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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

Intensity modulation/direct detection (IM/DD) optical key distribution (OKD) is a method to generate a secret key whose security against passive eavesdropping is guaranteed by the shot noise inherent to the photodetection process. Here the…

Quantum Physics · Physics 2025-03-19 M. Jarzyna , M. Jachura , K. Banaszek

In this study, we analyze the secret key capacity of intensity modulation/direct detection optical key distribution (IM/DD OKD) for a free-space optical (FSO) link between a low-Earth orbit satellite and an optical ground station. Focusing…

A new and simple quantum key distribution scheme based on the quantum intensity correlation of optical twin beams and the directly local measurements of intensity noise of single optical beam is presented and experimentally demonstrated.…

Quantum Physics · Physics 2007-05-23 Xiaojun Jia , Xiaolong Su , Qing Pan , Kunchi Peng , Changde Xie

We investigate theoretically the efficiency of deep-space optical communication in the presence of background noise. With decreasing average signal power spectral density, a scaling gap opens up between optimized simple-decoded pulse…

Quantum Physics · Physics 2018-02-20 Marcin Jarzyna , Wojciech Zwoliński , Michał Jachura , Konrad Banaszek

Quantum key distribution (QKD) offers information-theoretic security based on the fundamental laws of physics. However, device imperfections, such as those in active modulators, may introduce side-channel leakage, thus compromising…

Quantum Physics · Physics 2023-05-10 Chengqiu Hu , Wenyuan Wang , Kai-Sum Chan , Zhenghan Yuan , Hoi-Kwong Lo

The role of squeezing in quantum key distribution with continuous variables based on homodyne detection and post-selection is investigated for several specific eavesdropping strategies. It is shown that amplitude squeezing creates strong…

Quantum Physics · Physics 2015-06-26 Peter Horak

The decoy state protocol has been considered to be one of the most important methods to protect the security of quantum key distribution (QKD) with a weak coherent source. Here we test two experimental approaches to generating the decoy…

Quantum Physics · Physics 2018-09-18 Anqi Huang , Shi-Hai Sun , Zhihong Liu , Vadim Makarov

Research on optimal eavesdropping models under practical conditions will help to evaluate realistic risk when employing quantum key distribution (QKD) system for secure information transmission. Intuitively, fiber loss will lead to the…

Quantum Physics · Physics 2024-01-01 Sheng Liu , Lu Fan , Zhengyu Li , Qiang Zhou , Yunbo Li , Dong Wang , Dechao Zhang , Yichen Zhang , Han Li

The local oscillator in practical continuous-variable quantum key distribution system fluctuates at any time during the key distribution process, which may open security loopholes for the eavesdropper to hide her eavesdropping behaviors.…

Quantum Physics · Physics 2023-08-02 Lu Fan , Yiming Bian , Mingze Wu , Yichen Zhang , Song Yu

We consider a continuous-variable (CV) quantum key distribution (QKD) protocol over free-space channels, which is simpler and more robust than typical CV QKD protocols. It uses a bright laser, squeezed and modulated in the amplitude…

Quantum Physics · Physics 2022-03-14 Nedasadat Hosseinidehaj , Matthew S. Winnel , Timothy C. Ralph

Based on the detection loophole-free photon key distribution (PKD) compatible with classical optical systems, an optical key distribution (OKD) protocol is presented for unconditionally secured cryptography in fiber-optic communications…

Quantum Physics · Physics 2018-11-22 Byoung S. Ham

Discrete-modulated continuous-variable quantum key distribution offers a pragmatic solution, greatly simplifying experimental procedures while retaining robust integration with classical optical communication. Theoretical analyses have…

Quantum Physics · Physics 2024-07-31 Mingze Wu , Junhui Li , Bingjie Xu , Song Yu , Yichen Zhang

We present a discretely modulated continuous-variable quantum key distribution system in free space by using strong coherent states. The amplitude noise in the laser source is suppressed to the shot-noise limit by using a mode cleaner…

Quantum Physics · Physics 2015-05-18 Yong Shen , Hongxin Zou , Liang Tian , Pingxing Chen , Jianmin Yuan

The decoy-state method is a prominent approach to enhance the performance of quantum key distribution (QKD) systems that operate with weak coherent laser sources. Due to the limited transmissivity of single photons in optical fiber, current…

Quantum Physics · Physics 2026-05-04 Daniil Trefilov , Xoel Sixto , Víctor Zapatero , Anqi Huang , Marcos Curty , Vadim Makarov

Quantum key distribution (QKD) enables the establishment of secret keys between users connected via a channel vulnerable to eavesdropping, with information-theoretic security, that is, independently of the power of a malevolent party. QKD…

Information-theoretic secret-key agreement is perhaps the most practically feasible mechanism that provides unconditional security at the physical layer to date. In this paper, we consider the problem of secret-key agreement by sharing…

We analyze the performance of on-off keying (OOK) and its restricted version pulse position modulation (PPM) over a lossy narrowband optical channel under the constraint of a low average photon number, when direct detection is used at the…

Quantum Physics · Physics 2015-02-05 Marcin Jarzyna , Piotr Kuszaj , Konrad Banaszek

We study how the imperfection of intensity modulator effects on the security of a practical quantum key distribution system. The extinction ratio of the realistic intensity modulator is considered in our security analysis. We show that the…

Quantum Physics · Physics 2012-07-04 Jing-Zheng Huang , Zhen-Qiang Yin , Shuang Wang , Hong-Wei Li , Wei Chen , Zheng-Fu Han

This paper considers secrecy enhancement mechanisms in visible light communication (VLC) systems with spatially distributed passive eavesdroppers (EDs) under the assumption that there are multiple LED transmitters and one legitimate…

Information Theory · Computer Science 2017-07-24 Sunghwan Cho , Gaojie Chen , Justin P. Coon
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