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:2606.21874

Demonstration of a Monolithic and Fully Telecom-Fiber-Compatible Tunable Source of Polarization Entangled Photon Pairs Based on a van der Waals Material

Benjamin Laudert, Fatemeh Abtahi, Duk Choi, Dragomir Neshev, Falk Eilenberger

quant-phSubmitted Jun 20, 2026• Announced Jun 23, 2026• 0 citations
arXivHTMLPDF

Abstract

We present a tunable, single-mode-optical-fiber-based source of polarization entangled photon pairs for the near-infrared telecommunication band that is deployable in standard infrastructure. The photon pairs are generated via spontaneous parametric down-conversion (SPDC) in a submicron-scale thin film of the inversion-broken rhombohedral polytype of the transition metal dichalcogenide molybdenum disulfide (3R-MoS$_2$), located between two fiber connectors. By exploiting the intrinsic symmetries of the second-order nonlinear susceptibility tensor of 3R-MoS$_2$, this hybrid approach offers control over the generated two-photon polarization state through the incident pump polarization. Most notably, two of the four maximally entangled Bell states, as well as fully co-polarized pairs can be produced. This represents a substantial improvement in terms of tunability and simplicity over established fiber-integrated sources, which require additional optical elements, precise alignment, or careful engineering of design parameters. Additionally, a nonlinear drop in the background photoluminescence signal of 3R-MoS$_2$ is observed at low pump powers, allowing us to reach a coincidences-to-accidentals ratio (CAR) of $(8.3\pm1.8)\times10^{3}$, the highest value recorded for SPDC in van der Waals materials to date.

Comments
20 pages, 10 figures

Related papers

Entangled Telecom Photon Generation using Twisted Van der Waals Crystals

Nidhin Prasannan, Konstantinos Mourzidis, Vishwas Jindal +11 more

Nanoscale quantum light sources are essential building blocks for integrated quantum photonic systems. Here, we report a wavelength-scale entangled-photon source based on van der Waals-engineered NbOBr$_2$, and benchmark its performance for telecom-wavelength quantum light generation. By exploiting the material's second-order nonlinearity, we generate quantum-correlated photon pairs via spontaneous parametric down-conversion. We then use a 90$^{\circ}$ twisted stacking to induce quantum interference in photon-pair generation, yielding polarization-entangled photons. This approach enables tunability of the quantum optical state via control of the excitation laser polarization. We experimentally obtain entanglement fidelities exceeding 95% for Bell states, along with a high coincidence-to-accidental ratio of $\sim$335, and a brightness approximately one order of magnitude higher than recently reported telecom sources based on transition metal dichalcogenide (TMD) 2D materials. These results establish twisted van der Waals engineering as a powerful platform for highly tunable, high-brightness quantum light sources at telecom wavelengths.

physics.opticsCross-listedarXiv:2605.14592•May 15, 2026•0 citations

Polarization-entangled photon-pair source with van der Waals 3R-WS2 crystal

Jiangang Feng, Yunkun Wu, Ruihuan Duan +7 more

Abstract Ultracompact entangled photon sources are pivotal to miniaturized quantum photonic devices. Van der Waals (vdW) nonlinear crystals promise efficient photon-pair generation and on-chip monolithic integration with nanophotonic circuitry. However, it remains challenging to generate maximally entangled Bell states of photon pairs with high purity, generation rate, and fidelity required for practical applications. Here, we realize a polarization-entangled photon-pair source based on spontaneous parametric down conversion in an ultrathin rhombohedral tungsten disulfide (3R-WS 2 ) crystal. This vdW entangled photonic source exhibits a high photon-pair purity with a coincidence-to-accidental ratio of above 800, a generation rate of 31 Hz, and two maximally polarization-entangled Bell states with fidelities exceeding 0.93 and entanglement degree over 0.97. These results stem from scalable optical nonlinearity, enhanced second-order susceptibility by electronic transitions, and a well-defined symmetry-enabled selection rule inherent in 3R-WS 2 . Our polarization entangled photon source can be integrated with photonic structures for generating more complex entangled states, thus paving an avenue for advanced quantum photonic systems toward computation and metrology.

