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Advanced Quantum Technologies

A Rack‐Integrated and Modular GaAs Quantum Dot Source of Highly Entangled Photon Pairs

Yared G. Zena, Moritz Langer, Ahmad Rahimi, Sai Abhishikth Dhurjati, Pavel Ruchka, Sara Jakovljevic, Mandira Pal, Frank H. P. Fitzek, Harald W. Giessen, Jürgen W. Czarske, Riccardo Bassoli, Caspar Hopfmann

Published Oct 1, 2026• 0 citations
Publisher

Abstract

ABSTRACT Entangled photon pair sources are a key enabling technology for quantum communication and networking, yet their deployment beyond laboratory environments is hindered by system‐level complexity, limited operational stability, and insufficient industry compatibility. Here, we demonstrate a rack‐based, mobile quantum light source architecture based on a semiconductor quantum dot emitter that directly addresses these challenges through modular system integration and automated quantum state verification. The source generates polarization‐entangled photon pairs with an entanglement negativity of up to , confirming near‐maximal entanglement quality. In continuous, hands‐off operation over a 6 h time window, the system achieves an average combined exciton and biexciton single‐photon count rate of kHz and a maximum rate of kHz, while maintaining a of more than 95%. These results are enabled by the integration of optical excitation, collection, cryogenic operation, and control electronics within a standardized rack footprint, together with automated monitoring. By demonstrating simultaneously high entanglement quality, sustained brightness over a 6 h period, and inherent architectural robustness in an industry‐aligned system, this work advances semiconductor quantum dot devices toward deployable entangled photon sources for applied quantum photonics.

