arXiv subjects

Mael Flament

Publications and source records attributed to Mael Flament.

12 recordsLinked to original sources

arXiv2026

Bichromatic Quantum Teleportation of Weak Coherent Polarization States on a Metropolitan Fiber

As quantum technologies mature, telecommunication operators have a clear opportunity to unlock and scale new services by providing the connectivity layer that links quantum computers, sensors, clocks, and other quantum devices. Realizing this opportunity requires demonstrating quantum networking protocols, including quantum teleportation, under real-world conditions on existing telecom infrastructure. In this work, we demonstrate quantum teleportation over Deutsche Telekom's metropolitan fiber testbed in Berlin using commercial components deployed at the telecom datacenter. A local Bell-state measurement between 795 nm photons from a weak coherent source and from a bichromatic warm-atom entangled photon source enables conditional state transfer onto an O-band photon, which is transmitted through a 30-km field-deployed fiber loop under real-world environmental conditions. The teleported state is reconstructed after propagation via state tomography, achieving an average teleportation fidelity of 90\% on the deployed link. System performance is evaluated in both the absence and the presence of co-propagating C-band classical traffic within the same fiber, demonstrating compatibility with wavelength-division multiplexed telecom infrastructure carrying live data channels.

quant-ph↗

arXiv2026

High-rate Scalable Entanglement Swapping Between Remote Entanglement Sources on Deployed New York City Fibers

Entanglement swapping between photon pairs generated at physically separated nodes over telecommunication fiber infrastructure is an essential step towards the quantum internet, enabling applications such as quantum repeaters, blind quantum computing, distributed quantum computing, and distributed quantum sensing. However, successful networked entanglement swapping relies on generating indistinguishable pairs of photons and preserving them over deployed fibers. This has limited most previous demonstrations to laboratory settings or relied on sophisticated methods to maintain the necessary indistinguishability. Here, we demonstrate a scalable entanglement swapping experiment using naturally indistinguishable entanglement sources based on warm atomic vapor cells. Without sharing lasers or optical frequency references between nodes, nor the need for pulsing the sources, we achieve a swapping rate of nearly 500 pairs/s while maintaining the CHSH parameter above 2. Additionally, we demonstrate the scalability of our method by maintaining the quality of the entanglement swapping on 17.6-km of deployed fibers in NYC, relying on commercially available SPADs at the spoke nodes, SNSPDs at the hub and standard time-synchronization techniques. Our work paves the way for the practical deployment of large-scale hub-and-spoke quantum networks within cities and data centers.

quant-ph↗

arXiv2026

Entanglement Distribution over a Polarization-Stabilized Aerial Fiber

We experimentally demonstrate the distribution of polarization-entangled photons across a 62-km, partially-aerial fiber. With polarization stabilization applied to the fiber link, we achieve a photon pair rate of approximately 1500 per second and observe a CHSH inequality violation with S=2.34.

quant-ph↗

arXiv2025

Hybrid Fiber-Free-Space Entanglement Distribution Using Off-the-Shelf Quantum Devices

Entanglement serves as a fundamental resource for quantum technologies, enabling communication and computation tasks that surpass classical limits. Its distribution across networks is essential for interconnecting quantum processors, enabling distributed quantum computing to address complex challenges in areas such as drug discovery, material science, and optimization. In this work, we report the successful distribution of polarization-entangled photon pairs across a campus-scale, three-node quantum network comprising both fiber and free-space optical links. The entire system was built using commercially available components provided by partners within the Netherlands Quantum Ecosystem. This result represents advancements in the technological maturity of quantum communication systems and demonstrates a pathway towards the practical deployment of early-stage quantum networks both on Earth and in space.

quant-ph↗

arXiv2025

High-Fidelity Quantum Entanglement Distribution in Metropolitan Fiber Networks with Co-propagating Classical Traffic

The Quantum Internet, a network of quantum-enabled infrastructure, represents the next frontier in telecommunications, promising capabilities that cannot be attained by classical counterparts. A crucial step in realizing such large-scale quantum networks is the integration of entanglement distribution within existing telecommunication infrastructure. Here, we demonstrate a real-world scalable quantum networking testbed deployed within Deutsche Telekom's metropolitan fibers in Berlin. Using commercially available quantum devices and standard add-drop multiplexing hardware, we distributed polarization-entangled photon pairs over dynamically selectable fiber paths ranging from 10~m to 60 km, and showed entanglement distribution over up to approximately 100~km. Quantum signals, transmitted at 1324~nm (O-band), coexist with conventional bidirectional C-band traffic without dedicated fibers or infrastructure changes. Active stabilization of the polarization enables robust long-term performance, achieving entanglement Bell-state fidelity bounds between 85-99% and Clauser-Horne-Shimony-Holt parameter $S$-values between 2.36-2.74 during continuous multiday operation. By achieving a high-fidelity entanglement distribution with less than 1.5% downtime, we confirm the feasibility of hybrid quantum-classical networks under real-world conditions at the metropolitan scale. These results establish deployment benchmarks and provide a practical roadmap for telecom operators to integrate quantum capabilities.

quant-ph↗

arXiv2025

High-fidelity entanglement between a telecom photon and a room-temperature quantum memory

Entanglement distribution through existing telecommunication infrastructure is crucial for realizing large-scale quantum networks. However, distance limitations imposed by photon losses and the no-cloning theorem present significant challenges. Quantum repeaters based on entangled telecom wavelength photons and quantum memories offer a promising solution to overcome these limitations. In this work, we report an important milestone in quantum repeater architecture by demonstrating entanglement between a telecom-wavelength (1324 nm) photon and a room-temperature quantum memory with a fidelity up to 90.2%, using simple rubidium systems for both photon generation and storage. Furthermore, we achieve high-rate photon-memory entanglement generation of up to 1,200 Bell pairs per second with 80% fidelity. The technical simplicity and robustness of our room-temperature systems paves the way towards deploying quantum networks at scale in realistic settings.

