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Quantum key distribution is a way to distribute secret keys to distant users with information theoretic security and key rates suitable for real-world applications. Its rate-distance figure, however, is limited by the natural loss of the…

Quantum Physics · Physics 2018-09-12 Kiyoshi Tamaki , Hoi-Kwong Lo , Wenyuan Wang , Marco Lucamarini

Quantum key distribution promises unconditionally secure communications. However, as practical devices tend to deviate from their specifications, the security of some practical systems is no longer valid. In particular, an adversary can…

Quantum Physics · Physics 2015-06-16 Marcos Curty , Feihu Xu , Wei Cui , Charles Ci Wen Lim , Kiyoshi Tamaki , Hoi-Kwong Lo

We prove that the results of a finite set of general quantum measurements on an arbitrary dimensional quantum system can be simulated using a polynomial (in measurements) number of hidden-variable states. In the limit of infinitely many…

Quantum Physics · Physics 2008-11-11 Borivoje Dakic , Milovan Suvakov , Tomasz Paterek , Caslav Brukner

Coherent state photon sources are widely used in quantum information processing. In many applications, such as quantum key distribution (QKD), a coherent state is functioned as a mixture of Fock states by assuming its phase is continuously…

Quantum Physics · Physics 2015-05-15 Zhu Cao , Zhen Zhang , Hoi-Kwong Lo , Xiongfeng Ma

A method to hide certain quantum states in a superposition will be proposed. Such method can be used to increase the security of a communication channel. States represent an encrypted message will disappear during data exchange. This makes…

Quantum Physics · Physics 2008-07-31 Ahmed Younes

Schmidt decomposition is a widely employed tool of quantum theory which plays a key role for distinguishable particles in scenarios such as entanglement characterization, theory of measurement and state purification. Yet, it is held not to…

Quantum Physics · Physics 2017-03-29 Stefania Sciara , Rosario Lo Franco , Giuseppe Compagno

This letter examines the consequences of a recently proposed modification of the postulate of equal {\it a priori} probability in quantum statistical mechanics. This modification, called the {\it quantum microcanonical postulate} (QMP),…

Quantum Physics · Physics 2007-05-23 Carl M Bender , Dorje C Brody , Daniel W Hook

A classic and fundamental result about the decomposition of random sequences into a mixture of simpler ones is de Finetti's Theorem. In its original form it applies to infinite 0-1 valued exchangeable sequences. Later it was extended and…

Probability · Mathematics 2021-11-16 Andras Farago

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

As quantum technologies advance, the ability to generate increasingly large quantum states has experienced rapid development. In this context, the verification and estimation of large entangled systems represents one of the main challenges…

Quantum Physics · Physics 2022-03-30 Joshua Morris , Valeria Saggio , Aleksandra Gočanin , Borivoje Dakić

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

We provide a new quantum algorithm that efficiently determines the quality of a least-squares fit over an exponentially large data set by building upon an algorithm for solving systems of linear equations efficiently (Harrow et al., Phys.…

Quantum Physics · Physics 2013-01-10 Nathan Wiebe , Daniel Braun , Seth Lloyd

Quantum Key Distribution (QKD) stands as a revolutionary approach to secure communication, using the principles of quantum mechanics to establish unbreakable channels. Unlike traditional cryptography, which relies on the computational…

Quantum Physics · Physics 2025-09-09 Alec L. Riso , Karthik Thyagarajan , Connor Whiting , Katherine Jimenez

It has been shown recently that the framework of quantum sampling, as introduced by Bouman and Fehr, can lead to new entropic uncertainty relations highly applicable to finite-key cryptographic analyses. Here we revisit these so-called…

Quantum Physics · Physics 2020-12-09 Keegan Yao , Walter O. Krawec , Jiadong Zhu

We introduce a general method for the construction of quasiprobability representations for arbitrary notions of quantum coherence. Our technique yields a nonnegative probability distribution for the decomposition of any classical state.…

Quantum Physics · Physics 2018-06-22 J. Sperling , I. A. Walmsley

B92-type and BB84-type quantum cryptography schemes using superposed states of the vacuum and single particle states which are robust against PNS attacks are studied. The number of securely transferred classical bits per particle (not per…

Quantum Physics · Physics 2007-09-27 Jae-Weon Lee , Jaewan Kim , Yong Wook Cheong , Hai-Woong Lee , Eok Kyun Lee

We propose a test for certifying the dimension of a quantum system: store in it a random $n$-bit string, in either the computational or the Hadamard basis, and later check that the string can be mostly recovered. The protocol tolerates…

Quantum Physics · Physics 2020-03-02 Rui Chao , Ben W. Reichardt

The quantum theory of decoherence plays an important role in a pragmatist interpretation of quantum theory. It governs the descriptive content of claims about values of physical magnitudes and offers advice on when to use quantum…

Quantum Physics · Physics 2012-07-30 Richard Healey

Recently, it has been argued that quantum mechanics is a complete theory, and that different quantum states do necessarily correspond to different elements of reality, under the assumptions that quantum mechanics is correct and that…

Quantum Physics · Physics 2015-06-23 Giancarlo Ghirardi , Raffaele Romano

We derive a new entropic quantum uncertainty relation involving min-entropy. The relation is tight and can be applied in various quantum-cryptographic settings. Protocols for quantum 1-out-of-2 Oblivious Transfer and quantum Bit Commitment…

Quantum Physics · Physics 2007-08-19 Ivan B. Damgaard , Serge Fehr , Renato Renner , Louis Salvail , Christian Schaffner