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We demonstrate that secure quantum key distribution systems based on continuous variables implementations can operate beyond the apparent 3 dB loss limit that is implied by the beam splitting attack . The loss limit was established for…

Quantum Physics · Physics 2009-11-07 Ch. Silberhorn , T. C. Ralph , N. Lütkenhaus , G. Leuchs

Quantum communications promise to revolutionise the way information is exchanged and protected. Unlike their classical counterpart, they are based on dim optical pulses that cannot be amplified by conventional optical repeaters.…

Quantum Physics · Physics 2019-10-07 M. Minder , M. Pittaluga , G. L. Roberts , M. Lucamarini , J. F. Dynes , Z. L. Yuan , A. J. Shields

A novel integrated optical source capable of emitting faint pulses with different polarization states and with different intensity levels at 100 MHz has been developed. The source relies on a single laser diode followed by four…

We present a composable security proof, valid against arbitrary attacks and including finite-size effects, for a high dimensional time-frequency quantum key distribution (TFQKD) protocol based upon spectrally entangled photons. Previous…

Quantum Physics · Physics 2016-09-30 Nathan Walk , Jonathan Barrett , Joshua Nunn

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

Quantum key distribution (QKD) offers an unconditionally secure means of communication based on the laws of quantum mechanics. Currently, a major challenge is to achieve a QKD system with a 40 dB channel loss, which is required if we are to…

Quantum key distribution (QKD) allows two distant parties to share secret keys with the proven security even in the presence of an eavesdropper with unbounded computational power. Recently, GHz-clock decoy QKD systems have been realized by…

We report an optical link of 540 km for ultrastable frequency distribution over the Internet fiber network. The stable frequency optical signal is processed enabling uninterrupted propagation on both directions. The robustness and the…

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…

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

Constrained devices, such as smart sensors, wearable devices, and Internet of Things nodes, are increasingly prevalent in society and rely on secure communications to function properly. These devices often operate autonomously, exchanging…

Most continuous-variable quantum key distribution schemes are based on the Gaussian modulation of coherent states followed by continuous quadrature detection using homodyne detectors. In all previous schemes, the Gaussian modulation has…

Quantum Physics · Physics 2016-09-06 Tobias Gehring , Christian S. Jacobsen , Ulrik L. Andersen

Quantum key distribution (QKD) provides information-theoretic security guaranteed by the laws of quantum mechanics, making it resistant to future computational threats, including quantum computers. While QKD technology shows great promise,…

Quantum Physics · Physics 2025-04-14 Si Qi Ng , Florian Kanitschar , Gong Zhang , Chao Wang

We propose the improved decoy state quantum key distribution incorporating finite statistics due to the finite code length and report on its demonstration. In our experiment, four different intensities including the vacuum state for optimal…

Quantum Physics · Physics 2007-05-23 Jun Hasegawa , Masahito Hayashi , Tohya Hiroshima , Akihiro Tanaka , Akihisa Tomita

The noise in optical source needs to be characterized for the security of continuous-variable quantum key distribution (CVQKD). Two feasible schemes, based on either active optical switch or passive beamsplitter are proposed to monitor the…

Quantum Physics · Physics 2015-06-03 Jian Yang , Xiang Peng , Hong Guo

Mitigating noise-induced decoherence is the central challenge in controlling open quantum systems. While existing robust protocols often require precise noise models, we introduce a universal framework for noise-agnostic quantum control…

Quantum Physics · Physics 2026-03-18 Lixiang Ding , Jingtao Fan , Xingze Qiu

Noiseless linear amplifiers (NLAs) serve as an effective means to enable long-distance continuous-variable (CV) quantum key distribution (QKD), even under realistic conditions with non-unit reconciliation efficiency. Separately, unitary…

Establishing secure data communication necessitates secure key exchange over a public channel. Quantum key distribution (QKD), which leverages the principles of quantum physics, can achieve this with information-theoretic security. The…

The coherent one-way (COW) quantum key distribution (QKD) is a highly practical quantum communication protocol that is currently deployed in off-the-shelves products. However, despite its simplicity and widespread use, the security of…

Quantum Physics · Physics 2022-12-26 Emilien Lavie , Charles C. -W. Lim

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…

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