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We show how weak non-linearities can be used in a device-independent quantum key distribution (QKD) protocol using generalized two-mode Schr\"odinger cat states. The QKD protocol is therefore shown to be secure against collective attacks…

Quantum Physics · Physics 2015-08-12 Curtis J. Broadbent , Kevin Marshall , Christian Weedbrook , John C. Howell

Bell nonlocality between distant quantum systems---i.e., joint correlations which violate a Bell inequality---can be verified without trusting the measurement devices used, nor those performing the measurements. This leads to…

Quantum Physics · Physics 2015-01-16 Sacha Kocsis , Michael J. W. Hall , Adam J. Bennet , Dylan J. Saunders , G. J. Pryde

Measurement-device-independent quantum key distribution (MDI-QKD) can eliminate all detector side-channel loopholes and has shown excellent performance in long-distance secret keys sharing. Conventional security proofs, however, require…

Quantum Physics · Physics 2022-02-09 Hua-Jian Ding , Xing-Yu Zhou , Chun-Hui Zhang , Jian Li , Qin Wang

We consider the characterization of entanglement depth in a quantum many-body system from the device-independent perspective; i.e., certifying how many particles are genuinely entangled without relying on assumptions on the system itself…

Device-independent quantum key distribution (DIQKD) aims to mitigate adversarial exploitation of imperfections in quantum devices, by providing an approach for secret key distillation with modest security assumptions. Advantage…

Quantum Physics · Physics 2025-03-11 Mikka Stasiuk , Norbert Lütkenhaus , Ernest Y. -Z. Tan

The intensity correlations due to imperfect modulation during the quantum-state preparation in a measurement-device-independent quantum key distribution (MDI QKD) system compromise its security performance. Therefore, it is crucial to…

Quantum Physics · Physics 2024-10-08 Junxuan Liu , Tianyi Xing , Ruiyin Liu , Zihao Chen , Hao Tan , Anqi Huang

A practical quantum key distribution (QKD) protocol necessarily runs in finite time and, hence, only a finite amount of communication is exchanged. This is in contrast to most of the standard results on the security of QKD, which only hold…

Quantum Physics · Physics 2009-01-08 Valerio Scarani , Renato Renner

Violation of Bell's inequality has been the mainspring for secure key generation in an entanglement assisted Quantum Key Distribution(QKD) protocol. Various contributions have relied on the violation of appropriate Bell inequalities to…

Quantum Physics · Physics 2023-04-19 Kaushiki Mukherjee , Tapaswini Patro , Nirman Ganguly

Random generation and confidential distribution of cryptographic keys are fundamental building blocks of secure communication. Using quantum states in which the transmitted quantum bit is entangled with a stationary memory quantum bit…

Quantum Physics · Physics 2021-11-30 Pascal Kobel , Ralf A. Berner , Michael Köhl

Quantum key distribution (QKD) protocols aim at allowing two parties to generate a secret shared key. While many QKD protocols have been proven unconditionally secure in theory, practical security analyses of experimental QKD…

Quantum Physics · Physics 2023-07-04 Michel Boyer , Gilles Brassard , Nicolas Godbout , Rotem Liss , Stéphane Virally

Quantum key distribution (QKD) achieves information-theoretic security, without relying on computational assumptions, by distributing quantum states. To establish secret bits, two honest parties exploit key distillation protocols over…

Quantum Physics · Physics 2026-02-06 Rutvij Bhavsar , Junguk Moon , Joonwoo Bae

This paper introduces a novel device-independent quantum self-testing protocol designed specifically for multipartite quantum communication. By exploiting the quantum rigidity in Bell nonlocality, the protocol enables the certification of…

Quantum Physics · Physics 2025-04-14 Chon-Fai Kam , En-Jui Kuo

Bell inequalities have traditionally been used to demonstrate that quantum theory is nonlocal, in the sense that there exist correlations generated from composite quantum states that cannot be explained by means of local hidden variables.…

Device-independent quantum key distribution aims at providing security guarantees even when using largely uncharacterised devices. In the simplest scenario, these guarantees are derived from the CHSH score, which is a simple linear…

Quantum Physics · Physics 2021-04-28 P. Sekatski , J. -D. Bancal , X. Valcarce , E. Y. -Z. Tan , R. Renner , N. Sangouard

According to quantum theory, the outcomes obtained by measuring an entangled state necessarily exhibit some randomness if they violate a Bell inequality. In particular, a maximal violation of the CHSH inequality guarantees that 1.23 bits of…

Quantum Physics · Physics 2012-03-23 Antonio Acin , Serge Massar , Stefano Pironio

Mediated semi-quantum key distribution (M-SQKD) permits two limited "semi-quantum" or "classical" users to establish a secret key with the help of a third party (TP), in which TP has fully quantum power and may be untrusted. Several…

Quantum Physics · Physics 2022-09-07 Chong-Qiang Ye , Jian Li , Xiu-Bo Chen , Yan-Yan Hou

The quantum key distribution (QKD), guaranteed by the principle of quantum physics, is a promising solution for future secure information and communication technology. However, device imperfections compromise the security of real-life QKD…

Quantum Physics · Physics 2022-09-14 Ye Chen , Chunfeng Huang , Zihao Chen , Wenjie He , Chengxian Zhang , Shihai Sun , Kejin Wei

The device-independent approach to quantum key distribution (QKD) aims to establish a secret key between two or more parties with untrusted devices, potentially under full control of a quantum adversary. The performance of a QKD protocol…

Quantum Physics · Physics 2018-02-07 Timo Holz , Hermann Kampermann , Dagmar Bruß

Although quantum key distribution (QKD) is theoretically secure, there is a gap between the theory and practice. In fact, real-life QKD may not be secure because component devices in QKD systems may deviate from the theoretical models…

Quantum key distribution (QKD) is the most explored application of quantum information theory. A central problem in entanglement-based QKD (EB-QKD), is whether every entangled state can be used to extract a key. We observe that entanglement…

Quantum Physics · Physics 2026-03-09 Shubhayan Sarkar , Tushita Prasad , Karol Horodecki