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

Quantum Computing, Communication, and Simulation

Frequency-comb-assisted, broadband optical phase stabilization for quantum communications

Daehyun Ahn, Jabir M. V., Ivan A. Burenkov, Sergey Vladimirovich Polyakov

Published Mar 19, 2025• 0 citations
Publisher

Abstract

To study channel-to-channel phase drift in broadband links, we implement a dense wavelength-division multiplexing (DWDM)-based phase stabilization testbed. We systematically study phase stabilization in adjacent DWDM channels of metropolitan-scale fiber links. A 25GHz frequency comb with a sub-Hz laser generated two DWDM-separable frequency components at 1550.12 nm and 1549.32 nm as signal and reference channels. One of these components is stabilized using a phase-locked-loop circuit, while the phase noise in the other channel is monitored. We demonstrate a significantly reduced phase noise in the monitored channel over a 100 km link. This approach mitigates phase noise in wavelength-detuned long-distance network links while wavelength-separating the classical probing signal and reducing its impact on the quantum channel through Raman scattering in a long fiber.

DOI
10.1117/12.3042076

Related papers

Robust phase stabilization of a dark quantum channel over a 120 km deployed fiber link

D. Ahn, Ivan A. Burenkov, M. V. Jabir +5 more

Establishing phase-stable links over long-distance fiber infrastructure is crucial for phase-sensitive networking protocols. Faint-light and quantum networking present an additional challenge of keeping the payload channel dark. In this work, we present a scalable solution for phase stabilization of dark metropolitan-scale fiber links using wavelength-division-multiplexing (WDM). We implement a combined feed-back and feed-forward phase stabilization for a target channel by combining error signals from two separate reference channels over a 120 km deployed aerial fiber link. Residual phase noise in the dark target channel is reduced by two orders of magnitude compared to a WDM feedback-only strategy and reaches subfemtosecond root-mean-square (RMS) values. Observed cross-talk photon noise is ≈500 photons per second. Potentially, several dark target channels can be phase-stabilized without injecting additional reference channels. This solution is a major step toward scalable metropolitan-distance quantum networking applications, including single-rail entanglement distribution, quantum key distribution, coherent clock transfer, and coherent optical communication.

Optica•Feb 24, 2026•0 citations

Long-term phase stabilization for metropolitan-scale dark quantum channels

D. Ahn, Ivan A. Burenkov, M. V. Jabir +5 more

We employ a frequency comb to demonstrate a multiband wavelength-division-multiplexing (WDM)-based phase stabilization over a metropolitan-scale fiber link while maintaining a dark quantum channel. We achieve phase stability over 100 seconds, a four orders of magnitude improvement of the current state of the art.

•Jan 1, 2026•0 citations

Enabling phase stabilization of quantum networks via displacement-enhanced photon counting

M. V. Jabir, Daehyun Ahn, N. Fajar R. Annafianto +3 more

Optical phase stabilization, tracking, and locking in long fiber links are pivotal for the functionality of many communication protocols and distributed sensors. However, conventional phase stabilization methods use strong optical probe signals that may contaminate and destroy fragile quantum signals propagating in the same fiber link. Here, we experimentally demonstrate phase locking of fiber spools up to 100 km and over 120 km deployed optical communication link using faint coherent states with an average of just photons per second detected at the receiving detector as a probe signal. The power spectral density of phase noise, integrated from 1 Hz to 50 kHz, yields an excess rms phase noise of 110 mrad (corresponding to timing jitter below 0.09 fs) for a 100 km fiber spool and 140 mrad (corresponding to rms timing jitter below 0.12 fs) for deployed fiber. The displacement-enhanced measurement protocol that we employ for phase stabilization yields Fisher information that is greater than that of homodyne and heterodyne measurement protocols for fiber links longer than 100 m and, therefore, exceeds the canonical shot noise limit of accuracy. By implementing this stabilization strategy with a 50% duty cycle, we enable time-division multiplexed faint light and quantum payloads to coexist within the same communication channel.

