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The simplest device-independent quantum key distribution protocol is based on the Clauser-Horne-Shimony-Holt (CHSH) Bell inequality and allows two users, Alice and Bob, to generate a secret key if they observe sufficiently strong…

Quantum Physics · Physics 2021-04-27 Erik Woodhead , Antonio Acín , Stefano Pironio

IBM Quantum offers free remote access to real quantum processors. One of the many experiments now accessible to all students is a test of Bell inequalities. This experiment introduces the rigorous mysteries that physicists have grappled…

Physics Education · Physics 2023-03-08 Jed Brody , Robert Avram

We have implemented an experimental set-up in order to demonstrate the feasibility of time-coding protocols for quantum key distribution. Alice produces coherent 20 ns faint pulses of light at 853 nm. They are sent to Bob with delay 0 ns…

Quantum Physics · Physics 2007-05-23 William Boucher , Thierry Debuisschert

Quantum Cryptography, or more accurately, Quantum Key Distribution (QKD) is based on using an unconditionally secure ``quantum channel'' to share a secret key among two users. A manufacturer of QKD devices could, intentionally or not, use a…

Quantum Physics · Physics 2022-03-16 Jan-Åke Larsson

We investigate a new strategy for incoherent eavesdropping in Ekert's entanglement based quantum key distribution protocol. We show that under certain assumptions of symmetry the effectiveness of this strategy reduces to that of the…

Quantum Physics · Physics 2009-11-07 Hitoshi Inamori , Luke Rallan , Vlatko Vedral

We discuss Bell nonlocality in quantum networks with unreliable sources. Our main result is a condition on the observed data which ensures that inconclusive events can be safely discarded, without introducing any loophole. More formally, we…

Quantum Physics · Physics 2025-12-11 Sadra Boreiri , Nicolas Brunner , Pavel Sekatski

Security of an ideal system for quantum key distribution can be formally proved. However, technological imperfections of real systems can be misused by an eavesdropper to get information about the key without causing a detectable change in…

Quantum Physics · Physics 2016-04-21 Miloslav Dušek , Siddarth Koduru Joshi

In this Paper, we investigate the security of Zhang, Li and Guo quantum key distribution via quantum encryption protocol [$\text{Phys. Rev. A} \textbf{64}, 24302 (2001)$] and show that it is not secure against some of Eve's attacks and with…

Quantum Physics · Physics 2007-05-23 A. Fahmi

Quantum cryptography shows that one can guarantee the secrecy of correlation on the sole basis of the laws of physics, that is without limiting the computational power of the eavesdropper. The usual security proofs suppose that the…

Quantum Physics · Physics 2009-11-13 Valerio Scarani , Nicolas Gisin , Nicolas Brunner , Lluis Masanes , Sergi Pino , Antonio Acin

Secure key distribution among two remote parties is impossible when both are classical, unless some unproven (and arguably unrealistic) computation-complexity assumptions are made, such as the difficulty of factorizing large numbers. On the…

Quantum Physics · Physics 2011-11-01 Michel Boyer , Ran Gelles , Dan Kenigsberg , Tal Mor

We propose a new quantum key distribution scheme that is based on the optimum expectation values of maximally entangled Greenberger-Horne-Zeilinger states. Our protocol makes use of the degrees of freedom in continuously variable angles,…

Quantum Physics · Physics 2023-08-21 Hyung S. Choi , Ye Jin Han , Collin Kessinger , Qiaoren Wang

A new protocol for quantum key distribution based on entanglement swapping is presented. In this protocol, both certain key and random key can be generated without any loss of security. It is this property differs our protocol from the…

Quantum Physics · Physics 2007-05-23 Chong Li , He-Shan Song , Ling Zhou , Chun-Feng Wu

This paper discusses the use of computer-aided verification as a practical means for analysing quantum information systems; specifically, the BB84 protocol for quantum key distribution is examined using this method. This protocol has been…

Cryptography and Security · Computer Science 2007-05-23 Rajagopal Nagarajan , Nikolaos Papanikolaou , Garry Bowen , Simon Gay

We introduce a quantum key distribution protocol designed to expose fake users that connect to Alice or Bob for the purpose of monopolising the link and denying service. It inherently resists attempts to exhaust Alice and Bob's initial…

Quantum Physics · Physics 2017-11-15 Alasdair B. Price , John G. Rarity , Chris Erven

The violation of a Bell inequality is an experimental observation that forces one to abandon a local realistic worldview, namely, one in which physical properties are (probabilistically) defined prior to and independent of measurement and…

In this paper we investigate properties of several randomness generation protocols in the device independent framework. Using Bell-type inequalities it is possible to certify that the numbers generated by an untrusted device are indeed…

Quantum Physics · Physics 2013-09-25 Piotr Mironowicz , Marcin Pawłowski

Recently, in Sci. Rep. \textbf{6} (2016) 28767, Li et al., have proposed a scheme for quantum key distribution using Bell states. This comment provides a proof that the proposed scheme of Li et al., is insecure as it involves leakage of…

Quantum Physics · Physics 2016-09-26 Anirban Pathak , Kishore Thapliyal

Semi-quantum private comparison (SQPC) enables two classical users with limited quantum capabilities to compare confidential information using a semi-honest third party (TP) with full quantum power. However, entanglement swapping, as an…

Quantum Physics · Physics 2023-08-28 Chong-Qiang Ye , Jian Li , Xiu-Bo Chen , Yanyan Hou

We propose a quantum key distribution (QKD) protocol that is carried out in an indefinite causal order (ICO). In QKD, one considers a setup in which two parties, Alice and Bob, share a key with one another in such a way that they can detect…

Quantum Physics · Physics 2025-12-08 Hector Spencer-Wood

We report on an experimental demonstration of the modified Ekert 91 protocol of quantum key distribution using a hybrid entanglement source with two different degrees of freedoms, a 1550 nm time-bin qubit and 810 nm polarization qubit. The…