eLight•Aug 23, 2024•44 citations

Generation of Tunable Entanglement from Thin-Film Lithium Niobate

Saniya Shinde, Maximilian A. Weissflog, Shaun Lung +7 more

Entangled photon pairs play a major role in various modern technologies such as quantum imaging, communication, and computing. Conventional photon-pair sources are often based on spontaneous parametric down-conversion in bulk nonlinear crystals. Recent advances have also shown entangled photon-pairs from transition metal dichalcogenide thin-films, however, these materials are not widely available and are not compatible with existing fabrication capabilities. We present a new thin-film lithium niobate source of polarization-entangled photon pairs at the telecom wavelength that requires no additional optical elements for entanglement generation and allows for easy application using the existing lithium niobate fabrication technologies. We demonstrate tunable entanglement generation using the three-fold rotational crystal symmetry of lithium niobate, allowing the generation of different maximally entangled Bell states or completely separable states depending on the polarization of the pump beam.

quant-pharXiv:2605.00214•May 4, 2026•0 citations

Entangled Telecom Photons Generation Using Twisted van der Waals Crystals

Nidhin Prasannan, Konstantinos Mourzidis, Vishwas Jindal +11 more

Nanoscale quantum light sources are essential building blocks for integrated quantum photonic systems. Here, we report a wavelength-scale entangled-photon source based on van der Waals-engineered NbOBr2 and benchmark its performance for telecom-wavelength quantum light generation. By exploiting the material's second-order nonlinearity, we generate quantum-correlated photon pairs via spontaneous parametric down-conversion. We then use a 90° twisted stacking to induce quantum interference in photon-pair generation, yielding polarization-entangled photons. This approach enables tunability of the quantum optical state via control of the excitation laser polarization. We experimentally obtain entanglement fidelities exceeding 95% for Bell states, along with a high coincidence-to-accidental ratio of ∼335 and a brightness approximately 1 order of magnitude higher than recently reported telecom sources based on transition metal dichalcogenide two-dimensional materials. These results establish twisted van der Waals engineering as a powerful platform for highly tunable, high-brightness quantum light sources at telecom wavelengths.

Nano Letters•Aug 18, 2026•0 citations

Spontaneous Parametric Down-Conversion in Transition Metal Dichalcogenides

Maximilian A. Weissflog, Anna N. Fedotova, Yilin Tang +10 more

Transition metal dichalcogenides (TMDCs) thinned-down to the monolayer level allow the realisation of very broad-band, phase-matching free nonlinear devices. A particularly interesting application would be the generation of entangled photon-pairs, which form the backbone of many recent implementations in quantum optics. However, the limited absolute efficiency of monolayers has so far only allowed seeded parametric amplification [1], experimental evidence for the generation of entangled photon-pairs through spontaneous parametric down-conversion (SPDC) remained elusive up to now [2]. A promising route for the realization of broad-band photon-pair sources in van der Waals materials are moderately thicker, yet still phase-matching free layer stacks with preserved noncentrosymmetry [3], [4]. Here, we close the gap of a missing entangled photon-pair source in TMDCs and demonstrate, for the first time to our knowledge, pair generation via SPDC in 3R-MoS2.

Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC)•Jun 26, 2023•0 citations

Polarization-Entangled Photon-Pair Sources Based on 3R-MoS2

Maximilian A. Weissflog, Anna N. Fedotova, Yilin Tang +16 more

We demonstrate for the first time generation of polarization-entangled photon-pairs in a transition metal dichalcogenide. Using 3R-phase molybdenum disulfide, we experimentally show tunable, high-fidelity generation of different polarization Bell states.

