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We present a generic study of unambiguous discrimination between two mixed quantum states. We derive operational optimality conditions and show that the optimal measurements can be classified according to their rank. In Hilbert space…

Quantum Physics · Physics 2010-03-10 M. Kleinmann , H. Kampermann , D. Bruss

We address a broad class of optimization problems of finding quantum measurements, which includes the problems of finding an optimal measurement in the Bayes criterion and a measurement maximizing the average success probability with a…

Quantum Physics · Physics 2015-06-23 Kenji Nakahira , Kentaro Kato , Tsuyoshi Sasaki Usuda

Information processing, quantum or classical, relies on channels transforming multiple input states to different corresponding outputs. Previous research has established bounds on the thermodynamic resources required for such operations,…

Quantum Physics · Physics 2024-05-22 Joe Dunlop , Federico Cerisola , Jorge Tabanera-Bravo , Janet Anders

The complexity of large-scale 6G-and-beyond networks demands innovative approaches for multi-objective optimization over vast search spaces, a task often intractable. Quantum computing (QC) emerges as a promising technology for efficient…

Networking and Internet Architecture · Computer Science 2025-09-10 Sebastian Macaluso , Giovanni Geraci , Elías F. Combarro , Sergi Abadal , Ioannis Arapakis , Sofia Vallecorsa , Eduard Alarcón

Universal fault-tolerant quantum computers will require error-free execution of long sequences of quantum gate operations, which is expected to involve millions of physical qubits. Before the full power of such machines will be available,…

The quantum computer is supposed to process information by applying unitary transformations to the complex amplitudes defining the state of N qubits. A useful machine needing N=1000 or more, the number of continuous parameters describing…

Quantum Physics · Physics 2014-09-23 M. I. Dyakonov

A generalized universal quantum cloning machine is proposed which allows the input to be arbitrary states in symmetric subspace. And it reduces to the universal quantum cloning machine (UQCM) if the input are identical pure states. The…

Quantum Physics · Physics 2007-05-23 Heng Fan , Keiji Matsumoto , Xiang-Bin Wang , Hiroshi Imai , Miki Wadati

In this study the determinant of the average quadratic error matrix is used as the measure of state estimation efficiency. This quantity is easily computable in some cases, so it gives us a reasonable tool to find optimal measurement setup…

Quantum Physics · Physics 2012-01-10 Denes Petz , Laszlo Ruppert

Quantum computing has shown tremendous promise in addressing complex computational problems, yet its practical realization is hindered by the limited availability of qubits for computation. Recent advancements in quantum hardware have…

Quantum Physics · Physics 2023-11-22 Kun Fang , Munan Zhang , Ruqi Shi , Yinan Li

Uhlmann's theorem is a central result in quantum information theory, which associates the closeness of two quantum states with that of their purifications. The theorem also well characterizes a fundamental task: how close a pure quantum…

Quantum Physics · Physics 2025-11-04 Takeru Utsumi , Yoshifumi Nakata , Qisheng Wang , Ryuji Takagi

We present optimal and minimal measurements on identical copies of an unknown state of a qubit when the quality of measuring strategies is quantified with the gain of information (Kullback of probability distributions). We also show that…

Quantum Physics · Physics 2009-10-31 Rolf Tarrach , Guifre Vidal

Quantum circuit optimization - the process of transforming a quantum circuit into an equivalent one with reduced time and space requirements - is crucial for maximizing the utility of current and near-future quantum devices. While most…

Quantum Physics · Physics 2026-01-23 Marcin Szyniszewski , Aleks Kissinger , Noah Linden , Paul Skrzypczyk

Quantum state purification, which operates not by identifying and correcting specific errors but by repeatedly projecting multiple noisy copies onto special subspaces, provides a syndrome-free alternative to quantum error correction.…

Quantum Physics · Physics 2026-04-17 Xing-Chen Guo , Benchi Zhao , Xin Wang

We study an optimum measurement for quantum state discrimination, which maximizes the probability of correct results when the probability of inconclusive results is fixed at a given value. The measurement describes minimum-error…

Quantum Physics · Physics 2012-09-26 Ulrike Herzog

Machine learning is a fascinating and exciting field within computer science. Recently, this excitement has been transferred to the quantum information realm. Currently, all proposals for the quantum version of machine learning utilize the…

Quantum Physics · Physics 2017-02-28 Hoi-Kwan Lau , Raphael Pooser , George Siopsis , Christian Weedbrook

The optimal quantum control theory is employed to determine electric pulses capable of producing quantum gates with high fidelity (higher than 0.9997). Particularly, these quantum gates were chosen to perform the permutation algorithm (Z.…

Quantum Physics · Physics 2018-03-28 C. M. Rivera-Ruiz , E. F. de Lima , F. F. Fanchini , V. Lopez-Richard , L. K. Castelano

The problem of discriminating with minimum error between two mixed quantum states is reviewed, with emphasize on the detection operators necessary for performing the measurement. An analytical result is derived for the minimum probability…

Quantum Physics · Physics 2009-11-10 Ulrike Herzog

Measurement incompatibility is a cornerstone of quantum mechanics. In the context of estimating multiple parameters of a quantum system, this manifests as a fundamental trade-off between the precisions with which different parameters can be…

Quantum Physics · Physics 2025-11-11 Simon K. Yung , Aritra Das , Jun Suzuki , Ping Koy Lam , Jie Zhao , Lorcán O. Conlon , Syed M. Assad

Qudit-based quantum computation offers unique advantages over qubit-based systems in terms of noise mitigation capabilities as well as algorithmic complexity improvements. However, the software ecosystem for multi-state quantum systems is…

Quantum Physics · Physics 2023-11-14 Daniel Volya , Prabhat Mishra

Thermodynamics is traditionally concerned with systems comprised of a large number of particles. Here we present a framework for extending thermodynamics to individual quantum systems, including explicitly a thermal bath and work-storage…

Quantum Physics · Physics 2014-09-29 Paul Skrzypczyk , Anthony J. Short , Sandu Popescu