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We propose a numerical algorithm for finding optimal measurements for quantum-state discrimination. The theory of the semidefinite programming provides a simple check of the optimality of the numerically obtained results.

Quantum Physics · Physics 2016-09-08 M. Jezek , J. Rehacek , J. Fiurasek

The quantum capacity of a memoryless channel is often used as a single figure of merit to characterize its ability to transmit quantum information coherently. The capacity determines the maximal rate at which we can code reliably over…

Quantum Physics · Physics 2016-05-10 Marco Tomamichel , Mario Berta , Joseph M. Renes

Characterization of quantum systems from experimental data is a central problem in quantum science and technology. But which measurements should be used to gather data in the first place? While optimal measurement choices can be worked out…

Quantum Physics · Physics 2025-07-15 Jiaxin Huang , Yan Zhu , Giulio Chiribella , Ya-Dong Wu

In this review we discuss how channel simulation can be used to simplify the most general protocols of quantum parameter estimation, where unlimited entanglement and adaptive joint operations may be employed. Whenever the unknown parameter…

We propose a generalized form of entangled coherent states (ECS) and apply them in a multi-arm optical interferometer to estimate multiple phase shifts. We obtain the quantum Cramer-Rao bounds for both the linear and nonlinear…

Quantum Physics · Physics 2016-02-04 Jing Liu , Xiao-Ming Lu , Zhe Sun , Xiaoguang Wang

Quantum noise constitutes a fundamental obstacle to realizing practical quantum technologies. To address the pivotal challenge of identifying quantum systems least affected by noise, we introduce the purest quantum state identification,…

Quantum Physics · Physics 2025-09-24 Yingqi Yu , Honglin Chen , Jun Wu , Wei Xie , Xiangyang Li

In this paper, we prove a quantum union bound that is relevant when performing a sequence of binary-outcome quantum measurements on a quantum state. The quantum union bound proved here involves a tunable parameter that can be optimized, and…

Quantum Physics · Physics 2019-01-11 Samad Khabbazi Oskouei , Stefano Mancini , Mark M. Wilde

We review some partial results for two strictly related problems. The first problem consists in finding the optimal joint unitary transformation on system and ancilla which is the most efficient in programming any desired channel on the…

Quantum Physics · Physics 2007-05-23 Giacomo Mauro D'Ariano , Paolo Perinotti

Quantum-enhanced sensing promises to improve the performance of sensing tasks using non-classical probes and measurements that require far fewer scene-modulated photons than the best classical schemes, thereby granting…

Quantum Physics · Physics 2021-08-11 Michael R. Grace , Christos N. Gagatsos , Saikat Guha

Squeezed light enables quantum-enhanced phase estimation, with crucial applications in both fundamental physics and emerging technologies. To fully exploit the advantage provided by this approach, estimation protocols must remain optimal…

Quantum Physics · Physics 2025-10-17 Giorgio Minati , Enrico Urbani , Nicolò Spagnolo , Valeria Cimini , Fabio Sciarrino

Quantum metrology protocols are typically designed around the assumption that we have an abundance of measurement data, but recent practical applications are increasingly driving interest in cases with very limited data. In this regime the…

Quantum Physics · Physics 2019-04-18 Jesús Rubio , Jacob Dunningham

Quantum state tomography is an indispensable but costly part of many quantum experiments. Typically, it requires measurements to be carried in a number of different settings on a fixed experimental setup. The collected data is often…

Quantum Physics · Physics 2017-09-13 Jun Li , Shilin Huang , Zhihuang Luo , Keren Li , Dawei Lu , Bei Zeng

We present a general problem formulation for optimal parameter estimation based on quantized observations, with application to antenna array communication and processing (channel estimation, time-of-arrival (TOA) and direction-of-arrival…

Information Theory · Computer Science 2010-10-28 Amine Mezghani , Felix Antreich , Josef A. Nossek

Quantum phase estimation based on Gaussian states plays a crucial role in many application fields. In this paper, we study the precision bound for the scheme using two-mode squeezed Gaussian states. The quantum Fisher information is…

Quantum Physics · Physics 2024-11-27 Jian-Dong Zhang , Chuang Li , Lili Hou , Shuai Wang

We consider the problem of optimal probing of states of a channel by transmitter and receiver for maximizing rate of reliable communication. The channel is discrete memoryless (DMC) with i.i.d. states. The encoder takes probing actions…

Information Theory · Computer Science 2016-11-15 Himanshu Asnani , Haim Permuter , Tsachy Weissman

It is a well-known fact that the optimal POVM for quantum state tomography is the symmetric, informationally complete, positive operator valued measure (SIC-POVM). We investigate the same problem only in the case when there are some a…

Quantum Physics · Physics 2015-11-23 Dénes Petz , László Ruppert

Using convex optimization, we propose entanglement-assisted quantum error correction procedures that are optimized for given noise channels. We demonstrate through numerical examples that such an optimized error correction method achieves…

Quantum Physics · Physics 2010-10-28 Soraya Taghavi , Todd A. Brun , Daniel A. Lidar

We explore optical quantum engineering of phase-parameterized continuous-variable (CV) probe states to exploit nonclassical light to solve the problem of precise phase estimation. The optical interferometer consists of a single beam…

Quantum Physics · Physics 2026-03-11 Mikhail S. Podoshvedov , Sergey A. Podoshvedov

Quantum computers can be considered as a natural means for performing machine learning tasks for inherently quantum labeled data. Many quantum machine learning techniques have been developed for solving classification problems, such as…

Quantum Physics · Physics 2025-01-24 Andrey Kardashin , Yerassyl Balkybek , Vladimir V. Palyulin , Konstantin Antipin

Multiparameter quantum metrology is essential for a wide range of practical applications. However, simultaneously achieving the ultimate precision for all parameters, as prescribed by the quantum Cram\'er-Rao bound (QCRB), remains a…

Quantum Physics · Physics 2025-09-15 Minghao Mi , Ben Wang , Lijian Zhang