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Quantum key distribution (QKD) enables information-theoretic secure communication, yet its ultimate tolerance to noise and achievable transmission distance remain fundamentally constrained. We establish the maximum quantum bit error rate…

Quantum Physics · Physics 2026-02-27 Stefano Pirandola

Quantum-limited amplifiers increase the amplitude of quantum signals at the price of introducing additional noise. Quantum purification protocols operate in the reverse way, by reducing the noise while attenuating the signal. Here we…

Quantum Physics · Physics 2017-04-12 Xiaobin Zhao , Giulio Chiribella

A low-noise amplifier (LNA) amplifies a very low-power signal without significantly degrading its signal-to-noise ratio. This paper provides the design of a linear low noise amplifier with the transistor BFP 640 using bilateral approach…

Signal Processing · Electrical Eng. & Systems 2020-01-01 Puneeth Jubba Honnaiah , Shridhar Reddy

Quantum key distribution (QKD) based on coherent states is well known for its implementation simplicity, but it suffers from loss-dependent attacks based on optimal unambiguous state discrimination. Crucially, previous research has…

Quantum Physics · Physics 2020-06-05 Li Liu , Yukun Wang , Emilien Lavie , Arno Ricou , Chao Wang , Fen Zhuo Guo , Charles Ci Wen Lim

We investigate the security of continuous-variable (CV) quantum key distribution (QKD) using coherent states in the presence of quadrature excess noise. We consider an eavesdropping attack which uses a linear amplifier and beam splitter.…

Quantum Physics · Physics 2009-11-11 Ryo Namiki , Takuya Hirano

We introduce a robust scheme for long-distance continuous-variable (CV) measurement-device-independent (MDI) quantum key distribution (QKD) in which we employ post-selection between distant parties communicating through the medium of an…

Multi-carrier continuous-variable quantum key distribution (CV-QKD) is considered to be a promising way to boost the secret key rate (SKR) over the existing single-carrier CV-QKD scheme. However, the extra excess noise induced in the…

Quantum Physics · Physics 2023-03-22 Heng Wang , Yan Pan , Yun Shao , Yaodi Pi , Ting Ye , Yang Li , Tao Zhang , Jinlu Liu , Jie Yang , Li Ma , Wei Huang , Bingjie Xu

Nonlocal quantum gates, coupling quantum systems located at distance, are crucial for distributed quantum computing. High-capacity optical noiseless connections between these quantum systems are essential for transmitting large amounts of…

Quantum Physics · Physics 2026-03-16 Michele N. Notarnicola , Radim Filip

Information reconciliation is crucial for continuous-variable quantum key distribution (CV-QKD) because its performance affects the secret key rate and maximal secure transmission distance. Fixed-rate error correction codes limit the…

Quantum Physics · Physics 2019-11-11 Chao Zhou , Xiangyu Wang , Yi-Chen Zhang , Zhiguo Zhang , Song Yu , Hong Guo

We experimentally demonstrate a long-distance quantum communication at 143 km between the city of Kazan and the urban-type village of Apastovo in the Republic of Tatarstan by using quantum key distribution prototype providing high…

Quantum key distribution (QKD) offers a theoretically secure method to share secret keys, yet practical implementations face challenges due to noise and loss over long-distance channels. Traditional QKD protocols require extensive noise…

Quantum Physics · Physics 2025-08-01 Hannah Seabrook , Emilien Lavie , Teodor Strömberg , Matthew P. Stafford , Giulia Rubino

In this paper, we derive a closed form expression for the output state of a CV-QKD protocol in the presence of zero-photon catalysis (ZPC) and quantum scissor (QS). Then, based on this closed form solution, we use direct search algorithm to…

Quantum Physics · Physics 2023-12-19 Khatereh Jafari , Mojtaba Golshani , Alireza Bahrampour

The discrete modulation can make up for the shortage of transmission distance in measurement-device-independent continuous-variable quantum key distribution (MDI-CVQKD) that has an unique advantage against all side-channel attacks but also…

Quantum Physics · Physics 2020-04-23 Wei Ye , Ying Guo , Yun Mao , Hai Zhong , Liyun Hu

We propose a novel continuous-variable quantum key distribution (CVQKD) protocol that employs orthogonal frequency-division multiplexing (OFDM) in the terahertz (THz) band to enable high-throughput and secure quantum communication. By…

Quantum Physics · Physics 2025-07-01 Mingqi Zhang , Kaveh Delfanazari

In this paper, using the full security framework for continuous variable quantum key distribution (CV-QKD), we provide a composable security proof for the CV-QKD system in a realistic implementation. We take into account equipment losses…

Quantum Physics · Physics 2022-09-19 Roman Goncharov , Alexei D. Kiselev , Eduard Samsonov , Vladimir Egorov

To achieve the maximum information transfer and face a possible eavesdropper, the samples transmitted in continuous-variable quantum key distribution (CV-QKD) protocols are to be drawn from a continuous Gaussian distribution. As a matter of…

We propose a quantum repeater for continuous variable (CV) quantum optical states. Our repeater relies on an error correction protocol for loss on CV states based on CV teleportation and entanglement distillation via noiseless linear…

Quantum Physics · Physics 2015-05-15 Josephine Dias , Tim Ralph

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

Here, we demonstrate that a practical Continuous Variables Quantum Key Distribution (CVQKD) protocol relying on the Gaussian modulation of coherent states features secret key rates that cannot be achieved with standard qubit Discrete…

Quantum Physics · Physics 2014-10-24 Paul Jouguet , David Elkouss , Sébastien Kunz-Jacques

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
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