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Quantum conditional entropies play a fundamental role in quantum information theory. In quantum key distribution, they are exploited to obtain reliable lower bounds on the secret-key rates in the finite-size regime, against collective…

Quantum Physics · Physics 2026-03-05 Gabriele Staffieri , Giovanni Scala , Cosmo Lupo

Device-independent quantum key distribution (DI-QKD) provides the gold standard for secure key exchange. Not only it allows for information-theoretic security based on quantum mechanics, but it relaxes the need to physically model the…

In a recent work [A. Aloy et al. arXiv:1807:06027 (2018)] we have considered the characterization of entanglement depth, from a device-independent perspective, in a quantum many-body system. We have shown that the inequalities introduced in…

The quantum cryptographic conferencing (QCC) protocol, which distributes identical secure keys to user groups, is a crucial component of the quantum network. Previous experimental works have implemented the measurement-device-independent…

Quantum Physics · Physics 2026-02-25 Yifeng Du , Yang Hu , Yufeng Liu , Wenhan Yan , Jinghao Zhang , Shining Zhu , Xiao-Song Ma

Measurement-device-independent (MDI) method is a way to solve all detector side-channel attacks in quantum key distribution (QKD). However, very little work has been done on experimentally feasible qudit-based MDI-QKD scheme although the…

Quantum Physics · Physics 2016-08-31 H. F. Chau , Cardythy Wong , Qinan Wang , Tieqiao Huang

Quantum Key Distribution (QKD) is based on the laws of quantum mechanics to enable provably secure communication. Despite its theoretical security promise, practical QKD systems are vulnerable to serious attacks, including side-channel…

Quantum Physics · Physics 2025-05-21 Syed M. Arslan , Saif Al-Kuwari , M. T. Rahim , Hashir Kuniyal

We develop a quantum relative entropy method for the mean-field limit of quantum many-body systems. For closed systems governed by the von Neumann equation, we prove a quantitative stability estimate between the $N$-body density matrix and…

Mathematical Physics · Physics 2026-05-12 Gaoyue Guo , Hao Liang , Zhenfu Wang

Measurement-device-independent quantum key distribution (MDI-QKD) with weak coherent sources has been widely and meticulously analyzed. However, the analysis for MDI-QKD with spontaneous parametric-down-conversion sources (SPDCS) is…

Quantum Physics · Physics 2014-03-10 Chun Zhou , Wan-Su Bao , Wei Chen , Hong-Wei Li , Zhen-Qiang Yin , Yang Wang , Zheng-Fu Han

We propose an improved bound for the difference between phase and bit error rate in measurement-device-independent quantum key distribution with uncharacterized qubits. We show by simulations that the bound considerably increases the final…

Quantum Physics · Physics 2017-08-02 Won-Young Hwang , Hong-Yi Su , Joonwoo Bae

Reference-Frame-Independent Quantum Key Distribution (RFI-QKD) provides a practical way to generate secret keys between two remote parties without sharing common reference frames. On the other hand, Measurement-Device-Independent QKD…

The von Neumann and quantum R\'enyi entropies characterize fundamental properties of quantum systems and lead to theoretical and practical applications in many fields. Quantum algorithms for estimating quantum entropies, using a quantum…

Quantum Physics · Physics 2023-10-13 Youle Wang , Benchi Zhao , Xin Wang

This thesis synthesizes probability and entropic inference with Quantum Mechanics (QM) and quantum measurement [1-6]. It is shown that the standard and quantum relative entropies are tools designed for the purpose of updating probability…

Quantum Physics · Physics 2018-04-25 Kevin Vanslette

We provide two new methods for computing lower bounds of eigenvalues of symmetric elliptic second-order differential operators with mixed boundary conditions of Dirichlet, Neumann, and Robin type. The methods generalize ideas of Weinstein's…

Numerical Analysis · Mathematics 2017-05-30 Tomáš Vejchodský , Ivana Šebestová

The measurement-device-independent quantum key distribution (MDI-QKD) protocol is proposed to remove the detector side channel attacks, while its security relies on the assumption that the encoding systems are perfectly characterized. In…

We propose a reference-frame-independent measurement-device-independent quantum key distribution with uncharacterized quantum bits. We show the security of the protocol. The protocol can also be useful for a channel that has a very low bit…

Quantum Physics · Physics 2018-10-17 Won-Young Hwang

We present a device-independent randomness expansion protocol, involving only a constant number of non-signaling quantum devices, that achieves \emph{infinite expansion}: starting with $m$ bits of uniform private randomness, the protocol…

Quantum Physics · Physics 2014-04-03 Matthew Coudron , Henry Yuen

Using the graphical calculus and integration techniques introduced by the authors, we study the statistical properties of outputs of products of random quantum channels for entangled inputs. In particular, we revisit and generalize models…

Quantum Physics · Physics 2012-02-17 Benoit Collins , Ion Nechita

Quantum relative entropy, a quantum generalization of the renowned Kullback-Leibler divergence, serves as a fundamental measure of the distinguishability between quantum states and plays a pivotal role in quantum information science.…

Quantum Physics · Physics 2025-10-02 Yuchen Lu , Kun Fang

Distributed inner product estimation (DIPE) is a fundamental task in quantum information, aiming to estimate the inner product between two unknown quantum states prepared on distributed quantum platforms. Existing rigorous sample complexity…

Quantum Physics · Physics 2026-02-03 Congcong Zheng , Kun Wang , Xutao Yu , Ping Xu , Zaichen Zhang

In this work we investigate a binned version of Quantum Phase Estimation (QPE) set out by [Somma 2019] and known as the Quantum Eigenvalue Estimation Problem (QEEP). Specifically, we determine whether the circuit decomposition techniques we…

Quantum Physics · Physics 2021-10-27 Laura Clinton , Johannes Bausch , Joel Klassen , Toby Cubitt