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The dynamics induced while controlling quantum systems by optimally shaped laser pulses have often been difficult to understand in detail. A method is presented for quantifying the importance of specific sequences of quantum transitions…

Quantum Physics · Physics 2009-11-07 Eric Dennis , Herschel Rabitz

Determining the state of a quantum system is a consuming procedure. For this reason, whenever one is interested only in some particular property of a state, it would be desirable to design a measurement setup that reveals this property with…

Quantum Physics · Physics 2017-06-02 Claudio Carmeli , Teiko Heinosaari , Jussi Schultz , Alessandro Toigo

In this paper we describe in detail and generalize a method for quantum process tomography that was presented in [A. Bendersky, F. Pastawski, J. P. Paz, Physical Review Letters 100, 190403 (2008)]. The method enables the efficient…

Quantum Physics · Physics 2015-05-13 Ariel Bendersky , Fernando Pastawski , Juan Pablo Paz

Frequent observation of a quantum system leads to quantum Zeno physics, where the system evolution is constrained to states commensurate with the measurement outcome. We show that, more generally, the system can evolve between such states…

Quantum Physics · Physics 2016-08-03 Thomas J. Elliott , Vlatko Vedral

A brief review is given of the present state of an approach to consistency between basic quantum mechanics and a unique macroscopic reality, with no assumption of branching in the state of the universe. The main new idea consists in the…

Quantum Physics · Physics 2013-02-08 Roland Omnes

Estimating properties of a quantum state is an indispensable task in various applications of quantum information processing. To predict properties in the post-processing stage, it is inherent to first perceive the quantum state with a…

Quantum Physics · Physics 2024-02-29 Yinfei Li , Sanjib Ghosh , Jiangwei Shang , Qihua Xiong , Xiangdong Zhang

Eigenvalues of a density matrix characterize well the quantum state's properties, such as coherence and entanglement. We propose a simple method to determine all the eigenvalues of an unknown density matrix of a finite-dimensional system in…

Quantum Physics · Physics 2014-01-24 Tohru Tanaka , Yukihiro Ota , Mitsunori Kanazawa , Gen Kimura , Hiromichi Nakazato , Franco Nori

The state of a quantum system, consisting of two distinct subsystems, is called separable if it can be prepared by two distant experimenters who receive instructions from a common source, via classical communication channels. A necessary…

Quantum Physics · Physics 2009-10-30 Asher Peres

We present a technique for enhancing the estimation of quantum state properties by incorporating approximate prior knowledge about the quantum state of interest. This method involves performing randomized measurements on a quantum processor…

It is shown how, given a "probability data table" for a quantum or classical system, the representation of states and measurement outcomes as vectors in a real vector space follows in a natural way. Some properties of the resulting sets of…

Quantum Physics · Physics 2007-05-23 Piero G. L. Mana

A usual assumption in quantum estimation is that the unknown parameter labels the possible states of the system, while it influences neither the sample space of outcomes nor the measurement aimed at extracting information on the parameter…

Quantum Physics · Physics 2017-01-18 Luigi Seveso , Matteo A. C. Rossi , Matteo G. A. Paris

For theoretical approach of quantum measurements it is proposed a set of reconsidered conjectures. The proposed approach implies linear functional transformations for probability density and current but preserves the expressions for…

Quantum Physics · Physics 2007-05-23 S. Dumitru

By repeated trials, one can determine the fairness of a classical coin with a confidence which grows with the number of trials. A quantum coin can be in a superposition of heads and tails and its state is most generally a density matrix.…

Quantum Physics · Physics 2020-04-22 Arpita Maitra , Joseph Samuel , Supurna Sinha

Quantifying coherence is an essential endeavor for both quantum mechanical foundations and quantum technologies. We present a bona fide measure of quantum coherence by utilizing the Tsallis relative operator $(\alpha, \beta)$-entropy. We…

Quantum Physics · Physics 2023-06-22 Meng-Li Guo , Zhi-Xiang Jin , Jin-Min Liang , Bo Li , Shao-Ming Fei

In textbooks, ideal quantum measurements are described in terms of the tested system only by the collapse postulate and Born's rule. This level of description offers a rather flexible position for the interpretation of quantum mechanics.…

Quantum Physics · Physics 2017-09-28 Theo M. Nieuwenhuizen , Marti Perarnau-Llobet , Roger Balian

The characterization of physical systems requires a comprehensive understanding of quantum effects. One aspect is a proper quantification of the strength of such quantum phenomena. Here, a general convex ordering of quantum states will be…

Quantum Physics · Physics 2015-06-24 J. Sperling , W. Vogel

The paper proves that quantum mechanics is compatible with the constructive realism of modern philosophy of science. The proof is based on the observation that properties of quantum systems that are uniquely determined by their preparations…

Quantum Physics · Physics 2013-06-17 Petr Hajicek

A unified conceptual foundation of classical and quantum physics is given, free of undefined terms. Ensembles are defined by extending the `probability via expectation' approach of Whittle to noncommuting quantities. This approach carries…

Quantum Physics · Physics 2007-05-23 Arnold Neumaier

Applications of quantum mechanics have led to many successful predictions and explanations of puzzling phenomena, and we now apply quantum mechanics to gain, process, and communicate information in novel ways. We can understand quantum…

Quantum Physics · Physics 2026-04-03 Richard Healey

In quantum mechanics, we define the measuring system $M$ in a selective measurement by two conditions. Firstly, when we define the measured system $S$ as the system in which the non-selective measurement part acts, $M$ is independent from…

Quantum Physics · Physics 2021-09-28 Eiji Konishi
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