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A global continuous-variable quantum key distribution (CV-QKD) network can be established using a series of satellite-to-Earth channels. Increased performance in such a network is provided by performing coherent measurement of the optical…

Quantum Physics · Physics 2025-08-13 Nathan K Long , Robert Malaney , Kenneth J Grant

Compared to fiber continuous-variable quantum key distribution (CVQKD), atmospheric link offers the possibility of a broader geographical coverage and more flexible transmission.However, there are many negative features of the atmospheric…

Quantum Physics · Physics 2018-10-23 Shiyu Wang , Peng Huang , Tao Wang , Guihua Zeng

Quantum correlations between imprecision and back-action are a hallmark of continuous linear measurements. Here we study how measurement-based feedback can be used to improve the visibility of quantum correlations due to the interaction of…

The field of space communications is the realm of communication technologies where diffraction and atmospheric effects, both of which contribute to loss and noise, become overriding. The pertinent questions here are how and at which rate…

Quantum Physics · Physics 2023-10-27 Masoud Ghalaii , Stefano Pirandola

We address a continuous-variable quantum key distribution (CV-QKD) protocol employing quaternary phase-shift-keying (QPSK) of coherent states and a non-Gaussian measurement inspired by quantum receivers minimizing the error probability in a…

Quantum Physics · Physics 2023-10-13 Michele N. Notarnicola , Marcin Jarzyna , Stefano Olivares , Konrad Banaszek

We propose a method to track signals from quadrant photodiodes (QPD) in heterodyne laser interferometers that employ digital phase-locked loops for phase readout. Instead of separately tracking the four segments from the QPD and then…

Instrumentation and Detectors · Physics 2020-11-17 Gerhard Heinzel , Miguel Dovale Álvarez , Alvise Pizzella , Nils Brause , Juan José Esteban Delgado

Quantum key distribution (QKD offers a long-term solution to establish information-theoretically secure keys between two distant users. In practice, with a careful characterization of quantum sources and the decoy-state method,…

We propose and demonstrate a fully passive discrete-state continuous-variable quantum key distribution (CV-QKD), which can eliminate all modulator side channels on the source side, using a local local oscillator (LLO). The CV-QKD system…

Quantum Physics · Physics 2026-05-04 Yu Zhang , Xuyang Wang , Chenyang Li , Jie Yun , Qiang Zeng , Zhiliang Yuan , Zhenguo Lu , Yongmin Li

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

In this paper we report a continuous-variable quantum key distribution protocol using multimode coherent states generated on subcarrier frequencies of the optical spectrum. To detect the quadrature components of bosonic field we propose a…

In this paper, we study the feasibility of conducting quantum key distribution (QKD) together with classical communication through the same optical fiber by employing dense-wavelength-division-multiplexing (DWDM) technology at telecom…

Quantum Physics · Physics 2015-05-19 Bing Qi , Wen Zhu , Li Qian , Hoi-Kwong Lo

The phase randomized light is one of the key assumptions in the security proof of Bennett-Brassard 1984 (BB84) quantum key distribution (QKD) protocol implemented with an attenuated laser. Though the assumption has been believed to be…

Quantum Physics · Physics 2015-06-22 Toshiya Kobayashi , Akihisa Tomita , Atsushi Okamoto

We propose a long-distance continuous-variable quantum key distribution (CVQKD) with four-state protocol using non-Gaussian state-discrimination detection. A photon subtraction operation, which is deployed at the transmitter, is used for…

Quantum Physics · Physics 2018-07-23 Qin Liao , Ying Guo , Duang Huang , Peng Huang , Guihua Zeng

The cross-correlation sensitivity of two identical balanced photodiode heterodyne receivers is characterized. Both balanced photodiodes receive the same weak signal split up equally, a situation equivalent to an astronomical spatial…

Quantum Physics · Physics 2021-01-15 E. A. Michael , F. E. Besser

This paper proposes a multi-mode Gaussian modulated continuous variable quantum key distribution (CV-QKD) scheme able to operate at high bandwidth despite using conventional noisy, coherent detectors. We demonstrate enhancement in shotnoise…

Quantum Physics · Physics 2019-07-24 Rupesh Kumar , Xinke Tang , Adrian Wonfor , Richard Penty , Ian White

Continuous variable quantum key distribution (CV-QKD), utilizes continuous variables encoding such as the quadra-ture components of the quantized electromagnetic field and coherent detection decoding, offering good compatibility with the…

Quantum Physics · Physics 2025-07-22 Pu Wang , Yan Tian , Yongmin Li

The security of quantum key distribution (QKD) is severely threatened by discrepancies between realistic devices and theoretical assumptions. Recently, a significant framework called the reference technique was proposed to provide security…

Quantum Physics · Physics 2022-11-21 Jie Gu , Xiao-Yu Cao , Yao Fu , Zong-Wu He , Ze-Jie Yin , Hua-Lei Yin , Zeng-Bing Chen

Transmission losses through optical fibers are one of the main obstacles preventing both long-distance quantum communications and continuous-variable quantum key distribution. Optical amplification provides a tool to obtain, at least…

Quantum Physics · Physics 2025-01-27 Michele N. Notarnicola , Filip Cieciuch , Marcin Jarzyna

A continuous variable (CV), measurement device independent (MDI) quantum key distribution (QKD) protocol is analyzed, enabling three parties to connect for quantum conferencing. We utilise a generalised Bell detection at an untrusted relay…

Quantum Physics · Physics 2022-10-19 Alasdair I. Fletcher , Stefano Pirandola

Variable measurement operators enable the optimization of strategies for testing quantum properties and the preparation of a range of quantum states. Here, we experimentally implement a weak-field homodyne detector that can continuously…