The Quantum Internet Research Group at the University of Naples Federico II will contribute to IEEE Quantum Week 2026 (QCE26) with an experimental study addressing a key challenge for the development of scalable quantum networks: the synchronization and interconnection of entanglement-based quantum nodes over real-world metropolitan fiber infrastructure.
Sunday, September 13
Research Paper Presentation
“Interconnection of Quantum Networks at Urban Scale: Analysis of Temporal Stability of Entangled Photon Sources”, presented by Laura d’Avossa.
Abstract — Time synchronization is a fundamental requirement in entanglement-based quantum networks, where the indistinguishability of photons in the time domain is essential for enabling Hong–Ou–Mandel interference and entanglement swapping. In addition to precise temporal alignment, it is equally crucial to ensure the stability of the reference clock over time, as even small fluctuations can degrade the overall performance of the network. In this work, we investigate the stability of clock synchronization for entanglement distribution based on entangled-photon sources operating in the telecommunication C-band. Temporal correlations between photon detection events are analyzed using time-tagged coincidence measurements, enabling the extraction of synchronization peaks and their long-term stability. Experimental results demonstrate that, once locked, the sources exhibit stable temporal correlations over an 8-hour acquisition period, with a maximum observed drift of approximately 120 ps, primarily associated with long fiber links. The width of the correlation peak remains consistent with detector jitter, indicating negligible additional system-induced temporal broadening. A central result of this work is the experimental synchronization between two entanglement-photon sources in a realistic metropolitan deployment, where entanglement distribution is performed over existing telecommunication infrastructure characterized by non-negligible losses and background noise. In this scenario, despite the presence of significant imperfections introduced by the metropolitan-scale fiber network, the observed correlations remain clearly detectable and are consistently well-approximated by Gaussian statistics. This confirms that the two sources can be reliably synchronized not only in controlled laboratory conditions but also under real-world operating constraints, where channel impairments and environmental fluctuations play a dominant role. Therefore, these results represent an initial step toward scalable quantum network architectures.
The work provides an experimental contribution to the broader Quantum Internet Research Group vision of developing scalable, quantum-native networking architectures capable of operating beyond controlled laboratory environments and over real-world communication infrastructure.
