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Continuous-variable quantum key distribution protocol using coherent states and heterodyne detection, called No-Switching protocol, is widely used in practical systems due to the simple experimental setup without basis switching and easy…

Quantum Physics · Physics 2024-02-02 Jiale Mi , Yiming Bian , Lu Fan , Song Yu , Yichen Zhang

Continuous-variable quantum key distribution (CVQKD) using coherent states and heterodyne detection enables secure quantum communication based on technology that has large similarities to coherent optical telecommunication. Yet, practical…

Quantum key distribution (QKD) enables two remote parties to share encryption keys with security based on the laws of physics. Continuous variable (CV) QKD with coherent states and coherent detection integrates well with existing…

Quantum key distribution (QKD) provides means for unconditional secure key transmission between two distant parties. However, in practical implementations, it suffers from quantum hacking due to device imperfections. Here we propose a…

Quantum Physics · Physics 2014-07-16 Shi-Hai Sun , Mu-Sheng Jiang , Xiang-Chun Ma , Chun-Yan Li , Lin-Mei Liang

We give a description of balanced homodyne detection (BHD) using a conventional laser as a local oscillator (LO), where the laser field outside the cavity is a mixed state whose phase is completely unknown. Our description is based on the…

Quantum Physics · Physics 2007-05-23 Mikio Fujii

Imperfect devices in commercial quantum key distribution systems open security loopholes that an eavesdropper may exploit. An example of one such imperfection is the wavelength dependent coupling ratio of the fiber beam splitter. Utilizing…

The security proofs of continuous-variable quantum key distribution are based on the assumptions that the eavesdropper can neither act on the local oscillator nor control Bob's beam splitter. These assumptions may be invalid in practice due…

Continuous-variable measurement-independent-device quantum key distribution (CV-MDI-QKD) can offer high secure key rate at metropolitan distance and remove all side channel loopholes of detection as well. However, there is no complete…

Quantum Physics · Physics 2019-01-11 Hua-Lei Yin , Wei Zhu , Yao Fu

In continuous-variable quantum key distribution (CVQKD) systems, using a local local oscillator (LLO) scheme removes the local oscillator side channel, enhances Bob's detection performance and reduces the excess noise caused by photon…

Quantum Physics · Physics 2025-10-01 Yi Zheng , Jiarui Wu , Chenlei Fang , Qingbing Ji , Wei Pan , Haobin Shi

A significant performance inhibitor of free-space continuous variable quantum key distribution (CVQKD) is turbulence, which gives rise to wavefront phase and amplitude aberrations. We demonstrate that in a turbulent channel, during coherent…

We demonstrate a contradiction of quantum mechanics with local hidden variable theories for continuous variable quadrature phase amplitude (``position'' and ``momentum'') measurements, by way of a violation of a Bell inequality. For any…

Quantum Physics · Physics 2019-08-17 A. Gilchrist , P. Deuar , M. D. Reid

We propose an improved two-way continuous-variable quantum key distribution (CV QKD) protocol by adding proper random noise on the receiver's homodyne detection, the security of which is analysed against general collective attacks. The…

Quantum Physics · Physics 2013-05-07 Maozhu Sun , Xiang Peng , Hong Guo

We propose a simplified measurement scheme for a Gaussian modulated coherent state (GMCS) protocol for continuous variable quantum key distribution (CV-QKD), utilizing homodyne detection without quadrature switching. The reference frame of…

Quantum Physics · Physics 2025-11-13 Vinod N. Rao , Emma Tien Hwai Medlock , Timothy Spiller , Rupesh Kumar

Most quantum key distribution (QKD) protocols can be classified as either a discrete-variable (DV) protocol or continuous-variable (CV) protocol, based on how classical information is being encoded. We propose a protocol that combines the…

Continuous-variable measurement-device-independent quantum key distribution (CV-MDI QKD) can address vulnerabilities on the detection side of a QKD system. The core of this protocol involves continuous-variable Bell measurements performed…

Quantum Physics · Physics 2025-12-19 Yanhao Sun , Ziyang Chen , Xiangyu Wang , Song Yu , Hong Guo

Although multiple-input multiple-output (MIMO) terahertz (THz) continuous-variable quantum key distribution (CVQKD) is theoretically secure, practical vulnerabilities may arise due to detector imperfections. This paper explores a CV…

Quantum Physics · Physics 2025-11-10 Leixin Wu , Congtian Deng , Jiayu Pan , Lingtao Zhang , Yanyan Feng , Runbo Zhao , Yang Shen , Yuying Zhang , Jian Zhou

Quantum key distribution, which ensures information-theoretically secret key generation, is currently advancing through photonic integration to achieve high performance, cost reduction and compact size, thereby facilitating the large-scale…

Quantum Physics · Physics 2024-02-19 Yiming Bian , Yan Pan , Xuesong Xu , Liang Zhao , Yang Li , Wei Huang , Lei Zhang , Song Yu , Yichen Zhang , Bingjie Xu

When undertaking continuous-variable quantum key distribution (CV-QKD) across atmospheric channels, strong classical local oscillators (LOs) are often polarization-multiplexed with the weak quantum signals for coherent measurement at the…

Continuous-Variable Quantum Key Distribution (CV-QKD) relies on accurate noise calibration at the receiver to ensure the security of quantum communication. Traditional calibration methods often oversimplify noise characteristics, neglecting…

Quantum Physics · Physics 2025-09-10 Guillaume Ricard , Yves Jaouën , Romain Alléaume

Quantum key distribution (QKD) allows two users to exchange a provably secure key for cryptographic applications. In prepare-and-measure QKD protocols, the states must be indistinguishable to prevent information leakage to an eavesdropper…