DOI
10.1002/qute.70510

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ABSTRACT Entangled photon pair sources are a key enabling technology for quantum communication and networking, yet their deployment beyond laboratory environments is hindered by system‐level complexity, limited operational stability, and insufficient industry compatibility. Here, we demonstrate a rack‐based, mobile quantum light source architecture based on a semiconductor quantum dot emitter that directly addresses these challenges through modular system integration and automated quantum state verification. The source generates polarization‐entangled photon pairs with an entanglement negativity of up to , confirming near‐maximal entanglement quality. In continuous, hands‐off operation over a 6 h time window, the system achieves an average combined exciton and biexciton single‐photon count rate of kHz and a maximum rate of kHz, while maintaining a of more than 95%. These results are enabled by the integration of optical excitation, collection, cryogenic operation, and control electronics within a standardized rack footprint, together with automated monitoring. By demonstrating simultaneously high entanglement quality, sustained brightness over a 6 h period, and inherent architectural robustness in an industry‐aligned system, this work advances semiconductor quantum dot devices toward deployable entangled photon sources for applied quantum photonics.
Entangled photon pair sources are a key enabling technology for quantum communication and networking, yet their deployment beyond laboratory environments is hindered by system-level complexity, limited operational stability, and insufficient industry compatibility. Here, we demonstrate a rack-based, mobile quantum light source architecture based on a semiconductor quantum dot emitter that directly addresses these challenges through modular system integration and automated operation. The source generates polarization-entangled photon pairs with an entanglement negativity 2n of up to 0.98(1)0.98(1)0.98(1), confirming near-maximal entanglement quality. In continuous, hands-off operation over a six-hour time window, the system achieves an average single-photon emission rate of 697(8)697(8)697(8) kHz and a maximum rate of 740(7)740(7)740(7) kHz, while maintaining 2n-value of more than 959595 %\%%. These results are enabled by the integration of optical excitation, collection, cryogenic operation, and control electronics within a standardized rack footprint, together with automated monitoring. By demonstrating simultaneously high entanglement quality, sustained brightness, and long-term operational stability in an industry-aligned system architecture, this work advances semiconductor quantum dot sources toward deployable entangled photon sources for applied quantum photonics.
Semiconductor quantum dots (QDs) have emerged as a premier solid-state platform for the deterministic generation of nonclassical light, offering a compelling pathway toward scalable quantum photonic systems. While single-photon emission from QDs has reached a high level of maturity, the realization of high-fidelity entangled photon-pair sources remains an active and rapidly evolving frontier. In this review, we survey the recent progress in QD-based entangled photon sources, highlighting the conceptual evolution from the established biexciton-exciton cascade to the emerging paradigm of spontaneous two-photon emission. We further examine how advances in nanophotonic architectures and coherent control strategies are redefining fundamental performance limits, enabling concurrent improvements in source brightness, coherence, and entanglement fidelity. Finally, we discuss the key physical and technological challenges that must be addressed to bridge the gap between laboratory demonstrations and large-scale deployment. We conclude by outlining the future opportunities for integrating QD-based entangled photon sources into practical quantum communication, computation, and sensing platforms.
For quantum light sources in everyday telecommunication networks, quantum science needs to be fully transformed into quantum technology. The first necessary step to move outside a well-controlled lab environment requires the use of quantum light sources operating in the technologically relevant telecom O- and C-band. This can be provided using epitaxial quantum dots as deterministic sources of quantum light. Particularly intriguing is that emitters operating at telecom wavelengths are rapidly catching up with their short wavelength counterparts in terms of performances. Here, we make a decisive step forward in the development of quantum communication networks: a state-of-the-art source of quantum light, a semiconductor quantum dot (QD), with record coincidence rate for entangled photon emission in the telecom C-band, is operated inside an optimized rack-based setup. This setup includes a tunable pulsed laser for the QD excitation (from quasi- to fully resonant excitation), all optics for the excitation filtering, and QD signal coupling into single-mode fibers. Overall, the setup allows for above 50%50\%50% transmission for both exciton and biexciton photons. These results show that quantum dots-based telecom light sources can now be transported and integrated into existing fiber infrastructures, an important step to demonstrate the feasibility of the upcoming quantum internet.
Semiconductor quantum dots (QDs) have emerged as a premier solid-state platform for the deterministic generation of nonclassical light, offering a compelling pathway toward scalable quantum photonic systems. While single-photon emission from QDs has reached a high level of maturity, the realization of high-fidelity entangled photon-pair sources remains an active and rapidly evolving frontier. In this review, we survey the recent progress in QD-based entangled photon sources, highlighting the conceptual evolution from the established biexciton–exciton cascade to the emerging paradigm of spontaneous two-photon emission. We further examine how advances in nanophotonic architectures and coherent control strategies are redefining fundamental performance limits, enabling concurrent improvements in source brightness, coherence, and entanglement fidelity. Finally, we discuss the key physical and technological challenges that must be addressed to bridge the gap between laboratory demonstrations and large-scale deployment. We conclude by outlining the future opportunities for integrating QD-based entangled photon sources into practical quantum communication, computation, and sensing platforms.
We demonstrate an ultra-compact source of on-demand, maximally entangled photon pairs using single GaAs quantum dots embedded in monolithic microlenses coupled to a lensed single-mode fiber. A 3D-printed micro-objective with a numerical aperture of 0.6 enables efficient fiber coupling and near-diffraction-limited performance with 604(16) nm resolution directly in the cryogenic environment at 3.8 K. The system achieves high single-photon emission rates [392(20) kHz] and purities [99.2(5)%] using two-photon resonant excitation. Leveraging the exciton–biexciton cascade, it produces near-maximally entangled photon pairs with peak entanglement negativities of 2n = 0.96 ± 0.02. The presented quantum light source combines state-of-the-art performance and long-term stability with a dramatically reduced system footprint, making it well-suited for seamless industrial integration.
ABSTRACT Many protocols of future quantum networks rely on the availability of entangled qubits which enable links among remote nodes due to their unique properties. Therefore, the efficient generation of entangled photons constitutes a key goal toward the implementation of such quantum networks. However, currently available sources are bound by intrinsic limitations, as for instance probabilistic nature of emission. Deterministic quantum emitters pose a potential solution for this issue, however, the maturity of their device platforms still needs to be improved for truly on‐demand emission. While record efficiencies are currently found at near‐infrared wavelengths, sources at telecommunication wavelengths will likely be the ideal choice for quantum networks. That motivates the development of efficient sources of entangled photons in the telecom regime. This work addresses that challenge presenting a telecom C‐band source of polarization entangled photons based on semiconductor quantum dots incorporated in a planar cavity structure. In this way, triggered emission of entangled photon pairs with a coincidence rate of (biexciton/exciton fiber‐coupled single‐photon count rates of /) combined with values of / is achieved. Full quantum state tomography of the two‐photon state demonstrates simultaneously entanglement fidelities of up to to the Bell state.