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Coherence is a defining property of quantum theory that accounts for quantum advantage in many quantum information tasks. Although many coherence quantifiers have been introduced in various contexts, the lack of efficient methods to…

Quantum Physics · Physics 2023-01-02 Sun Liang Liang , Yu Sixia

Quantum-enhanced measurements use highly non-classical quantum states in order to enhance the precision of the measurement of classical quantities, like the length of an optical cavity. The major goal is to beat the standard quantum limit…

Quantum Physics · Physics 2009-05-29 Daniel Braun , John Martin

The most basic scenario of quantum control involves the organized manipulation of pure dynamical states of the system by means of unitary transformations. Recently, Vilela Mendes and Mank'o have shown that the conditions for controllability…

Quantum Physics · Physics 2009-11-10 A. Mandilara , J. W. Clark

Quantum systems with dynamical symmetries have conserved quantities which are preserved under coherent controls. Therefore such systems can not be completely controlled by means of only coherent control. In particular, for such systems…

Quantum Physics · Physics 2023-07-17 Maria Elovenkova , Alexander Pechen

In the present paper, the trace distance is exposed within the quantum operations formalism. The definition of the trace distance in terms of a maximum over all quantum operations is given. It is shown that for any pair of different states,…

Quantum Physics · Physics 2009-11-13 A. E. Rastegin

Quantum coherence and quantum entanglement are two strong pillars in quantum information theory. We study here for the possibility of any connection between these two important aspects of quantum mechanics while studying the entanglement…

Quantum Physics · Physics 2022-03-25 Palash Garhwal , Pranav Chandhok , Satyabrata Adhikari

Artificial quantum systems with synthetic dimensions enable exploring novel quantum phenomena difficult to create in conventional materials. These synthetic degrees of freedom increase the system's dimensionality without altering its…

Quantum Physics · Physics 2025-08-11 Alexey Gorlach , Andrea Pizzi , Klaus Mølmer , Joseph Avron , Mordechai Segev , Ido Kaminer

The convergence of closed quantum systems in the degenerate cases to the desired target state by using the quantum Lyapunov control based on the average value of an imaginary mechanical quantity is studied. On the basis of the existing…

Systems and Control · Computer Science 2018-08-10 Shuang Cong , Fangfang Meng , Sen Kuang

Coherence and entanglement are fundamental properties of quantum systems, promising to power the near future quantum computers, sensors and simulators. Yet, their experimental detection is challenging, usually requiring full reconstruction…

Quantum Physics · Physics 2017-08-01 Graeme Smith , John A. Smolin , Xiao Yuan , Qi Zhao , Davide Girolami , Xiongfeng Ma

In this paper by using geometric techniques, we provide upper bounds for the Poincar\'e recurrence time of a quantum mixed state with discrete spectrum of energies. In the case of discrete but finite spectrum we obtain two type of upper…

Quantum Physics · Physics 2017-04-26 Vicent Gimeno , José M. Sotoca

Precisely characterizing and controlling realistic open quantum systems is one of the most challenging and exciting frontiers in quantum sciences and technologies. In this Letter, we present methods of approximately computing reachable sets…

Quantum Physics · Physics 2016-07-13 Jun Li , Dawei Lu , Zhihuang Luo , Raymond Laflamme , Xinhua Peng , Jiangfeng Du

We study the problem of driving an unknown initial mixed quantum state onto a known pure state without using unitary transformations. This can be achieved, in an efficient manner, with the help of sequential measurements on at least two…

Quantum Physics · Physics 2009-11-11 L. Roa , G. Olivares

It is not possible to obtain information about the observable properties of a quantum system without a physical interaction between the system and an external meter. This physical interaction is described by a unitary transformation of the…

Quantum Physics · Physics 2021-07-29 Tomonori Matsushita , Holger F. Hofmann

The uncertainty principle sets a bound on our ability to predict the measurement outcomes of two incompatible observables which are measured on a quantum particle simultaneously. In quantum information theory, the uncertainty principle can…

Quantum Physics · Physics 2019-12-03 H. Dolatkhah , S. Haseli , S. Salimi , A. s. Khorashad

Quantum information science explores the frontier of highly complex quantum states, the "entanglement frontier." This study is motivated by the observation (widely believed but unproven) that classical systems cannot simulate highly…

Quantum Physics · Physics 2012-11-13 John Preskill

Fundamental limits on the controllability of quantum mechanical systems are discussed in the light of quantum information theory. It is shown that the amount of entropy-reduction that can be extracted from a quantum system by feedback…

Quantum Physics · Physics 2016-09-08 Shiro Kawabata

We extend the work in New J. Phys. 19, 103015 (2017) by deriving a lower bound for the minimum time necessary to implement a unitary transformation on a generic, closed quantum system with an arbitrary number of classical control fields.…

Quantum Physics · Physics 2018-07-04 Juneseo Lee , Christian Arenz , Herschel Rabitz , Benjamin Russell

For a system randomly prepared in a number of quantum states, we present a lower bound for the distinguishability of the quantum states, that is, the success probability of determining the states in the form of entropy. When the states are…

Quantum Physics · Physics 2015-11-11 Seungho Yang , Jinhyoung Lee , Hyunseok Jeong

Decoherence is the process via which quantum superpositions states are reduced to classical mixtures. Decoherence has been predicted for relativistically accelerated quantum systems, however examples to date have involved restricting the…

Quantum Physics · Physics 2019-01-16 Daiqin Su , Timothy C. Ralph

We analyze the physics of optimal protocols to prepare a target state with high fidelity in a symmetrically coupled two-qubit system. By varying the protocol duration, we find a discontinuous phase transition, which is characterized by a…

Statistical Mechanics · Physics 2018-05-17 Marin Bukov , Alexandre G. R. Day , Phillip Weinberg , Anatoli Polkovnikov , Pankaj Mehta , Dries Sels