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The quantum switch, the canonical example of a process with indefinite causal order, has been claimed to provide various advantages over processes with definite causal orders for some particular tasks in the field of quantum metrology. In…

Quantum Physics · Physics 2024-06-27 Raphaël Mothe , Cyril Branciard , Alastair A. Abbott

Identifying causal order from restricted projective data is generally nontrivial. When two quantum players interact only through an unobserved environment, the available local measurement statistics are typically not tomographically…

Quantum Physics · Physics 2026-05-07 Masahito Hayashi

We investigate the usefulness of side entanglement in discriminating between two generic qubit channels, {\ up to unitary pre- and post-processing,} and determine exact conditions under which it does enhance (as well as conditions under…

Quantum Physics · Physics 2023-10-25 Samad Khabbazi Oskouei , Stefano Mancini , Milajiguli Rexiti

Inferring the causal direction between two variables from their observation data is one of the most fundamental and challenging topics in data science. A causal direction inference algorithm maps the observation data into a binary value…

Machine Learning · Computer Science 2020-06-08 Yulai Zhang , Jiachen Wang , Gang Cen , Guiming Luo

A switched quantum channel with indefinite causal order is studied for the fundamental metrological task of phase estimation on a qubit unitary operator affected by quantum thermal noise. Specific capabilities are reported in the switched…

Quantum Physics · Physics 2022-11-04 Francois Chapeau-Blondeau

Identifying the precise moment when a quantum channel undergoes a change is a fundamental problem in quantum information theory. We study how accurately one can determine the time at which a channel transitions to another. We investigate…

Quantum Physics · Physics 2026-04-15 Kenji Nakahira

Originated from the superposition principle in quantum mechanics, coherence has been extensively studied as a kind important resource in quantum information processing. We investigate the distinguishability of coherence-breaking channels…

Quantum Physics · Physics 2019-09-04 Long-Mei Yang , Tao Li , Shao-Ming Fei , Zhi-Xi Wang

The present paper studies an operator norm that captures the distinguishability of quantum strategies in the same sense that the trace norm captures the distinguishability of quantum states or the diamond norm captures the…

Quantum Physics · Physics 2012-03-16 Gus Gutoski

We study the procedure for sequential unambiguous state discrimination. A qubit is prepared in one of two possible states, and measured by two observers Bob and Charlie sequentially. A necessary condition for the state to be unambiguously…

Quantum Physics · Physics 2013-12-02 Chao-Qian Pang , Fu-Lin Zhang , Li-Fang Xu , Mai-Lin Liang , Jing-Ling Chen

Quantum channel discrimination has been studied from an information-theoretic perspective, wherein one is interested in the optimal decay rate of error probabilities as a function of the number of unknown channel accesses. In this paper, we…

Quantum Physics · Physics 2025-10-28 Theshani Nuradha , Mark M. Wilde

Sequential methods for quantum hypothesis testing offer significant advantages over fixed-length approaches, which rely on a predefined number of state copies. Despite their potential, these methods remain underexplored for unambiguous…

Quantum Physics · Physics 2025-11-26 Jordi Pérez-Guijarro , Alba Pagès-Zamora , Javier R. Fonollosa

We propose new sequential sorting operations by adapting techniques and methods used for designing parallel sorting algorithms. Although the norm is to parallelize a sequential algorithm to improve performance, we adapt a contrarian…

Data Structures and Algorithms · Computer Science 2016-09-01 Alexandros V Gerbessiotis

Comparison of quantum objects is a task to determine whether two unknown quantum objects are the same or different. It is one of the most basic information processing tasks for learning property of quantum objects, and comparison of quantum…

Quantum Physics · Physics 2022-08-29 Yutaka Hashimoto , Akihito Soeda , Mio Murao

The data processing inequality is the most basic requirement for any meaningful measure of information. It essentially states that distinguishability measures between states decrease if we apply a quantum channel and is the centerpiece of…

Quantum Physics · Physics 2022-11-30 Christoph Hirche , Cambyse Rouzé , Daniel Stilck França

The problem of dephasing channel discrimination is addressed for finite-dimensional systems. In particular, the optimization with respect to input states without energy constraint is solved analytically for qubit, qutrit and ququart.…

Quantum Physics · Physics 2023-10-25 Milajiguli Rexiti , Laleh Memarzadeh , Stefano Mancini

Divergence chain rules for channels relate the divergence of a pair of channel inputs to the divergence of the corresponding channel outputs. An important special case of such a rule is the data-processing inequality, which tells us that if…

Quantum Physics · Physics 2024-05-21 Mario Berta , Marco Tomamichel

Quantum memories are a crucial precondition in many protocols for processing quantum information. A fundamental problem that illustrates this statement is given by the task of channel discrimination, in which an unknown channel drawn from a…

Quantum Physics · Physics 2026-01-28 Ties-A. Ohst , Shijun Zhang , Hai Chau Nguyen , Martin Plávala , Marco Túlio Quintino

This paper presents and analysis the common existing sequential pattern mining algorithms. It presents a classifying study of sequential pattern-mining algorithms into five extensive classes. First, on the basis of Apriori-based algorithm,…

Databases · Computer Science 2013-11-05 Thabet Slimani , Amor Lazzez

In distributed systems where strong consistency is costly when not impossible, causal consistency provides a valuable abstraction to represent program executions as partial orders. In addition to the sequential program order of each…

Distributed, Parallel, and Cluster Computing · Computer Science 2016-03-15 Matthieu Perrin , Achour Mostefaoui , Claude Jard

We investigate the performance of discrimination strategy in the comparison task of known quantum states. In the discrimination strategy, one infers whether or not two quantum systems are in the same state on the basis of the outcomes of…

Quantum Physics · Physics 2018-05-30 A. Hayashi , T. Hashimoto , M. Horibe