Optica•Mar 21, 2025•8 citations

Exponential speedup of polarization stabilization for long distance DWDM quantum networks

Jinyi Du, En Teng Lim, Xingjian Zhang +4 more

Fibre-based quantum networks distributing polarization entanglement require a stable and uninterrupted transmission basis for reliable operation. Bright classical reference light enables rapid polarization feedback but can introduce noise into quantum channels. Entangled-photon-based feedback avoids this noise, but typically interrupts the target entanglement channel during calibration and becomes prohibitively slow over long distances due to the product loss of fibre links. Here, we overcome both limitations by combining wavelength-bracketed probing with switch-enabled path decomposition. Spectrally adjacent entangled-photon sidebands track the polarization response of the central distribution channel without interrupting its transmission, while optical switches and local reference fibres independently determine the signal and idler network transformations. Transferring the resulting compensation settings to the central channel eliminates calibration-induced downtime and changes the acquisition-time scaling from the product of the link losses to the sum of losses. We demonstrate the method on a 133 km fibre testbed and achieve continuous closed-loop stabilization for more than 24 hours without classical reference light. The decomposition of multi-link quantum feedback into single-link measurements provides a scalable stabilization strategy for wavelength-multiplexed quantum networks.

quant-pharXiv:2609.02841•Sep 3, 2026•0 citations

Long-distance frequency transfer over an urban fiber link using optical phase stabilization

Haifeng Jiang, F. Kéfélian, S. G. Crane +8 more

We transferred the frequency of an ultrastable laser over 86 km of urban fiber. The link is composed of two cascaded 43 km fibers connecting two laboratories, Laboratoire National de Métrologie et d'Essais-Systèmes de Référence Temps-Espace (LNE-SYRTE) and Laboratoire de Physique des Lasers (LPL), in the Paris area. In an effort to realistically demonstrate a link of 172 km without using spooled fiber extensions, we implemented a recirculation loop to double the length of the urban fiber link. The link is fed with a 1542 nm cavity-stabilized fiber laser having a sub-Hz linewidth. The fiber-induced phase noise is measured and cancelled with an all fiber-based interferometer using commercial off-the-shelf pigtailed telecommunication components. The compensated link shows an Allan deviation of a few 10−16 at one second and a few 10−19 at 10,000 seconds.

arXiv:0807.1882•Journal of the Optical Society of America B•Nov 18, 2008•166 citations

1 × N DWDM channel selective quantum frequency conversion

Tomoaki Arizono, Toshiki Kobayashi, Shigehito Miki +5 more

Dense wavelength division multiplexing (DWDM) is a key technology for realizing high-capacity and flexible quantum communication networks. To enable the emerging quantum internet, quantum frequency conversion is also essential for bridging different quantum systems over optical fiber networks. In this work, aiming at a frequency-multiplexed quantum internet, we present a channel-selective quantum frequency conversion (CS-QFC) based on difference frequency generation in a PPLN waveguide, which has been widely used in conventional QFC experiments. The CS-QFC converts a frequency of a photon at a single frequency to any frequency in the DWDM channels by dynamically selecting one of the pump lights. In the experiment, we demonstrated the CS-QFC from 780 nm to around 1540 nm employing one of the pump lights around 1580 nm detuned with a spacing of 25 GHz. From the experiment using the laser light, we showed that the output-frequency tunability of our CS-QFC reaches 2.5 THz, which corresponds to the ability to establish a 100-ch DWDM dynamic link from a single quantum system. Using photon pairs, we performed an experiment in which photons were routed into seven of the DWDM channels. As a result, photons were converted to the channels corresponding to the pump frequencies, while keeping the nonclassical cross-correlation functions, and no crosstalk to the other channels was observed.

