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Quantum Key Distribution (QKD) provides information-theoretic security, but is limited by distance in optical networks, thereby requiring repeater nodes to extend coverage. Existing works usually assume all repeater nodes and associated Key…

Networking and Internet Architecture · Computer Science 2025-09-15 Arup Kumar Marik , Basabdatta Palit , Sadananda Behera

The emergence of quantum computing poses significant risks to the security of modern communication networks as it breaks today's public-key cryptographic algorithms. Quantum Key Distribution (QKD) offers a promising solution by harnessing…

Cryptography and Security · Computer Science 2026-02-23 Ali Al-kuwari , Noureldin Mohamed , Saif Al-kuwari , Ahmed Farouk , Bikash K. Behera

Single photon detector (SPD) has a maximum count rate due to its dead time, which results in that the dynamic range of photon counting optical time-domain reflectometry (PC-OTDR) de-creases with the length of monitored fiber. To further…

Instrumentation and Detectors · Physics 2020-01-08 Bin Li , Guangwei Deng , Ruiming Zhang , Zhonghua Ou , Heng Zhou , Yun Ling , Yunxiang Wang , You Wang , Kun Qiu , Haizhi Song , Qiang Zhou

Quantum key distribution (QKD) systems can send signals over more than 100 km standard optical fiber and are widely believed to be secure. Here, we show experimentally for the first time a technologically feasible attack, namely the…

Quantum Physics · Physics 2011-04-05 Yi Zhao , Chi-Hang Fred Fung , Bing Qi , Christine Chen , Hoi-Kwong Lo

In the maintenance of optical fiber networks, there is a growing demand for high-precision measurement of optical loss distribution and fault locations over long distances. In this study, we propose an OCDR method incorporating periodic…

Optical key distribution (OKD) protects the physical layer of communication links by taking advantage of the inherent noise present in the photodetection process. It allows for efficient generation of a shared random key between two distant…

Quantum Physics · Physics 2026-03-24 Karol Łukanowski , Michał Wójcik , Stefano Olivares , Konrad Banaszek , Marcin Jarzyna

We implement a photon-counting Optical Time Domain Reflectometer (OTDR) at 1.55um which exhibits a high 2-point resolution and a high accuracy. It is based on a low temporal-jitter photon-counting module at 1.55um. This detector is composed…

Quantum Physics · Physics 2009-11-13 Matthieu Legre , Rob Thew , Hugo Zbinden , Nicolas Gisin

Quantum key distribution (QKD) is a revolutionary cryptography response to the rapidly growing cyberattacks threat posed by quantum computing. Yet, the roadblock limiting the vast expanse of secure quantum communication is the exponential…

This study discusses key characteristics and limitations of time-domain reflectometry (TDR) systems based on the Hermitian symmetric orthogonal frequency-division multiplexing (HS-OFDM) scheme for power line sensing. In this sense, a system…

Signal Processing · Electrical Eng. & Systems 2019-01-25 Lucas Giroto de Oliveira , Mateus de L. Filomeno , Moisés V. Ribeiro

Photon counting optical time-domain reflectometry (PC-OTDR) based on the single photon detection is an effective scheme to attain the high spatial resolution for optical fiber fault monitoring. Currently, due to the spatial resolution of…

The twin-field class quantum key distribution (TF-class QKD) has experimentally demonstrated the ability to surpass the fundamental rate-distance limit without requiring a quantum repeater, as a revolutional milestone. In TF-class QKD…

Quantum Physics · Physics 2025-01-16 Qingquan Peng , Jiu-Peng Chen , Tianyi Xing , Dongyang Wang , Yizhi Wang , Yang Liu , Anqi Huang

We present $\phi$-OTDR for detecting and localising full spark-gap breakdowns by analysing backscattered light phase and frequency-domain signatures during high-voltage discharges synchronised with oscilloscope-recorded events. Measuring…

The fabrication of quantum key distribution (QKD) systems typically involves several parties, thus providing Eve with multiple opportunities to meddle with the devices. As a consequence, conventional hardware and/or software hacking attacks…

We describe the realization of a quantum key distribution (QKD) system clocked at 100 MHz. The system includes classical postprocessing implemented via software, and is operated over a 12 km standard telecommunication dark fiber in a…

Quantum Physics · Physics 2011-08-31 Xiaofan Mo , Itzel Lucio Martinez , Philip Chan , Chris Healey , Steve Hosier , Wolfgang Tittel

Shape tracking of medical devices using strain sensing properties in optical fibers has seen increased attention in recent years. In this paper, we propose a novel guidance system for intra-arterial procedures using a distributed strain…

Medical Physics · Physics 2017-07-24 Francois Parent , Maxime Gerard , Raman Kashyap , Samuel Kadoury

In this work, we present a reliable, efficient, and tight numerical method for calculating key rates for finite-dimensional quantum key distribution (QKD) protocols. We illustrate our approach by finding higher key rates than those…

Quantum Physics · Physics 2018-07-30 Adam Winick , Norbert Lütkenhaus , Patrick J. Coles

Time-energy high-dimensional quantum key distribution (HD-QKD) leverages the high-dimensional nature of time-energy entangled biphotons and the loss tolerance of single-photon detection to achieve long-distance key distribution with high…

Quantum Physics · Physics 2016-10-24 Murphy Yuezhen Niu , Feihu Xu , Fabian Furrer , Jeffrey H. Shapiro

A quantum key distribution system may be probed by an eavesdropper Eve by sending in bright light from the quantum channel and analyzing the back-reflections. We propose and experimentally demonstrate a setup for mounting such a…

Quantum Physics · Physics 2014-12-16 Nitin Jain , Elena Anisimova , Imran Khan , Vadim Makarov , Christoph Marquardt , Gerd Leuchs

We report on methods to monitor the transmission path in optical networks using a correlation-based OTDR technique with direct and coherent detection. A high probing symbol rate can provide picosecond-accuracy of the fiber propagation…

Signal Processing · Electrical Eng. & Systems 2023-06-07 Michael H. Eiselt , Florian Azendorf , Andre Sandmann , Florian Spinty , Mirko Lawin

Measurement-device-independent quantum key distribution (MDI-QKD) protocol has been demonstrated as a viable solution to detector side-channel attacks. One of the main advantages of MDI-QKD is that the security can be proved without making…

Quantum Physics · Physics 2015-04-14 Bing Qi