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

Frontiers in Optics

Robust, bright entangled photon source based on type-0, non-collinear phase-matching in periodically poled crystal

M. V. Jabir, G. K. Samanta

Published Jan 1, 2017• 0 citations
Publisher

Abstract

We demonstrate a novel source of high-brightness polarization entangled photons at room temperature. Using non-collinear phase-matching of PPKTP crystal we generate entangled state with 18.76kHz/mW/nm number of photon pairs, with fidelity ~0.975.
DOI
10.1364/fio.2017.jw4a.30

Related papers

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

Steinlechner, F., Trojek, P., Jofre, M. +9 more

We present a simple but highly efficient source of polarization-entangled photons based on spontaneous parametric down-conversion (SPDC) in bulk periodically poled potassium titanyl phosphate crystals (PPKTP) pumped by a 405 nm laser diode. Utilizing one of the highest available nonlinear coefficients in a non-degenerate, collinear type-0 phase-matching configuration, we generate polarization entanglement via the crossed-crystal scheme and detect 0.64 million photon pair events/s/mW, while maintaining an overlap fidelity with the ideal Bell state of 0.98 at a pump power of 0.025 mW.

•Apr 23, 2012•56 citations

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

Fabian Steinlechner, Pavel Trojek, Marc Jofre +9 more

We present a simple but highly efficient source of polarization-entangled photons based on spontaneous parametric down-conversion (SPDC) in bulk periodically poled potassium titanyl phosphate crystals (PPKTP) pumped by a 405 nm laser diode. Utilizing one of the highest available nonlinear coefficients in a non-degenerate, collinear type-0 phase-matching configuration, we generate polarization entanglement via the crossed-crystal scheme and detect 0.64 million photon pair events/s/mW, while maintaining an overlap fidelity with the ideal Bell state of 0.98 at a pump power of 0.025 mW.

arXiv:1204.5330•Optics Express•Apr 12, 2012•108 citations

Robust and bright polarization-entangled photon sources exploiting non-critical phase matching without periodic poling

Ilhwan Kim, Yosep Kim, Yong‐Su Kim +2 more

Entangled photon sources are essential for quantum information applications, including quantum computation, quantum communication, and quantum metrology. Periodically poled (PP) crystals are commonly used to generate bright photon sources through quasi-phase matching. However, fabricating uniform micron-scale periodic structures poses significant technical difficulties, typically limiting the crystal thickness to less than a millimeter. Here, we adopt non-critical phase matching to produce a robust and bright polarization-entangled photon source based on a bulk KTP crystal located in a Sagnac interferometer. This method is tolerant to variations in pump incidence angles and temperature, and theoretically offers about a 2.5-fold brightness enhancement compared to quasi-phase matching at a specific wavelength. Additionally, the absence of periodic poling allows for a larger crystal cross-section. Using a bulk KTP crystal without a PP structure, we experimentally produce the four Bell states with a brightness of 25.1 kHz/mW at a wavelength of 1079 nm, achieving purity, concurrence, and fidelity values close to 0.99. We believe our scheme will serve as a key building block for scalable and practical photonic quantum information applications.

arXiv:2409.07673•Optics Express•May 7, 2025•4 citations

Robust, high brightness, degenerate entangled photon source at room temperature

M. V. Jabir, G. K. Samanta

We report on a compact, simple and robust high brightness entangled photon source at room temperature. Based on a 30-mm-long periodically-poled potassium titanyl phosphate crystal, the source produces non-collinear, type-0, phase-matched, degenerate photons at 810 nm with spectral brightness as high as ~0.41 ± 0.02 (~0.025 ± 0.02) MHz/mW/nm for multi (single) mode fiber coupling. So far, this is the highest number of degenerate photons generated using a continuous-wave laser pumped bulk crystal and detected using multimode fiber. We have studied the dependence of pump focusing on the brightness of the generated photons collected using both multimode, and single mode fibers. For a fixed pump power and crystal parameters, the SPDC source has an optimum pump waist radius producing maximum number of paired photons. Combining the crystal in a novel system architecture comprised with Sagnac interferometer and polarizing optical elements, the source produces polarization entangled photon states with high spectral brightness. Even in the absence of any phase compensation, the entangled photon states detected using single mode fiber have a Bell's parameter, S = 2.63 ± 0.02, violating the Bell's inequality by nearly 32 standard deviations and fidelity of 0.975. The compact footprint, robust design, and room temperature operation, make our source ideal for various quantum communication experiments.

arXiv:1702.03633•Scientific Reports•Sep 27, 2017•57 citations

Bright source of narrowband polarization-entangled photons from a thick type-II ppKTP crystal

Omshankar, Vivek Venkataraman, Joyee Ghosh

We demonstrate a high brightness (∼2.36 × 10 5 pairs/s/mW) polarization-entangled photon-pair source at 800-nm via spontaneous parametric down-conversion (SPDC) in a 3-cm long type-II ppKTP crystal pumped unidirectionally in a single-pass geometry. A high coincidences-to-accidentals ratio (CAR ∼ 1200) depicted by our source indicates a strong temporal correlation between the generated photon pairs. This correlated photon source is tunable from collinear to non-collinear emission of the photons and over a range of signal/idler wavelengths ∼8 − 9 nm corresponding to a temperature range of 20–60°C. We measure a quantum state fidelity F >95% with the singlet entangled state | ψ − ⟩=12(| H V ⟩−| V H ⟩) along with a violation of the CHSH-Bell’s inequality by ∼485 standard deviations ( S = 2.68 ± 0.0014).

