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

Optical Fiber Communication Conference

Characterizing a Metropolitan Fiber Link with Heralded Single Photons from an Electronic-Photonic Chip

Anirudh Ramesh, Ely M. Eastman, Danielius Kramnik, Imbert Wang, Ðorđe Gluhović, Miloš A. Popović, Vladimir Marko Stojanovic, Prem Kumar

Published Jan 1, 2025• 1 citation
Publisher

Abstract

We characterize single photon transmission through a ~ 48 km underground fiber link. Using an integrated source, we measure delay variations in the timing correlations between the photon-pairs of 40 ps over 90 minutes, compared to 200 ps in a 50 km spool kept in the laboratory, showing the suitability of buried fiber for quantum networks.

DOI
10.1364/ofc.2025.th2a.61

Related papers

Robust Time Transfer with Single Photons on Hybrid Quantum Communication Scenarios in Fiber and Free-Space

Christopher Spiess, Karolina Pacicrek, Nico Döll +2 more

Quantum communication networks exploit single photons to generate secure encryption keys and can have very tight timing requirements [1]. These synchronization requirements are met through highly stable references, but there is ongoing research on using only single photons to enable synchronization [2]–[4]. The single photons come naturally with the quantum communication protocol and motivate its use for both data and time transfer. As point-to-point quantum communication scenarios rapidly expand to large networks, there is great demand for robust and resource-saving synchronization methods. In this contribution, we show that single photons can be indeed a solid carrier of timing information. We complement other publications [2], [5] by describing the performance of the synchronization approach and evaluating it on a 1.7 km free space and a 70 km deployed intercity fiber link. We demonstrate time deviations of 100 ps (1.7 km free-space link) and 174 ps (70 km fiber-link) at integration times of 1 second with only crystal oscillators, which is slightly larger than 54 ps in a lab environment (Fig. 1(a)). Our results provide advances towards a strong, independent, and secure quantum communication network without external hardware and a reliable operation under versatile link scenarios.

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

Integrated Sources of Photon-Pairs for Quantum Networking

Vijay Soorya Shunmuga Sundaram

Quantum networking enables the distribution of quantum information across distant nodes, unlocking capabilities such as secure communication, distributed quantum computing, enhanced metrology, and tests of fundamental physics. Photons serve as the natural carriers of quantum information over long distances due to their low loss in optical fibers and robustness to environmental decoherence. However, the practical realization of quantum networks remains limited by the lack of photon sources that are simultaneously compatible with diverse quantum systems, stable over long timescales, and suitable for deployment in real-world fiber infrastructure. This dissertation addresses these challenges through the co-development of photon-pair sources and a field-deployed quantum networking testbed. We present two complementary chip-scale sources of correlated photon pairs tailored for distinct bottlenecks in quantum networking. The first is a hybrid visible–telecom photon-pair source designed to address a fundamental spectral mismatch between quantum nodes and communication channels. While most quantum memories and processors operate at visible to near- nfrared wavelengths, optical fibers exhibit minimal loss in the telecommunications band. By integrating periodically poled nonlinear waveguides with photonic integrated circuits, we demonstrate a platform capable of directly generating visible–telecom photon pairs, enabling efficient interfacing between heterogeneous quantum systems and existing fiber networks. The second source is a fully packaged, broadband telecom photon-pair source based on silicon waveguide spirals, designed for stable, long-duration operation. This stability enables extended measurements necessary to overcome channel losses and environmental drifts in deployed fiber networks. These sources are evaluated within RoQNET (Rochester Quantum Network), a ∼20 km fiber link between the Rochester Institute of Technology and the University of Rochester. Using this platform, we demonstrate the transmission and on-chip modulation of heralded telecom single photons, verify their nonclassical statistics, and characterize long-term channel behavior. Additionally, we explore programmable time-bin entanglement distribution using spectral waveshapers, providing a flexible approach to quantum communication. Together, this work establishes a co-designed source–network framework for scalable, heterogeneous quantum networking.

