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

Scientific Reports

Towards generation of hybrid entangled photon pairs by spectrally overlapping intermodal-vectorial four-wave mixing bands in optical fibers

Andrzej Gawlik, Marta Bernaś, Kinga Żołnacz, Karol Tarnowski

Published Nov 27, 2025• 0 citations
Publisher

Abstract

Optical fiber-based sources of photon pairs with hybrid entanglement across multiple degrees of freedom are essential for a wide range of quantum technologies, while remaining compatible with existing communication networks. In this paper, we use a birefringent few-mode fiber to demonstrate an intermodal-vectorial four-wave mixing process that generates two pairs of spectrally overlapping signal-idler bands. Using phase-matching conditions, we show that the pairs of bands become spectrally indistinguishable when the group refractive indices of the signal and idler modes intersect at the pump wavelength. Our theoretical predictions are confirmed through experimental observations and corroborated by numerical simulations. Furthermore, we introduce the two-photon state associated with the overlapping bands, which simultaneously exhibits entanglement in a single degree of freedom and hybrid entanglement across multiple degrees of freedom. We also explain how the type and degree of entanglement can be controlled by tailoring the spectral overlap between the signal-idler bands. This study presents a promising scheme for a fiber-based source of photon pairs with entanglement spanning the spatial, polarization, and frequency degrees of freedom.

DOI
10.1038/s41598-025-29082-3

Related papers

Spectrally indistinguishable intermodal-vectorial four-wave-mixing in birefringent few-mode fibers for spatial-polarization-frequency hybrid-entangled photon-pairs generation

Andrzej Gawlik, Marta Bernaś, Kinga Żołnacz +1 more

In this paper, we use a birefringent few-mode fiber to demonstrate an intermodal-vectorial four-wave mixing process that generates two pairs of spectrally overlapping signal-idler bands. Using phase-matching conditions, we show that the pairs of bands become spectrally indistinguishable when the group refractive indices of the signal and idler modes intersect at the pump wavelength. Our theoretical predictions are confirmed through experimental observations corroborated by numerical simulations. Furthermore, we introduce the two-photon state associated with the overlapping bands, which exhibits hybrid entanglement in spatial-polarization-frequency degrees of freedom. We explain that its degree of entanglement can be manipulated by tailoring the spectral position of the overlapping pairs of bands with respect to the Raman band and varying the excitation ratio of the pump modes. This study introduces a scheme for a fiber-based source of photon pairs with spatial-polarization-frequency entanglement.

arXiv:2412.09214•Dec 12, 2024•1 citation

Intermodal-Vectorial Four-Wave Mixing in Few-Mode Fibers for Generation of Photon Pairs with Spatial-Polarization-Frequency Hybrid Entanglement

Andrzej Gawlik, Marta Bernaś, Kinga Żołnacz +1 more

Four-wave mixing (FWM) in optical fibers is a nonlinear optical process which can be used to generate photon pairs with hybrid entanglement in multiple degrees of freedom (DOFs), including frequency, polarization, spatial mode, or angular momentum [1]. Until now, the realizations of entanglements in the DOFs: energy-time, frequency, polarization, spatial-frequency, and polarization-frequency [1] have been proposed using specific FWM processes in different optical fibers.

Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC)•Jun 23, 2025•0 citations

Optical fiber polarization-entangled photon pair source using intermodal spontaneous four-wave mixing in the visible spectral band

K Lee, Jae‐Sun Jung, J H Lee

Abstract The theoretical and experimental investigation results of the generation of the polarization-entangled photon pairs operating at visible wavelengths are reported. The generation of polarization-entangled photon pairs was based on intermodal spontaneous four-wave mixing (IM-SFWM) using standard step-index few-mode fiber. It was shown theoretically that several combinations of IM-SFWM processes could occur depending on spatial modes of a pump beam. A polarization-entangled photon pair source based on Sagnac loop incorporating a segment of few-mode fiber were then experimentally created. A two-photon interference fringe visibility of our implemented photon pair source were 91.7% and 88.8% in H/V bases and D/A bases, respectively. A quantum state tomography was also conducted to reconstruct the density matrix of the generated state with a fidelity to a maximum entangled state of 93.1%.

