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Integrated nonlinear light sources for quantum networks: a machine learning-enabled design

I. P. De Simeone, G. Maltese, Valentin Cambier, J.-P. Likforman, M. Ravaro, Luca Guidoni, F. Baboux, S. Ducci

Published May 28, 2026• 0 citations
Publisher

Abstract

We present the design of two photonic devices based on multilayer AlGaAs waveguides. The first is an ion-photon interface waveguide microcavity to entangle telecom photons with trapped Sr+ ions. The second device is a Bragg Reflection Waveguide generating broadband entangled photon pairs for scalable, multi-user entanglement distribution. Both designs were carried out using machine learning-enabled inverse design techniques

DOI
10.1117/12.3106259

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We present the design of two photonic devices based on multilayer AlGaAs waveguides. The first is an ion-photon interface waveguide microcavity to entangle telecom photons with trapped Sr+ ions. The second device is a Bragg Reflection Waveguide generating broadband entangled photon pairs for scalable, multi-user entanglement distribution. Both designs were carried out using machine learning-enabled inverse design techniques
The realization of a scalable quantum internet requires efficient light-matter interfaces that map stationary qubits onto photonic carriers for long-distance transmission. A central challenge is the generation of entangled photons simultaneously compatible with single-emitter transitions and low-loss telecom fiber infrastructure. Spontaneous parametric down-conversion in integrated photonic platforms offers a promising route toward this goal. Among available material systems, AlGaAs is particularly attractive due to its large second-order nonlinearity and strong potential for monolithic integration. However, engineering the spectral and spatial properties of the generated quantum states requires the simultaneous optimization of numerous geometric and material parameters, a task remaining computationally demanding for conventional numerical approaches. To address this challenge and enable rapid and high-fidelity modeling of complex nonlinear photonic devices, we develop an inverse-design framework based on neural network surrogate models. Using this readily extendable method, we design a transversely pumped AlGaAs waveguide microcavity that produces polarization-entangled photon pairs in distinct spatial modes and frequency channels, one at 1092 nm, resonant with a 88Sr+^{88}\text{Sr}^{+}88Sr+ transition, and the other at 1550 nm in the telecom C-band. This device establishes a direct photonic interface between trapped-ion qubits and long-haul fiber networks, providing a scalable pathway toward hybrid quantum network architectures.
Hybrid photonic devices represent a promising solution to the effective on-chip integration of all the components required for the generation, manipulation and detection of non-classical states of light encoding quantum information. We present an AlGaAs source of highly entangled photon pairs envisioned for the hybridization with silicon-on-insulator integrated platforms, in order to take benefit from the strong second order nonlinearity and the compliance with electrical pumping of the III-V platform and the maturity and CMOS compatibility of silicon photonic circuitry, enabling a wide variety of quantum information applications.
Integrated photonics is playing a key role in the development of quantum technologies covering applications ranging from quantum communication to computing and from simulations to sensing. In this context, material platforms enabling the chip-scale integration of quantum components are a key issue on the way towards real-world and large-scale technological implementations. In this paper, we review our last achievements on AlGaAs Bragg reflection waveguides emitting nonclassical states of light by spontaneous parametric down conversion. The choice of this platform combines the advantages of a mature fabrication technology, room temperature operation, emission in the telecom C-Band and compliance with electrical injection. We demonstrate the ability of these devices to generate a large variety of quantum states spanning from biphoton frequency combs to broadband polarization entanglement enabling promising applications in quantum processing as well as flexible quantum networks.
Entanglement represents a fundamental resource for quantum technologies, including quantum communication tasks. In this context, photons are the ideal physical systems due to their capability of carrying information over long distances. Hence, it is fundamental to design reliable sources of entangled photons in the telecom wavelength regime (around 1.55 μm), where optical fiber losses are low. In this paper we review different platforms used to generate telecom entangled photon pairs, and we focus in particular on an integrated source realized by the femtosecond laser writing (FLW) technique, which allows to devise stable and compact optical circuits in glass. We show how this technique can be employed to inscribe waveguides in nonlinear crystals for generation of telecom entangled photon pairs on a chip.
One of the key challenges for realizing large-scale quantum communication in installed fiber networks is to establish communication links between multiple users in a scalable and robust way. Quantum networks based on DWDM quantum correlation utilizing broadband entangled photon pair source could be the solution. Among many integrated photon source techniques, AlGaAs Bragg reflection waveguid (BRW), with its extremely high material χ(2) and negligible birefringence, can produce high brightness, wide bandwidth, post selection free polarization entangled photon pairs. In a scenario of entangled photon and classical light co-fiber transmitting, noise from the classical light could degrade the entanglement. In this paper. we designed and fabricated a Bragg reflection waveguide (BRW) AlGaAs/GaAs chip with high modal overlap to directly generate broadband polarization entanglement, and employed for demonstrate a fully connected three-user noisy network by multiplexing 3 pairings of DWMD channels, each pairing established a quantum communication link between any possible two users. Several causes of noise from chip fluorescence to co-fiber classical light, and their impacts on bit error rate (BER) were analyzed.