quant-ph↗

arXiv2024

Automated distribution of high-rate, high-fidelity polarization entangled photons using deployed metropolitan fibers

Distributing high-fidelity, high-rate entanglement over telecommunication infrastructure is one of the main paths towards large-scale quantum networks, enabling applications such as quantum encryption and network protection, blind quantum computing, distributed quantum computing, and distributed quantum sensing. However, the fragile nature of entangled photons operating in real-world fiber infrastructure has historically limited continuous operation of such networks. Here, we present a fully automated system capable of distributing polarization entangled photons over a 34 km deployed fiber in New York City. We achieve end-to-end pair rates of nearly $5\times10^5$ pairs/s and entanglement fidelity of approximately $99\%$. Separately, we achieve 15 days of continuous distribution, with a network up-time of $99.84\%$. Our work paves the way for practical deployment of 24/7 entanglement-based networks with rates and fidelity adequate for many current and future use-cases.

quant-ph↗

arXiv2023

High-rate sub-GHz linewidth bichromatic entanglement source for quantum networking

The generation of entangled photon pairs which are compatible with quantum devices and standard telecommunication channels are critical for the development of long range fiber quantum networks. Aside from wavelength, bandwidth matching and high fidelity of produced pairs are necessary for high interfacing efficiency. High-rate, robust entanglement sources that satisfy all these conditions remain an outstanding experimental challenge. In this work, we study an entanglement source based on four-wave mixing in a diamond configuration in a warm rubidium vapor. We theoretically and experimentally investigate a new operating regime and demonstrate an entanglement source which produces highly non-degenerate $795$ and $1324$-nm photon pairs. With this source we are able to achieve in-fiber entangled pair generation rates greater than $10^7\, /s$, orders of magnitude higher than previously reported atomic sources. Additionally, given our source's native compatibility with telecom infrastructure and atomic systems, it is an important step towards scalable quantum networks.

quant-ph↗

arXiv2022

Field-deployable Quantum Memory for Quantum Networking

High-performance quantum memories are an essential component for regulating temporal events in quantum networks. As a component in quantum-repeaters, they have the potential to support the distribution of entanglement beyond the physical limitations of fiber loss. This will enable key applications such as quantum key distribution, network-enhanced quantum sensing, and distributed quantum computing. Here, we present a quantum memory engineered to meet real-world deployment and scaling challenges. The memory technology utilizes a warm rubidium vapor as the storage medium, and operates at room temperature, without the need for vacuum- and/or cryogenic- support. We demonstrate performance specifications of high-fidelity retrieval (95\%) and low operation error $(10^{-2})$ at a storage time of 160 $μs$ for single-photon level quantum memory operations. We further show a substantially improved storage time (with classical-level light) of up to 1 ms by suppressing atomic diffusions. The device is housed in an enclosure with a standard 2U rackmount form factor, and can robustly operate on a day scale in a noisy environment. This result marks an important step toward implementing quantum networks in the field.

quant-ph↗

arXiv2018

Spatial characterization of photonic polarization entanglement using a Tpx3Cam intensified fast-camera

Scalable technologies to characterize the performance of quantum devices are crucial to creating large quantum networks and quantum processing units. Chief among the resources of quantum information processing is entanglement. Here we describe the full temporal and spatial characterization of polarization-entangled photons produced by Spontaneous Parametric Down Conversions using an intensified high-speed optical camera, Tpx3Cam. This novel technique allows for precise determination of Bell inequality parameters with minimal technical overhead, as well as novel characterization methods of the spatial distribution of entangled quantum information. This could lead to multiple applications in Quantum Information Science, opening new perspectives for the scalability of quantum experiments.

quant-ph↗

arXiv2018

Hong-Ou-Mandel interference of polarization qubits stored in independent room-temperature quantum memories

Quantum repeater networks require independent quantum memories capable of storing and retrieving indistinguishable photons to perform high-repetition entanglement swapping operations. The ability to perform these coherent operations at room temperature is of prime importance to the realization of scalable quantum networks. We perform Hong-Ou-Mandel (HOM) interference between photonic polarization qubits stored and retrieved from two sets of independent room-temperature quantum memories. We show a steady improvement in memory parameters and visibilities, culminating in a high quantum memory HOM visibility of 43%, compared to the 48% no-memory limit of our set-up. These results lay the groundwork for future applications using large-scale memory-assisted quantum networks.

quant-ph↗

arXiv2018

A large-diameter cryogenic rotation stage for half-wave plate polarization modulation on the POLARBEAR-2 experiment

We describe the design of a cryogenic rotation stage (CRS) for use with the cryogenic half-wave plate (CHWP) polarization modulator on the POLARBEAR-2b and POLARBEAR-2c (PB2b/c) cosmic microwave background (CMB) experiments, the second and third installments of the Simons Array. Rapid modulation of the CMB polarization signal using a CHWP suppresses 1/f contamination due to atmospheric turbulence and allows a single polarimeter to measure both polarization states, mitigating systematic effects that arise when differencing orthogonal detectors. To modulate the full detector array while avoiding excess photon loading due to thermal emission, the CHWP must have a clear-aperture diameter of > 450 mm and be cooled to < 100 K. We have designed a 454-mm-clear-aperture, < 65 K CRS using a superconducting magnetic bearing driven by a synchronous magnetic motor. We present the specifications for the CRS, its interfacing to the PB2b/c receiver cryostat, its performance in a stand-alone test, and plans for future work.

astro-ph.IM↗