Laser Physics Letters•Dec 13, 2022•4 citations

Progress toward photon-pair efficiency optimization using four-wave mixing in few-mode fibers

Seyedehnajmeh Montazeri, Mina Esmaeelpour

Intermodal four-wave mixing (FWM) process in few-mode fibers (FMFs) could be utilized for entangled photon-pair generation. Previous studies mainly performed in single-mode fibers suffered from the significant Raman scattering background from the glass fiber. Therefore, the instantaneous Raman and FWM effects would compete; this could be avoided in FMFs if the modal dispersion is larger than the Raman gain spectra. Utilizing two pumps in different modes in FMFs will generate photon pairs in various modes. Here, we study the effect of pump spectral separation on the intermodal FWM power and bandwidth using a seeding technique. It is concluded that the further the pumps and intermodal FWM idler and signal are from each other spectrally, the smaller the photon efficiency and larger the bandwidth. Experimental results for two FMFs of different differential mode group delay values are presented.

Applied Optics•Apr 7, 2025•1 citation

Polarization-entangled photon pairs in the visible spectral band using intermodal spontaneous four-wave mixing

Ju Han Lee, Kyungtaek Lee, Junha Jung

Abstract The theoretical and experimental investigation results of the generation of the polarization-entangled photon pairs operating at visible wavelengths are reported. The generation of polarization-entangled photon pairs was based on intermodal spontaneous four-wave mixing (IM-SFWM) using standard step-index few-mode fiber. It was shown theoretically that several combinations of IM-SFWM processes could occur depending on spatial modes of a pump beam. A polarization-entangled photon pair source based on Sagnac loop incorporating a segment of few-mode fiber were then experimentally created. A two-photon interference fringe visibility of our implemented photon pair source were 91.7% and 88.8% in H/V bases and D/A bases, respectively. A quantum state tomography was also conducted to reconstruct the density matrix of the generated state with a fidelity to a maximum entangled state of 93.1%.

•Mar 29, 2022•0 citations

Photon-pair generation by intermodal spontaneous four-wave mixing in birefringent, weakly guiding optical fibers

Karina Garay-Palmett, Daniel Cruz-Delgado, Francisco A. Domínguez-Serna +5 more

We present a theoretical and experimental study of the generation of photon pairs through the process of spontaneous four-wave mixing (SFWM) in a few-mode, birefringent fiber. Under these conditions, multiple SFWM processes are in fact possible, each associated with a different combination of transverse modes for the four waves involved. We show that in the weakly guiding regime, for which the propagation modes may be well approximated by linearly polarized modes, the departure from circular symmetry due to the fiber birefringence translates into conservation rules, which retain elements from azimuthal and rectangular symmetries: both OAM and parity must be conserved for a process to be viable. We have implemented a SFWM source based on a bowtie birefringent fiber, and have measured for a collection of pump wavelengths the SFWM spectra of each of the signal and idler photons in coincidence with its partner photon. We have used this information, together with knowledge of the transverse modes into which the signal and idler photons are emitted, as input for a genetic algorithm, which accomplishes two tasks: (i) the identification of the particular SFWM processes that are present in the source, and (ii) the characterization of the fiber used.

