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Quantum computation has been growing rapidly in both theory and experiments. In particular, quantum computing devices with a large number of qubits have been developed by IBM, Google, IonQ, and others. The current quantum computing devices…

Quantum Physics · Physics 2021-02-10 Rishabh Gupta , Rongxin Xia , Raphael D. Levine , Sabre Kais

The optimal estimation of a quantum mechanical 2-state system (qubit) - with N identically prepared qubits available - is obtained by measuring all qubits simultaneously in an entangled basis. We report the experimental estimation of qubits…

Quantum Physics · Physics 2007-05-23 Th. Hannemann , D. Reiss , Ch. Balzer , W. Neuhauser , P. E. Toschek , Ch. Wunderlich

Measuring the state of a quantum system is a fundamental process in quantum mechanics and plays an essential role in quantum information and quantum technologies. One method to measure a quantum observable is to sort the system in different…

Quantum Physics · Physics 2016-05-05 Radu Ionicioiu

We consider a hypothetical apparatus that implements measurements for arbitrary 4-local quantum observables A on n qubits. The apparatus implements the ``measurement algorithm'' after receiving a classical description of A. We show that a…

Quantum Physics · Physics 2007-05-23 Pawel Wocjan , Dominik Janzing , Thomas Decker , Thomas Beth

Characterization of quantum processes is a preliminary step necessary in the development of quantum technology. The conventional method uses standard quantum process tomography, which requires $d^2$ input states and $d^4$ quantum…

Quantum Physics · Physics 2020-02-26 Zhibo Hou , Jun-Feng Tang , Christopher Ferrie , Guo-Yong Xiang , Chuan-Feng Li , Guang-Can Guo

The ability to perform a universal set of quantum operations based solely on static resources and measurements presents us with a strikingly novel viewpoint for thinking about quantum computation and its powers. We consider the two major…

Quantum Physics · Physics 2007-05-23 Panos Aliferis , Debbie W. Leung

In Ref. [Phys. Rev. A 100, 062317 (2019)], the authors reported an algorithm to implement, in a circuit-based quantum computer, a general quantum measurement (GQM) of a two-level quantum system, a qubit. Even though their algorithm seems…

Quantum Physics · Physics 2023-02-10 Douglas F. Pinto , Marcelo S. Zanetti , Marcos L. W. Basso , Jonas Maziero

Recently, a technique known as quantum symmetry test has gained increasing attention for detecting bipartite entanglement in pure quantum states. In this work we show that, beyond qualitative detection, a family of well-defined measures of…

Quantum Physics · Physics 2025-11-12 Xiaoyu Liu , Jordi Tura , Albert Rico

We present a detailed account of quantum state estimation by joint maximization of the likelihood and the entropy. After establishing the algorithms for both perfect and imperfect measurements, we apply the procedure to data from simulated…

We investigate the optimal measurement strategy for state discrimination of the trine ensemble of qubit states prepared with arbitrary prior probabilities. Our approach generates the minimum achievable probability of error and also the…

Quantum Physics · Physics 2018-03-12 Graeme Weir , Catherine Hughes , Stephen M. Barnett , Sarah Croke

The initial state creation is a starting point of many quantum algorithms and usually is considered as a separate subroutine not included into the algorithm itself. There are many algorithms aimed on creation of special class of states. Our…

Quantum Physics · Physics 2025-05-01 Alexander I. Zenchuk , Wentao Qi , Junde Wu

We study the problem of mapping an unknown mixed quantum state onto a known pure state without the use of unitary transformations. This is achieved with the help of sequential measurements of two non-commuting observables only. We show that…

Quantum Physics · Physics 2009-11-11 L. Roa , M. L. Ladron de Guevara , A. Delgado , A. Klimov

A software product line models the variability of highly configurable systems. Complete exploration of all valid configurations (the configuration space) is infeasible as it grows exponentially with the number of features in the worst case.…

Quantum Physics · Physics 2023-07-28 Joshua Ammermann , Tim Bittner , Domenik Eichhorn , Ina Schaefer , Christoph Seidl

In quantum systems, the measurement of operators and the measurement of the quantum states of the system are very challenging tasks. In this Letter, we propose a method to obtain the average value of one operator in a certain state by…

A projective measurement of energy (PME) on a quantum system is a quantum measurement, determined by the Hamiltonian of the system. PME protocols exist when the Hamiltonian is given in advance. Unknown Hamiltonians can be identified by…

Quantum Physics · Physics 2015-05-20 Shojun Nakayama , Akihito Soeda , Mio Murao

We consider the apparatus in a quantum measurement process to be in a mixed state. We propose a simple upper bound on the probability of correctly distinguishing any number of mixed states. We use this to derive fundamental bounds on the…

Quantum Physics · Physics 2007-05-23 S. Bose , V. Vedral

Among the surprising features of quantum measurements, the problem of distinguishing and antidistinguishing general quantum measurements is fundamentally appealing. Unlike classical systems, quantum theory offers entangled states and…

Quantum Physics · Physics 2025-08-19 Satyaki Manna , Sneha Suresh , Manan Singh Kachhawaha , Debashis Saha

We introduce a measure Q of bipartite quantum correlations for arbitrary two-qubit states, expressed as a state-independent function of the density matrix elements. The amount of quantum correlations can be quantified experimentally by…

Quantum Physics · Physics 2012-04-16 Davide Girolami , Gerardo Adesso

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

In this work we investigate how to quantify the coherence of quantum measurements. First, we establish a resource theoretical framework to address the coherence of measurement and show that any statistical distance can be adopted to define…

Quantum Physics · Physics 2020-08-11 Kyunghyun Baek , Adel Sohbi , Jaehak Lee , Jaewan Kim , Hyunchul Nha