arXiv:2409.08025•Optics Express•Dec 19, 2025•3 citations
To study channel-to-channel phase drift in broadband links, we implement a dense wavelength-division multiplexing (DWDM)-based phase stabilization testbed. We systematically study phase stabilization in adjacent DWDM channels of metropolitan-scale fiber links. A 25GHz frequency comb with a sub-Hz laser generated two DWDM-separable frequency components at 1550.12 nm and 1549.32 nm as signal and reference channels. One of these components is stabilized using a phase-locked-loop circuit, while the phase noise in the other channel is monitored. We demonstrate a significantly reduced phase noise in the monitored channel over a 100 km link. This approach mitigates phase noise in wavelength-detuned long-distance network links while wavelength-separating the classical probing signal and reducing its impact on the quantum channel through Raman scattering in a long fiber.
Establishing phase-stable links over long-distance fiber infrastructure is crucial for phase-sensitive networking protocols. Faint-light and quantum networking present an additional challenge of keeping the payload channel dark. In this work, we present a scalable solution for phase stabilization of dark metropolitan-scale fiber links using wavelength-division-multiplexing (WDM). We implement a combined feed-back and feed-forward phase stabilization for a target channel by combining error signals from two separate reference channels over a 120 km deployed aerial fiber link. Residual phase noise in the dark target channel is reduced by two orders of magnitude compared to a WDM feedback-only strategy and reaches subfemtosecond root-mean-square (RMS) values. Observed cross-talk photon noise is ≈500 photons per second. Potentially, several dark target channels can be phase-stabilized without injecting additional reference channels. This solution is a major step toward scalable metropolitan-distance quantum networking applications, including single-rail entanglement distribution, quantum key distribution, coherent clock transfer, and coherent optical communication.
Optical phase stabilization, tracking, and locking in long fiber links are pivotal for the functionality of many communication protocols and distributed sensors. However, conventional phase stabilization methods use strong optical probe signals that may contaminate and destroy fragile quantum signals propagating in the same fiber link. Here, we experimentally demonstrate phase locking of fiber spools up to 100 km and over 120 km deployed optical communication link using faint coherent states with an average of just photons per second detected at the receiving detector as a probe signal. The power spectral density of phase noise, integrated from 1 Hz to 50 kHz, yields an excess rms phase noise of 110 mrad (corresponding to timing jitter below 0.09 fs) for a 100 km fiber spool and 140 mrad (corresponding to rms timing jitter below 0.12 fs) for deployed fiber. The displacement-enhanced measurement protocol that we employ for phase stabilization yields Fisher information that is greater than that of homodyne and heterodyne measurement protocols for fiber links longer than 100 m and, therefore, exceeds the canonical shot noise limit of accuracy. By implementing this stabilization strategy with a 50% duty cycle, we enable time-division multiplexed faint light and quantum payloads to coexist within the same communication channel.
Fibre-based quantum networks distributing polarization entanglement require a stable and uninterrupted transmission basis for reliable operation. Bright classical reference light enables rapid polarization feedback but can introduce noise into quantum channels. Entangled-photon-based feedback avoids this noise, but typically interrupts the target entanglement channel during calibration and becomes prohibitively slow over long distances due to the product loss of fibre links. Here, we overcome both limitations by combining wavelength-bracketed probing with switch-enabled path decomposition. Spectrally adjacent entangled-photon sidebands track the polarization response of the central distribution channel without interrupting its transmission, while optical switches and local reference fibres independently determine the signal and idler network transformations. Transferring the resulting compensation settings to the central channel eliminates calibration-induced downtime and changes the acquisition-time scaling from the product of the link losses to the sum of losses. We demonstrate the method on a 133 km fibre testbed and achieve continuous closed-loop stabilization for more than 24 hours without classical reference light. The decomposition of multi-link quantum feedback into single-link measurements provides a scalable stabilization strategy for wavelength-multiplexed quantum networks.
We transferred the frequency of an ultrastable laser over 86 km of urban fiber. The link is composed of two cascaded 43 km fibers connecting two laboratories, Laboratoire National de Métrologie et d'Essais-Systèmes de Référence Temps-Espace (LNE-SYRTE) and Laboratoire de Physique des Lasers (LPL), in the Paris area. In an effort to realistically demonstrate a link of 172 km without using spooled fiber extensions, we implemented a recirculation loop to double the length of the urban fiber link. The link is fed with a 1542 nm cavity-stabilized fiber laser having a sub-Hz linewidth. The fiber-induced phase noise is measured and cancelled with an all fiber-based interferometer using commercial off-the-shelf pigtailed telecommunication components. The compensated link shows an Allan deviation of a few 10−16 at one second and a few 10−19 at 10,000 seconds.
Dense wavelength division multiplexing (DWDM) is a key technology for realizing high-capacity and flexible quantum communication networks. To enable the emerging quantum internet, quantum frequency conversion is also essential for bridging different quantum systems over optical fiber networks. In this work, aiming at a frequency-multiplexed quantum internet, we present a channel-selective quantum frequency conversion (CS-QFC) based on difference frequency generation in a PPLN waveguide, which has been widely used in conventional QFC experiments. The CS-QFC converts a frequency of a photon at a single frequency to any frequency in the DWDM channels by dynamically selecting one of the pump lights. In the experiment, we demonstrated the CS-QFC from 780 nm to around 1540 nm employing one of the pump lights around 1580 nm detuned with a spacing of 25 GHz. From the experiment using the laser light, we showed that the output-frequency tunability of our CS-QFC reaches 2.5 THz, which corresponds to the ability to establish a 100-ch DWDM dynamic link from a single quantum system. Using photon pairs, we performed an experiment in which photons were routed into seven of the DWDM channels. As a result, photons were converted to the channels corresponding to the pump frequencies, while keeping the nonclassical cross-correlation functions, and no crosstalk to the other channels was observed.