•Jan 1, 2024•0 citations
We present a tunable, single-mode-optical-fiber-based source of polarization entangled photon pairs for the near-infrared telecommunication band that is deployable in standard infrastructure. The photon pairs are generated via spontaneous parametric down-conversion (SPDC) in a submicron-scale thin film of the inversion-broken rhombohedral polytype of the transition metal dichalcogenide molybdenum disulfide (3R-MoS2_22​), located between two fiber connectors. By exploiting the intrinsic symmetries of the second-order nonlinear susceptibility tensor of 3R-MoS2_22​, this hybrid approach offers control over the generated two-photon polarization state through the incident pump polarization. Most notably, two of the four maximally entangled Bell states, as well as fully co-polarized pairs can be produced. This represents a substantial improvement in terms of tunability and simplicity over established fiber-integrated sources, which require additional optical elements, precise alignment, or careful engineering of design parameters. Additionally, a nonlinear drop in the background photoluminescence signal of 3R-MoS2_22​ is observed at low pump powers, allowing us to reach a coincidences-to-accidentals ratio (CAR) of (8.3±1.8)×103(8.3\pm1.8)\times10^{3}(8.3±1.8)×103, the highest value recorded for SPDC in van der Waals materials to date.
Nanoscale quantum light sources are essential building blocks for integrated quantum photonic systems. Here, we report a wavelength-scale entangled-photon source based on van der Waals-engineered NbOBr2_22​, and benchmark its performance for telecom-wavelength quantum light generation. By exploiting the material's second-order nonlinearity, we generate quantum-correlated photon pairs via spontaneous parametric down-conversion. We then use a 90∘^{\circ}∘ twisted stacking to induce quantum interference in photon-pair generation, yielding polarization-entangled photons. This approach enables tunability of the quantum optical state via control of the excitation laser polarization. We experimentally obtain entanglement fidelities exceeding 95% for Bell states, along with a high coincidence-to-accidental ratio of $\sim$335, and a brightness approximately one order of magnitude higher than recently reported telecom sources based on transition metal dichalcogenide (TMD) 2D materials. These results establish twisted van der Waals engineering as a powerful platform for highly tunable, high-brightness quantum light sources at telecom wavelengths.
Abstract Ultracompact entangled photon sources are pivotal to miniaturized quantum photonic devices. Van der Waals (vdW) nonlinear crystals promise efficient photon-pair generation and on-chip monolithic integration with nanophotonic circuitry. However, it remains challenging to generate maximally entangled Bell states of photon pairs with high purity, generation rate, and fidelity required for practical applications. Here, we realize a polarization-entangled photon-pair source based on spontaneous parametric down conversion in an ultrathin rhombohedral tungsten disulfide (3R-WS 2 ) crystal. This vdW entangled photonic source exhibits a high photon-pair purity with a coincidence-to-accidental ratio of above 800, a generation rate of 31 Hz, and two maximally polarization-entangled Bell states with fidelities exceeding 0.93 and entanglement degree over 0.97. These results stem from scalable optical nonlinearity, enhanced second-order susceptibility by electronic transitions, and a well-defined symmetry-enabled selection rule inherent in 3R-WS 2 . Our polarization entangled photon source can be integrated with photonic structures for generating more complex entangled states, thus paving an avenue for advanced quantum photonic systems toward computation and metrology.
Entangled photon pairs play a major role in various modern technologies such as quantum imaging, communication, and computing. Conventional photon-pair sources are often based on spontaneous parametric down-conversion in bulk nonlinear crystals. Recent advances have also shown entangled photon-pairs from transition metal dichalcogenide thin-films, however, these materials are not widely available and are not compatible with existing fabrication capabilities. We present a new thin-film lithium niobate source of polarization-entangled photon pairs at the telecom wavelength that requires no additional optical elements for entanglement generation and allows for easy application using the existing lithium niobate fabrication technologies. We demonstrate tunable entanglement generation using the three-fold rotational crystal symmetry of lithium niobate, allowing the generation of different maximally entangled Bell states or completely separable states depending on the polarization of the pump beam.
Nanoscale quantum light sources are essential building blocks for integrated quantum photonic systems. Here, we report a wavelength-scale entangled-photon source based on van der Waals-engineered NbOBr2 and benchmark its performance for telecom-wavelength quantum light generation. By exploiting the material's second-order nonlinearity, we generate quantum-correlated photon pairs via spontaneous parametric down-conversion. We then use a 90° twisted stacking to induce quantum interference in photon-pair generation, yielding polarization-entangled photons. This approach enables tunability of the quantum optical state via control of the excitation laser polarization. We experimentally obtain entanglement fidelities exceeding 95% for Bell states, along with a high coincidence-to-accidental ratio of ∼335 and a brightness approximately 1 order of magnitude higher than recently reported telecom sources based on transition metal dichalcogenide two-dimensional materials. These results establish twisted van der Waals engineering as a powerful platform for highly tunable, high-brightness quantum light sources at telecom wavelengths.
Transition metal dichalcogenides (TMDCs) thinned-down to the monolayer level allow the realisation of very broad-band, phase-matching free nonlinear devices. A particularly interesting application would be the generation of entangled photon-pairs, which form the backbone of many recent implementations in quantum optics. However, the limited absolute efficiency of monolayers has so far only allowed seeded parametric amplification [1], experimental evidence for the generation of entangled photon-pairs through spontaneous parametric down-conversion (SPDC) remained elusive up to now [2]. A promising route for the realization of broad-band photon-pair sources in van der Waals materials are moderately thicker, yet still phase-matching free layer stacks with preserved noncentrosymmetry [3], [4]. Here, we close the gap of a missing entangled photon-pair source in TMDCs and demonstrate, for the first time to our knowledge, pair generation via SPDC in 3R-MoS2.