other cases in which such effects are large and pair rates exceed ${10}^{5}\phantom{\rule{4pt}{0ex}}{\mathrm{s}}^{\ensuremath{-}1}$. Throughout these cases, good agreement is often seen between experimental and theoretical results, while some differences that are noted provide insight into the actual crystal quasi-phase-matching function.

Physical Review A•Aug 11, 2017•4 citations

Spontaneous Parametric Down-Conversion Photon Pair Generation in a Small Footprint X-Cut Periodic Poled Lithium Niobate Micro-Resonator

Hyeon Hwang, Woojin Noh, Mohamad Reza Nurrahman +5 more

Spontaneous parametric down-conversion (SPDC) has been utilized in generating non-classical light, such as correlated photon pairs and squeezed light, significantly influencing optical quantum information research. Advances in thinfilm lithium niobate (TFLN) technologies have brought the benefits of χ(2)nonlinearity from bulk optics to integrated photonics. Targeting fully exploitation of high Electro-optic (EO) controllability and the periodic poled lithium niobate (PPLN), enabling quasi-phase matching (QPM), offer the realization especially under the X-cut based platform [1]–[3]. Moreover, the small footprint is also key figure of merit for efficient processing of SPDC spectrum. In this work, we demonstrate SPDC photon pair generation in a small footprint size with a 0.614 nm FSR at the IR wavelength, based on X-cut PPLN racetrack resonator.

Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC)•Jun 23, 2025•0 citations
Spontaneous parametric down-conversion is a primary resource for generating non-classical light, yet phase mismatch fluctuations from temperature drift, angular misalignment, and domain fabrication errors reduce pair-generation efficiency and phase stability. Here, we analyze error mitigation in spontaneous parametric down-conversion using composite segmentation governed by SU(1, 1) spatial dynamics. We show that odd spatial Fourier harmonics preserve error-cancellation flatness with pair-generation rates scaling asymptotically as m−2m^{-2}m−2, while a coordinate-dilation symmetry provides a design prescription for translating configurations across distinct operating wavelengths (405, 532, and 775 nm). Furthermore, an open-loop thermo-optic bias counteracts off-axis angular drift to broaden the 90%-efficiency angular acceptance half-width by 3.46x, and up to two missing poling domains are tolerated with no numerically resolved loss in relative conversion efficiency. Across a 5∘^\circ∘C thermal window, the generated pairs sustain a relative conversion efficiency of η≥0.954η\ge 0.954η≥0.954 with the modeled phase-coherence metric remaining above 0.95, providing a structurally robust approach for entangled photon generation without requiring continuous closed-loop feedback stabilization.
ABSTRACT Spontaneous parametric down conversion (SPDC) holds a pivotal role in quantum physics, facilitating the creation of entangled photon pairs, heralded single photons and squeezed light, critical resources for many applications in quantum technologies. However, their production is susceptible to physical variations, posing limitations on their robust utility. To overcome these limitations, this work introduces a method to significantly enhance the reliability of entangled photon pair generation. This approach involves introducing a composite design scheme to the SPDC process. The design is based on the development of a theoretical composite segments framework for SU(1,1), offering increased error resilience and robustness of the process. The practical application is experimentally demonstrated by modulating the nonlinear coefficient of a KTP crystal for degenerate 532–1064 nm conversion, resulting in an effective sevenfold improvement in stability of photon‐pair generation and coincidence rate against temperature fluctuations compared to conventional quasi‐phase‐matching techniques. Furthermore, the presented concept is applicable to other physical systems that exhibit SU(1,1) dynamics. This methodology can create a leap forward in quantum technologies by significantly enhancing stability and error tolerance, thus paving the way for a new generation of entangled photon sources, holding promise for quantum information processing, communication, and precision measurement applications.
Spontaneous Parametric Down-Conversion (SPDC) serves as a fundamental physical resource for generating entangled photon pairs. However, modeling its multi-dimensional phase-space dynamics under realistic laboratory conditions remains computationally demanding. Consequently, there is a growing demand for physically faithful digital datasets that can support quantum-optics research prior to physical laboratory implementation. In this work, we present an end-to-end, physically constrained numerical framework designed to generate reusable synthetic datasets for degenerate Type-I SPDC within β-BBO crystals (405 nm → 810 nm). To ensure the numerical outputs can function as a reliable resource for downstream analysis, the framework is subjected to a multi-level validation architecture. The structural integrity of the generated data is first confirmed through independent conservation-law checks, achieving energy conservation with a relative error of 0.000247% and preserving strict transverse momentum anti-correlations (ρ ≈ −0.99999). Furthermore, the dataset’s capacity to retain hidden quantum correlations is verified through high-dimensional modal analysis. Laguerre-Gaussian projections confirm the preservation of nonclassical modal correlations through an effective Schmidt number of K = 2.668 within the computational basis. Finally, The Bell-CHSH analysis validates the implementation of the post-processing pipeline (Sideal = 2.82843) rather than the physical fidelity of the generated SPDC source. When practical laboratory constraints—such as spatial aperture masking and dark counts—are applied, the dataset robustly maintains a mathematically verified violation of Sexp = 2.72992. By bridging fundamental quantum optics with modeled empirical imperfections, this open-science platform yields structurally validated synthetic data, providing a reusable foundation for future studies in entanglement, interference, and quantum information processing.
Miniaturization of nonlinear optical elements is one of the major trends of modern photonics. In particular, in the ‘flatoptics’ geometry, the sample is ultrathin along the light propagation direction. For nonlinear optical effects in such samples, phase matching is satisfied automatically, which allows for the use of materials with giant nonlinear susceptibilities. The tiny thickness reduces the efficiency but it can be compensated for by using geometric and material resonances. Recently also spontaneous parametric down-conversion (SPDC), leading to the generation of entangled photons, has been implemented in ultrasmall sources: subwavelength layers, metasurfaces, even nanoantennas. The lifted constraint of phase matching gives to SPDC even more freedom than to classical frequency conversion effects. The reason is that SPDC, as a spontaneous effect, is stimulated by quantum vacuum fluctuations, which populate all modes uniformly. SPDC in ultrathin samples demonstrates very broad spectral and angular width, extremely high degrees of continuous-variable entanglement, tunable polarization entanglement, and orders of magnitude enhancement of photon pair production rate due to the geometric resonances of dielectric metasurfaces.
Photon sources based on spontaneous parametric down-conversion (SPDC) are central to experimental quantum optics and quantum technologies. Their performance is commonly quantified by three metrics: pair-collection probability, heralding efficiency, and spectral purity. In bulk-crystal SPDC, these metrics are known to be mutually constrained, yet the physical origin of the resulting trade-offs is often obscured. We show that these trade-offs originate from the frequency-dependent population of discrete spatial modes in the SPDC emission. By performing a Laguerre-Gauss mode decomposition at each frequency component, we show how spectral-spatial non-separability impacts collection probability, heralding efficiency, and purity. We apply this framework to two widely used quasi-phase-matching configurations: collinear degenerate type-0 and type-II SPDC in periodically poled bulk crystals, and quantify how different phase-matching functions shape the spectral-spatial mode structure. In particular, for type-II SPDC we compare standard periodically poled and aperiodically poled Gaussian phase matching. We experimentally validate some of our theoretical results using spatial- and spectral-projection measurements. This spectral-spatial mode analysis provides a quantitative and predictive framework for understanding and engineering bulk-crystal photon sources, enabling systematic multi-parameter optimization beyond qualitative design guidelines.
We present a theoretical and experimental study of the angular and temperature dependence of the photon pairs produced by spontaneous parametric down-conversion in a periodically poled KTP crystal. In the experiment, two detectors are placed at different angles in the emitted light, and the detected photon pair rate is measured as a function of one angle or of crystal temperature. In the theoretical work, exact results for the pair rates are obtained through importance-sampled numerical integration of the fourth-order coherence function over regions representing the experimental integration parameters. Conditions studied range from well-resolved results in which detector angular and filter bandwidth integration effects are negligible, to other cases in which such effects are large and pair rates exceed ${10}^{5}\phantom{\rule{4pt}{0ex}}{\mathrm{s}}^{\ensuremath{-}1}$. Throughout these cases, good agreement is often seen between experimental and theoretical results, while some differences that are noted provide insight into the actual crystal quasi-phase-matching function.
Spontaneous parametric down-conversion (SPDC) has been utilized in generating non-classical light, such as correlated photon pairs and squeezed light, significantly influencing optical quantum information research. Advances in thinfilm lithium niobate (TFLN) technologies have brought the benefits of χ(2)nonlinearity from bulk optics to integrated photonics. Targeting fully exploitation of high Electro-optic (EO) controllability and the periodic poled lithium niobate (PPLN), enabling quasi-phase matching (QPM), offer the realization especially under the X-cut based platform [1]–[3]. Moreover, the small footprint is also key figure of merit for efficient processing of SPDC spectrum. In this work, we demonstrate SPDC photon pair generation in a small footprint size with a 0.614 nm FSR at the IR wavelength, based on X-cut PPLN racetrack resonator.