arXiv:1605.05426•Physical Review A•Mar 7, 2016•40 citations
Optical fiber-based sources of photon pairs with hybrid entanglement across multiple degrees of freedom are essential for a wide range of quantum technologies, while remaining compatible with existing communication networks. In this paper, we use a birefringent few-mode fiber to demonstrate an intermodal-vectorial four-wave mixing process that generates two pairs of spectrally overlapping signal-idler bands. Using phase-matching conditions, we show that the pairs of bands become spectrally indistinguishable when the group refractive indices of the signal and idler modes intersect at the pump wavelength. Our theoretical predictions are confirmed through experimental observations and corroborated by numerical simulations. Furthermore, we introduce the two-photon state associated with the overlapping bands, which simultaneously exhibits entanglement in a single degree of freedom and hybrid entanglement across multiple degrees of freedom. We also explain how the type and degree of entanglement can be controlled by tailoring the spectral overlap between the signal-idler bands. This study presents a promising scheme for a fiber-based source of photon pairs with entanglement spanning the spatial, polarization, and frequency degrees of freedom.
In this paper, we use a birefringent few-mode fiber to demonstrate an intermodal-vectorial four-wave mixing process that generates two pairs of spectrally overlapping signal-idler bands. Using phase-matching conditions, we show that the pairs of bands become spectrally indistinguishable when the group refractive indices of the signal and idler modes intersect at the pump wavelength. Our theoretical predictions are confirmed through experimental observations corroborated by numerical simulations. Furthermore, we introduce the two-photon state associated with the overlapping bands, which exhibits hybrid entanglement in spatial-polarization-frequency degrees of freedom. We explain that its degree of entanglement can be manipulated by tailoring the spectral position of the overlapping pairs of bands with respect to the Raman band and varying the excitation ratio of the pump modes. This study introduces a scheme for a fiber-based source of photon pairs with spatial-polarization-frequency entanglement.
Abstract The theoretical and experimental investigation results of the generation of the polarization-entangled photon pairs operating at visible wavelengths are reported. The generation of polarization-entangled photon pairs was based on intermodal spontaneous four-wave mixing (IM-SFWM) using standard step-index few-mode fiber. It was shown theoretically that several combinations of IM-SFWM processes could occur depending on spatial modes of a pump beam. A polarization-entangled photon pair source based on Sagnac loop incorporating a segment of few-mode fiber were then experimentally created. A two-photon interference fringe visibility of our implemented photon pair source were 91.7% and 88.8% in H/V bases and D/A bases, respectively. A quantum state tomography was also conducted to reconstruct the density matrix of the generated state with a fidelity to a maximum entangled state of 93.1%.
Intermodal four-wave mixing (FWM) process in few-mode fibers (FMFs) could be utilized for entangled photon-pair generation. Previous studies mainly performed in single-mode fibers suffered from the significant Raman scattering background from the glass fiber. Therefore, the instantaneous Raman and FWM effects would compete; this could be avoided in FMFs if the modal dispersion is larger than the Raman gain spectra. Utilizing two pumps in different modes in FMFs will generate photon pairs in various modes. Here, we study the effect of pump spectral separation on the intermodal FWM power and bandwidth using a seeding technique. It is concluded that the further the pumps and intermodal FWM idler and signal are from each other spectrally, the smaller the photon efficiency and larger the bandwidth. Experimental results for two FMFs of different differential mode group delay values are presented.
Abstract The theoretical and experimental investigation results of the generation of the polarization-entangled photon pairs operating at visible wavelengths are reported. The generation of polarization-entangled photon pairs was based on intermodal spontaneous four-wave mixing (IM-SFWM) using standard step-index few-mode fiber. It was shown theoretically that several combinations of IM-SFWM processes could occur depending on spatial modes of a pump beam. A polarization-entangled photon pair source based on Sagnac loop incorporating a segment of few-mode fiber were then experimentally created. A two-photon interference fringe visibility of our implemented photon pair source were 91.7% and 88.8% in H/V bases and D/A bases, respectively. A quantum state tomography was also conducted to reconstruct the density matrix of the generated state with a fidelity to a maximum entangled state of 93.1%.
We present a theoretical and experimental study of the generation of photon pairs through the process of spontaneous four-wave mixing (SFWM) in a few-mode, birefringent fiber. Under these conditions, multiple SFWM processes are in fact possible, each associated with a different combination of transverse modes for the four waves involved. We show that in the weakly guiding regime, for which the propagation modes may be well approximated by linearly polarized modes, the departure from circular symmetry due to the fiber birefringence translates into conservation rules, which retain elements from azimuthal and rectangular symmetries: both OAM and parity must be conserved for a process to be viable. We have implemented a SFWM source based on a bowtie birefringent fiber, and have measured for a collection of pump wavelengths the SFWM spectra of each of the signal and idler photons in coincidence with its partner photon. We have used this information, together with knowledge of the transverse modes into which the signal and idler photons are emitted, as input for a genetic algorithm, which accomplishes two tasks: (i) the identification of the particular SFWM processes that are present in the source, and (ii) the characterization of the fiber used.