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A highly attenuated laser pulse which gives a weak coherent state is widely used in quantum key distribution (QKD) experiments. A weak coherent state has multi-photon components, which opens up a security loophole to the sophisticated…

Quantum Physics · Physics 2008-08-12 Xiongfeng Ma

High-dimensional (HD) entanglement promises both enhanced key rates and overcoming obstacles faced by modern-day quantum communication. However, modern convex optimization-based security arguments are limited by computational constraints;…

Quantum Physics · Physics 2025-07-04 Florian Kanitschar , Marcus Huber

Quantum Key Distribution (QKD) guarantees the security of communication with quantum physics. Most of widely adopted QKD protocols currently encode the key information with binary signal format---qubit, such as the polarization states.…

Quantum Physics · Physics 2018-01-23 Fumin Wang , Pei Zeng , Xiaoli Wang , Hong Gao , Fuli Li , Pei Zhang

Quantum key distribution (QKD) provides secure keys resistant to code-breaking quantum computers. As headed towards commercial application, it is crucial to guarantee the practical security of QKD systems. However, the difficulty of…

Quantum Physics · Physics 2018-05-14 Zhengyu Li , Yi-Chen Zhang , Hong Guo

In a recent work by Maitra et al. (Phys. Rev. A, 2017), it was shown that the existing Quantum Private Query (QPQ) protocols fail to maintain the database security if the entangled states shared between Alice and Bob are not of a certain…

Quantum Physics · Physics 2017-05-15 Jyotirmoy Basak , Bappaditya Ghosh , Arpita Maitra , and Goutam Paul

High-dimensional entanglement is considered to hold great potential for quantum key distribution (QKD) in high-loss and -noise scenarios. To harness its robustness, we construct a source for high-dimensional time-bin entangled photons…

Rapid advancements in quantum computing and machine learning threaten the long-term security of classical blockchain systems, whose protection mechanisms largely rely on computational difficulties. In this study, we propose a quantum…

Quantum Physics · Physics 2025-12-24 Aktaş , Arzu , Yılmaz , İhsan

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

We present a linear optical scheme for error-free distribution of two-photon polarization entangled Bell states over noisy channels. The scheme can be applied to an elementary quantum repeater protocol with potentially significant…

Quantum Physics · Physics 2009-11-13 Demetrios Kalamidas

We introduce a novel time-frequency quantum key distribution (TFQKD) scheme based on photon pairs entangled in these two conjugate degrees of freedom. The scheme uses spectral detection and phase modulation to enable measurements in the…

Quantum Physics · Physics 2015-06-15 J. Nunn , L. Wright , C. Söller , L. Zhang , I. A. Walmsley , B. J. Smith

We present a protocol for deterministic and highly efficient quantum cryptography with entangled photon pairs in a 4x4-dimentional Hilbert space. Two communicating parties, Alice and Bob first share a both polarization- and path-entangled…

Quantum Physics · Physics 2007-05-23 Zhi Zhao , Tao Yang , Zeng-Bing Chen , Jiangfeng Du , Jian-Wei Pan

Quantum computing provides a feasible multi-layered security challenge to classical blockchain networks. Quantum blockchains that rely on quantum key distribution (QKD) to establish secure channels can address this feasible threat. Whereas,…

Quantum Physics · Physics 2026-05-12 Xuan Li , Yun Mao , Ying Guo

This paper presents a hybrid cryptographic protocol, using quantum and classical resources, for authentication and authorization in a network. One or more trusted servers distribute streams of entangled photons to individual resources that…

Quantum Physics · Physics 2007-05-23 D. R. Kuhn

We present a generalized tomographic quantum key distribution protocol in which the two parties share a Bell diagonal mixed state of two qubits. We show that if an eavesdropper performs a coherent measurement on many quantum ancilla states…

We investigate schemes for quantum secret sharing and quantum dense coding via tripartite entangled states. We present a scheme for sharing classical information via entanglement swapping using two tripartite entangled GHZ states. In order…

Quantum Physics · Physics 2009-11-11 Zheng-Yuan Xue , You-Min Yi , Zhuo-Liang Cao

We propose a scheme for encoding logical qubits in a subspace protected against collective rotations around the propagation axis using the polarization and transverse spatial degrees of freedom of single photons. This encoding allows for…

Quantum Physics · Physics 2009-11-13 L. Aolita , S. P. Walborn

We consider entanglement detection for quantum key distribution systems that use two signal states and continuous variable measurements. This problem can be formulated as a separability problem in a qubit-mode system. To verify…

Quantum Physics · Physics 2007-05-23 Johannes Rigas , Otfried Gühne , Norbert Lütkenhaus

We present a quantum key distribution protocol based on four-level particles entanglement. Furthermore, a controlled quantum key distribution protocol is proposed by utilizing three four-level particles. We show that the two protocols are…

Quantum Physics · Physics 2011-06-07 Tao Yan , Fengli Yan

Standard quantum key distribution (QKD) protocols typically assume that the distant parties share a common reference frame. In practice, however, establishing and maintaining a good alignment between distant observers is rarely a trivial…

Quantum Physics · Physics 2014-04-04 Joshua A. Slater , Cyril Branciard , Nicolas Brunner , Wolfgang Tittel

High-dimensional quantum key distribution (QKD) offers higher information capacity and stronger resilience to noise compared to its binary counterpart. However, these advantages are often hindered by the difficulty of realizing the required…

Quantum Physics · Physics 2025-04-04 Ohad Lib , Kfir Sulimany , Mateus Araújo , Michael Ben-Or , Yaron Bromberg