Optics Express•Dec 28, 2023•21 citations

Polarization-entangled photon-pair source obtained via type-II non-collinear SPDC process with PPKTP crystal

Sang Min Lee, Heonoh Kim, Myoungsik Cha +1 more

We demonstrate a polarization-entangled photon-pair source obtained via a type-II non-collinear quasi-phase-matched spontaneous parametric down-conversion process with a 10-mm periodically poled KTiOPO4 crystal, which is as stable and wavelength-tunable as the well-known Sagnac configuration scheme. A brightness of 4.2 kHz/mW is detected and a concurrence of 0.975 is estimated using quantum state tomography. Without loss of entanglement and brightness, the photon-pair wavelengths are tunable through control of the crystal temperature. This improvement is achieved using the non-collinear configuration and a stable interferometric distinguishability compensator.

arXiv:1512.07698•Optics Express•Feb 4, 2016•55 citations
We present a simple but highly efficient source of polarization-entangled photons based on spontaneous parametric down-conversion (SPDC) in bulk periodically poled potassium titanyl phosphate crystals (PPKTP) pumped by a 405 nm laser diode. Utilizing one of the highest available nonlinear coefficients in a non-degenerate, collinear type-0 phase-matching configuration, we generate polarization entanglement via the crossed-crystal scheme and detect 0.64 million photon pair events/s/mW, while maintaining an overlap fidelity with the ideal Bell state of 0.98 at a pump power of 0.025 mW.
We present a simple but highly efficient source of polarization-entangled photons based on spontaneous parametric down-conversion (SPDC) in bulk periodically poled potassium titanyl phosphate crystals (PPKTP) pumped by a 405 nm laser diode. Utilizing one of the highest available nonlinear coefficients in a non-degenerate, collinear type-0 phase-matching configuration, we generate polarization entanglement via the crossed-crystal scheme and detect 0.64 million photon pair events/s/mW, while maintaining an overlap fidelity with the ideal Bell state of 0.98 at a pump power of 0.025 mW.
Entangled photon sources are essential for quantum information applications, including quantum computation, quantum communication, and quantum metrology. Periodically poled (PP) crystals are commonly used to generate bright photon sources through quasi-phase matching. However, fabricating uniform micron-scale periodic structures poses significant technical difficulties, typically limiting the crystal thickness to less than a millimeter. Here, we adopt non-critical phase matching to produce a robust and bright polarization-entangled photon source based on a bulk KTP crystal located in a Sagnac interferometer. This method is tolerant to variations in pump incidence angles and temperature, and theoretically offers about a 2.5-fold brightness enhancement compared to quasi-phase matching at a specific wavelength. Additionally, the absence of periodic poling allows for a larger crystal cross-section. Using a bulk KTP crystal without a PP structure, we experimentally produce the four Bell states with a brightness of 25.1 kHz/mW at a wavelength of 1079 nm, achieving purity, concurrence, and fidelity values close to 0.99. We believe our scheme will serve as a key building block for scalable and practical photonic quantum information applications.
We report on a compact, simple and robust high brightness entangled photon source at room temperature. Based on a 30-mm-long periodically-poled potassium titanyl phosphate crystal, the source produces non-collinear, type-0, phase-matched, degenerate photons at 810 nm with spectral brightness as high as ~0.41 ± 0.02 (~0.025 ± 0.02) MHz/mW/nm for multi (single) mode fiber coupling. So far, this is the highest number of degenerate photons generated using a continuous-wave laser pumped bulk crystal and detected using multimode fiber. We have studied the dependence of pump focusing on the brightness of the generated photons collected using both multimode, and single mode fibers. For a fixed pump power and crystal parameters, the SPDC source has an optimum pump waist radius producing maximum number of paired photons. Combining the crystal in a novel system architecture comprised with Sagnac interferometer and polarizing optical elements, the source produces polarization entangled photon states with high spectral brightness. Even in the absence of any phase compensation, the entangled photon states detected using single mode fiber have a Bell's parameter, S = 2.63 ± 0.02, violating the Bell's inequality by nearly 32 standard deviations and fidelity of 0.975. The compact footprint, robust design, and room temperature operation, make our source ideal for various quantum communication experiments.
We demonstrate a high brightness (∼2.36 × 10 5 pairs/s/mW) polarization-entangled photon-pair source at 800-nm via spontaneous parametric down-conversion (SPDC) in a 3-cm long type-II ppKTP crystal pumped unidirectionally in a single-pass geometry. A high coincidences-to-accidentals ratio (CAR ∼ 1200) depicted by our source indicates a strong temporal correlation between the generated photon pairs. This correlated photon source is tunable from collinear to non-collinear emission of the photons and over a range of signal/idler wavelengths ∼8 − 9 nm corresponding to a temperature range of 20–60°C. We measure a quantum state fidelity F >95% with the singlet entangled state | ψ − ⟩=12(| H V ⟩−| V H ⟩) along with a violation of the CHSH-Bell’s inequality by ∼485 standard deviations ( S = 2.68 ± 0.0014).
We demonstrate a polarization-entangled photon-pair source obtained via a type-II non-collinear quasi-phase-matched spontaneous parametric down-conversion process with a 10-mm periodically poled KTiOPO4 crystal, which is as stable and wavelength-tunable as the well-known Sagnac configuration scheme. A brightness of 4.2 kHz/mW is detected and a concurrence of 0.975 is estimated using quantum state tomography. Without loss of entanglement and brightness, the photon-pair wavelengths are tunable through control of the crystal temperature. This improvement is achieved using the non-collinear configuration and a stable interferometric distinguishability compensator.