•Jun 22, 2026•0 citations

Single-photon time-of-flight measurements for benchmarking time transfer in quantum networks

Dongxing He, Paulina S. Kuo, Ya-Shian Li-Baboud +4 more

We developed a single-photon time-of-flight measurement method to benchmark fiber-path-delay. The results suggest that augmenting existing optical two-way time and frequency transfer protocols could enhance the timing precision to sub-10 ps for metropolitan-scale quantum networks.

Journal of Optical Communications and Networking•Nov 14, 2025•0 citations

Demonstration of quantum network protocols over a 14-km urban fiber link

Stephan Kucera, Christian Haen, Elena Arenskötter +9 more

Abstract We report on the implementation of quantum entanglement distribution and quantum state teleportation over a 14.4 km urban dark-fiber link, which is partially underground, partially overhead, and patched in several stations. We characterize the link for its use as a quantum channel and realize its active polarization stabilization. Using a type-II cavity-enhanced SPDC photon pair source, a 40 Ca + single-ion quantum memory, and quantum frequency conversion to the telecom C-band, we demonstrate photon-photon entanglement, ion-photon entanglement, and teleportation of a qubit state from the ion onto a remote telecom photon, all realized over the urban fiber link.

npj Quantum Information•Sep 14, 2024•39 citations

Transmission of light–matter entanglement over a metropolitan network

Jelena V. Rakonjac, Samuele Grandi, Sören Wengerowsky +3 more

We report on the transmission of telecom photons entangled with a multimode solid-state quantum memory over a deployed optical fiber in a metropolitan area. Photon pairs were generated through spontaneous parametric downconversion, with one photon stored in a rare-earth-based quantum memory, and the other, at telecommunication wavelengths, traveling through increasing distances of optical fiber, first in the laboratory and then outside in a deployed fiber loop. We measured highly non-classical correlations between the stored and the telecom photons for storage times up to 25 µs and for a fiber separation up to 50 km. We also report light–matter entanglement with a two-qubit fidelity up to 88%, which remains constant within error bars for all fiber lengths, showing that the telecom qubit does not suffer decoherence during the transmission. Finally, we moved the detection stage of the telecom photons to a different location placed 16 km away, and confirmed the non-classical correlations between the two photons. Our system was adapted to provide the transmission of precise detection times and synchronization signals over long quantum communication channels, providing the first steps for a future quantum network involving quantum memories and non-classical states.

arXiv:2304.05416•Optica Quantum•Nov 16, 2023•26 citations

Demonstration of quantum network protocols over a 14-km urban fiber link

Stephan Kucera, Christian Haen, Elena Arenskötter +9 more

We report on the implementation of quantum entanglement distribution and quantum state teleportation over a 14.4-km urban dark-fiber link, which is partially underground, partially overhead, and patched in several stations. We characterize the link for its use as a quantum channel and realize its active polarization stabilization. Using a type-II cavity-enhanced SPDC photon pair source, a $^{40}$Ca$^{+}$ single-ion quantum memory, and quantum frequency conversion to the telecom C-band, we demonstrate photon-photon entanglement, ion-photon entanglement, and teleportation of a qubit state from the ion onto a remote telecom photon, all realized over the urban fiber link.

