Engineering Quantum Links: Noise and Quantum-State-Degradation Metrics over Metropolitan Fiber Network
Abstract
Deploying quantum networks over existing network infrastructures requires the same engineering foundations that underpin classical communications: quantitative models of the channel's noise and of the impairments it imposes on the transmitted information. In this work, we build such a foundation on experimental measurements, grounding the quantum-network counterparts of the two cornerstone metrics of classical link characterization - namely, the SINR and the BER - on a 7.3 km deployed metropolitan-scale fiber-loop interconnecting two campuses of the University of Naples Federico II within the national QuantumInternet.it testbed. On the noise side, we adopt a photon-counting quantum analog of the SINR - in which dark counts constitute the intrinsic noise and the photons generated by classical traffic (through either spontaneous Raman scattering or inter-fiber crosstalk) constitute the interference - and we quantify each contribution directly on the deployed loop. On the bit-error side, we consider the main degrees-of-freedom available to encode a quantum state within an optical photon - namely, polarization, time, and frequency - and we quantify for each degree the channel-induced degradation and its drift over time. These results show that a quantum fiber link, like its classical counterpart, can be captured by a small set of measurable parameters, turning quantum networking over deployed fiber from a physics demonstration into an engineering design problem. Together, they provide the key ingredients of a quantum link budget for the Quantum Internet.
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BibTeX
@misc{caleffi2026engineering,
title = {{Engineering Quantum Links: Noise and Quantum-State-Degradation Metrics over Metropolitan Fiber Network}},
author = {Marcello Caleffi and Laura d'Avossa and Angela Sara Cacciapuoti},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.11359},
eprint = {2609.11359},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.11359},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Engineering Quantum Links: Noise and Quantum-State-Degradation Metrics over Metropolitan Fiber Network
AU - Marcello Caleffi
AU - Laura d'Avossa
AU - Angela Sara Cacciapuoti
PY - 2026
DA - 2026/09/10
PB - arXiv
DO - 10.48550/arxiv.2609.11359
UR - https://arxiv.org/abs/2609.11359
AB - Deploying quantum networks over existing network infrastructures requires the same engineering foundations that underpin classical communications: quantitative models of the channel's noise and of the impairments it imposes on the transmitted information. In this work, we build such a foundation on experimental measurements, grounding the quantum-network counterparts of the two cornerstone metrics of classical link characterization - namely, the SINR and the BER - on a 7.3 km deployed metropolitan-scale fiber-loop interconnecting two campuses of the University of Naples Federico II within the national QuantumInternet.it testbed. On the noise side, we adopt a photon-counting quantum analog of the SINR - in which dark counts constitute the intrinsic noise and the photons generated by classical traffic (through either spontaneous Raman scattering or inter-fiber crosstalk) constitute the interference - and we quantify each contribution directly on the deployed loop. On the bit-error side, we consider the main degrees-of-freedom available to encode a quantum state within an optical photon - namely, polarization, time, and frequency - and we quantify for each degree the channel-induced degradation and its drift over time. These results show that a quantum fiber link, like its classical counterpart, can be captured by a small set of measurable parameters, turning quantum networking over deployed fiber from a physics demonstration into an engineering design problem. Together, they provide the key ingredients of a quantum link budget for the Quantum Internet.
ER -