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We report a large area photo-diode based homodyne detector for free-space quantum coherent communication. The detector's performance is studied in terms of detection bandwidth and electronic noise for shot-noise limited quantum signal…

Quantum Physics · Physics 2020-11-10 Rupesh Kumar , Igor Konieczniak , Gerald Bonner , Tim Spiller

We present a quantum receiver for quadrature amplitude modulation (QAM) coherent states discrimination with homodyne-displacement hybrid structure. Our strategy is to carry out two successive measurements on parts of the quantum states. The…

Quantum Physics · Physics 2015-04-21 Tian Chen , Ke Li , Yuan Zuo , Bing Zhu

Quantum Key Distribution (QKD) in principle offers unconditional security based on the laws of physics. Continuous variable (CV) quantum key distribution has the potential for high-key-rate and low-cost implementations using standard…

Quantum Physics · Physics 2021-10-19 Chenyang Li , Li Qian , Hoi-Kwong Lo

We use the Gaussian approximation describing photocount statistics for both the homodyne and the double homodyne (heterodyne) measurements to study asymmetry effects arising from imbalance of the beam splitters and variations in quantum…

Quantum Physics · Physics 2025-12-30 A. S. Naumchik , Roman K. Goncharov , Alexei D. Kiselev

In this letter, we propose a quantum integrated sensing and communication scheme for a quantum optical link using binary phase-shift keying modulation and homodyne detection. The link operates over a phase-insensitive Gaussian channel with…

Information Theory · Computer Science 2026-01-13 Ioannis Krikidis

We present a rigorous security analysis of Continuous-Variable Measurement-Device Independent Quantum Key Distribution (CV MDI QKD) in a finite size scenario. The security proof is obtained in two steps: by first assessing the security…

Quantum Physics · Physics 2018-06-12 Cosmo Lupo , Carlo Ottaviani , Panagiotis Papanastasiou , Stefano Pirandola

Quantum Key Distribution (QKD) can provide information-theoretically secure communications and is a strong candidate for the next generation of cryptography. However, in practice, the performance of QKD is limited by "practical…

Quantum Physics · Physics 2020-04-24 Wenyuan Wang

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

Continuous-variable quantum key distribution (CV-QKD) enables information-theoretically secure key generation between legitimate parties. To further enhance system performance, an improved two-way CV-QKD protocol has been proposed, which is…

Quantum Physics · Physics 2026-01-28 Yanhao Sun , Jiayu Ma , Xiangyu Wang , Song Yu , Ziyang Chen , Hong Guo

Future interferometric gravitational wave detectors will make use of the coupling between shot noise and radiation pressure noise that produces a squeezed output for the quantum noise at the dark-port of the interferometer allowing these…

General Relativity and Quantum Cosmology · Physics 2007-05-23 Peter T. Beyersdorf

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

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…

We present an analysis of the time domain measurement of temporally resolvable quantum states using balanced homodyne detection. Our approach outlines a formalism of detecting quantum states in arbitrary temporal modes via projection of the…

Quantum Physics · Physics 2026-02-17 Owen Sandner , Brendan Mackey , Yuyang Liu , Connor Kupchak , Andrew MacRae

We present a finite-size security proof of the decoy-state BB84 QKD protocol against coherent attacks, using entropic uncertainty relations, for imperfect detectors. We apply this result to the case of detectors with imperfectly…

Quantum Physics · Physics 2025-12-16 Devashish Tupkary , Shlok Nahar , Pulkit Sinha , Norbert Lütkenhaus

We study the sensitivity of phase estimation in a lossy Mach-Zehnder interferometer (MZI) using two general, and practical, resources generated by a laser and a nonlinear optical medium with passive optimal elements, which are readily…

Quantum Physics · Physics 2017-12-07 Changhun Oh , Su-Yong Lee , Hyunchul Nha , Hyunseok Jeong

Achieving higher sensitivity is an earnest purpose for precision metrology. As a response to this goal, the weak value amplification approach has been developed for measuring ultra-small physical effects, realizing sensitivity that had…

Quantum Physics · Physics 2019-07-24 Jingzheng Huang , Yanjia Li , Chen Fang , Hongjing Li , Guihua Zeng

Photon addition operations applied to squeezed states have been shown to significantly enhance phase sensitivity. In this study, we extend this approach by applying photon addition not only to coherent states but also within a Mach--Zehnder…

Quantum Physics · Physics 2025-10-21 Qisi Zhou , Qingqian Kang , Teng Zhao , Xin Su , Cunjin Liu , Liyun Hu

Quantum continuous variables are being explored as an alternative means to implement quantum key distribution, which is usually based on single photon counting. The former approach is potentially advantageous because it should enable higher…

Quantum Physics · Physics 2009-11-10 F. Grosshans , G. Van Assche , J. Wenger , R. Brouri , N. J. Cerf , Ph. Grangier

We assess the security of a quantum key distribution protocol relying on the transmission of Gaussian-modulated coherent states and homodyne detection. This protocol is shown to be equivalent to a squeezed state protocol based on a CSS code…

Quantum Physics · Physics 2009-11-10 S. Iblisdir , G. Van Assche , N. J. Cerf

Measurement-device-independent quantum key distribution protocol, whose security analysis does not rely on any assumption on the detection system, can immune the attacking against detectors. We give a first composable security analysis for…

Quantum Physics · Physics 2018-09-05 Ziyang Chen , Yi-Chen Zhang , Gan Wang , Zhengyu Li , Hong Guo