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One of the challenges in practical quantum key distribution is dealing with efficiency mismatch between different threshold single-photon detectors. There are known bounds for the secret key rate for the BB84 protocol with…

Quantum Physics · Physics 2019-03-06 M. K. Bochkov , A. S. Trushechkin

We present and analyze a quantum key distribution protocol based on sending entangled N-qubit states instead of single-qubit ones as in the trail-blazing scheme by Bennett and Brassard (BB84). Since the qubits are sent individually, an…

Quantum Physics · Physics 2008-10-07 Olli Ahonen , Mikko Mottonen , Jeremy L. O'Brien

The decoy-state Bennett-Brassard 1984 (BB84) quantum key distribution (QKD) protocol is widely regarded as the de facto standard for practical implementations. On the receiver side, passive basis choice is attractive because it…

Quantum Physics · Physics 2025-11-27 Akihiro Mizutani , Shun Kawakami , Go Kato

The Bennett-Brassard 1984 protocol (BB84 protocol) is one of the simplest protocols for implementing quantum key distribution (QKD). In the protocol, the sender and the receiver iteratively choose one of two complementary measurement bases.…

Quantum Physics · Physics 2025-12-01 Shun Kawakami , Atsushi Taniguchi , Yoshihide Tonomura , Koichi Takasugi , Koji Azuma

I prove the security of quantum key distribution against individual attacks for realistic signals sources, including weak coherent pulses and downconversion sources. The proof applies to the BB84 protocol with the standard detection scheme…

Quantum Physics · Physics 2009-10-31 Norbert Lütkenhaus

Security proofs of quantum key distribution (QKD) typically assume that the devices of the legitimate users are perfectly shielded from the eavesdropper. This assumption is, however, very hard to meet in practice, and thus the security of…

Quantum Physics · Physics 2018-09-05 Weilong Wang , Kiyoshi Tamaki , Marcos Curty

The Bennett-Brassard 1984 (BB84) protocol is the most widely implemented quantum key distribution (QKD) scheme. However, despite enormous theoretical and experimental efforts in the past decades, the security of this protocol with imperfect…

We prove the security of the Bennett-Brassard (BB84) quantum key distribution protocol in the case where the key information is encoded in the relative phase of a coherent-state reference pulse and a weak coherent-state signal pulse, as in…

Quantum Physics · Physics 2008-02-27 Hoi-Kwong Lo , John Preskill

The security of quantum key distribution (QKD) has been proven for different protocols, in particular for the BB84 protocol. It has been shown that this scheme is robust against eventual imperfections in the state preparation, and sending…

Quantum Physics · Physics 2018-12-05 Davide Rusca , Alberto Boaron , Marcos Curty , Anthony Martin , Hugo Zbinden

We analyse the finite-size security of the efficient Bennett-Brassard 1984 protocol implemented with decoy states and apply the results to a gigahertz-clocked quantum key distribution system. Despite the enhanced security level, the…

Quantum Cryptography or Quantum key distribution (QKD) is a technique that allows the secure distribution of a bit string, used as key in cryptographic protocols. When it was noted that quantum computers could break public key cryptosystems…

Cryptography and Security · Computer Science 2010-07-15 Mohamed Elboukhari , Mostafa Azizi , Abdelmalek Azizi

Quantum key distribution (QKD) protocols with threshold detectors are driving high-performance QKD demonstrations. The corresponding security proofs usually assume that all physical detectors have the same detection efficiency. However, the…

Quantum Physics · Physics 2021-02-02 Yanbao Zhang , Patrick J. Coles , Adam Winick , Jie Lin , Norbert Lutkenhaus

We review the current status of security proofs for practical decoy-state Quantum Key Distribution using the BB84 protocol, focusing on optical implementations with weak coherent pulses and threshold photodetectors. The primary aim of this…

Quantum Physics · Physics 2025-05-19 Devashish Tupkary , Ernest Y. -Z. Tan , Shlok Nahar , Lars Kamin , Norbert Lütkenhaus

The lists of bits processed in quantum key distribution are necessarily of finite length. The need for finite-key unconditional security bounds has been recognized long ago, but the theoretical tools have become available only very…

Quantum Physics · Physics 2015-05-13 Raymond Y. Q. Cai , Valerio Scarani

We devise a simple modification that essentially doubles the efficiency of a well-known quantum key distribution scheme proposed by Bennett and Brassard (BB84). Our scheme assigns significantly different probabilities for the different…

Quantum Physics · Physics 2007-05-23 M. Ardehali , H. F. Chau , Hoi-Kwong Lo

Device imperfections and memory effects can result in undesired correlations among the states generated by a realistic quantum source. These correlations are called source correlations. Proving the security of quantum key distribution (QKD)…

Quantum Physics · Physics 2025-08-05 Ashutosh Marwah , Frédéric Dupuis

We introduce a quantum cloning bound which we apply to a straightforward and relatively direct security proof of the prepare-and-measure Bennett-Brassard 1984 (BB84) quantum key distribution (QKD) protocol against collective attacks. The…

Quantum Physics · Physics 2013-08-15 Erik Woodhead

Quantum Key Distribution with the BB84 protocol has been shown to be unconditionally secure even using weak coherent pulses instead of single-photon signals. The distances that can be covered by these methods are limited due to the loss in…

Quantum Physics · Physics 2009-11-10 Marcos Curty , Norbert Lütkenhaus

This paper proposes a new protocol for quantum dense key distribution. This protocol embeds the benefits of a quantum dense coding and a quantum key distribution and is able to generate shared secret keys four times more efficiently than…

We present a new technique for proving the security of quantum key distribution (QKD) protocols. It is based on direct information-theoretic arguments and thus also applies if no equivalent entanglement purification scheme can be found.…

Quantum Physics · Physics 2009-11-11 R. Renner , N. Gisin , B. Kraus