arXiv:2404.04958•Apr 7, 2024•0 citations
We characterize single photon transmission through a ~ 48 km underground fiber link. Using an integrated source, we measure delay variations in the timing correlations between the photon-pairs of 40 ps over 90 minutes, compared to 200 ps in a 50 km spool kept in the laboratory, showing the suitability of buried fiber for quantum networks.
Quantum communication networks exploit single photons to generate secure encryption keys and can have very tight timing requirements [1]. These synchronization requirements are met through highly stable references, but there is ongoing research on using only single photons to enable synchronization [2]–[4]. The single photons come naturally with the quantum communication protocol and motivate its use for both data and time transfer. As point-to-point quantum communication scenarios rapidly expand to large networks, there is great demand for robust and resource-saving synchronization methods. In this contribution, we show that single photons can be indeed a solid carrier of timing information. We complement other publications [2], [5] by describing the performance of the synchronization approach and evaluating it on a 1.7 km free space and a 70 km deployed intercity fiber link. We demonstrate time deviations of 100 ps (1.7 km free-space link) and 174 ps (70 km fiber-link) at integration times of 1 second with only crystal oscillators, which is slightly larger than 54 ps in a lab environment (Fig. 1(a)). Our results provide advances towards a strong, independent, and secure quantum communication network without external hardware and a reliable operation under versatile link scenarios.
Quantum networking enables the distribution of quantum information across distant nodes, unlocking capabilities such as secure communication, distributed quantum computing, enhanced metrology, and tests of fundamental physics. Photons serve as the natural carriers of quantum information over long distances due to their low loss in optical fibers and robustness to environmental decoherence. However, the practical realization of quantum networks remains limited by the lack of photon sources that are simultaneously compatible with diverse quantum systems, stable over long timescales, and suitable for deployment in real-world fiber infrastructure. This dissertation addresses these challenges through the co-development of photon-pair sources and a field-deployed quantum networking testbed. We present two complementary chip-scale sources of correlated photon pairs tailored for distinct bottlenecks in quantum networking. The first is a hybrid visible–telecom photon-pair source designed to address a fundamental spectral mismatch between quantum nodes and communication channels. While most quantum memories and processors operate at visible to near- nfrared wavelengths, optical fibers exhibit minimal loss in the telecommunications band. By integrating periodically poled nonlinear waveguides with photonic integrated circuits, we demonstrate a platform capable of directly generating visible–telecom photon pairs, enabling efficient interfacing between heterogeneous quantum systems and existing fiber networks. The second source is a fully packaged, broadband telecom photon-pair source based on silicon waveguide spirals, designed for stable, long-duration operation. This stability enables extended measurements necessary to overcome channel losses and environmental drifts in deployed fiber networks. These sources are evaluated within RoQNET (Rochester Quantum Network), a ∼20 km fiber link between the Rochester Institute of Technology and the University of Rochester. Using this platform, we demonstrate the transmission and on-chip modulation of heralded telecom single photons, verify their nonclassical statistics, and characterize long-term channel behavior. Additionally, we explore programmable time-bin entanglement distribution using spectral waveshapers, providing a flexible approach to quantum communication. Together, this work establishes a co-designed source–network framework for scalable, heterogeneous quantum networking.
Abstract We report on the implementation of quantum entanglement distribution and quantum state teleportation over a 14.4 km urban dark-fiber link, which is partially underground, partially overhead, and patched in several stations. We characterize the link for its use as a quantum channel and realize its active polarization stabilization. Using a type-II cavity-enhanced SPDC photon pair source, a 40 Ca + single-ion quantum memory, and quantum frequency conversion to the telecom C-band, we demonstrate photon-photon entanglement, ion-photon entanglement, and teleportation of a qubit state from the ion onto a remote telecom photon, all realized over the urban fiber link.
We report on the transmission of telecom photons entangled with a multimode solid-state quantum memory over a deployed optical fiber in a metropolitan area. Photon pairs were generated through spontaneous parametric downconversion, with one photon stored in a rare-earth-based quantum memory, and the other, at telecommunication wavelengths, traveling through increasing distances of optical fiber, first in the laboratory and then outside in a deployed fiber loop. We measured highly non-classical correlations between the stored and the telecom photons for storage times up to 25 µs and for a fiber separation up to 50 km. We also report light–matter entanglement with a two-qubit fidelity up to 88%, which remains constant within error bars for all fiber lengths, showing that the telecom qubit does not suffer decoherence during the transmission. Finally, we moved the detection stage of the telecom photons to a different location placed 16 km away, and confirmed the non-classical correlations between the two photons. Our system was adapted to provide the transmission of precise detection times and synchronization signals over long quantum communication channels, providing the first steps for a future quantum network involving quantum memories and non-classical states.
We report on the implementation of quantum entanglement distribution and quantum state teleportation over a 14.4-km urban dark-fiber link, which is partially underground, partially overhead, and patched in several stations. We characterize the link for its use as a quantum channel and realize its active polarization stabilization. Using a type-II cavity-enhanced SPDC photon pair source, a 40^{40}40Ca+^{+}+ single-ion quantum memory, and quantum frequency conversion to the telecom C-band, we demonstrate photon-photon entanglement, ion-photon entanglement, and teleportation of a qubit state from the ion onto a remote telecom photon, all realized over the urban fiber link.