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One of the fundamental features of quantum mechanics is the superposition principle, a manifestation of which is embodied in quantum coherence. Coherence of a quantum state is invariably defined with respect to a preferred set of pointer…

Quantum Physics · Physics 2021-02-24 Chirag Srivastava , Sreetama Das , Ujjwal Sen

Quantum communication relies on optical implementations of channels, memories and repeaters. In the absence of perfect devices, a minimum requirement on real-world devices is that they preserve quantum correlations, meaning that they have…

Quantum Physics · Physics 2010-12-01 Nathan Killoran , Hauke Häseler , Norbert Lütkenhaus

Quantum computers are expected to offer substantial speedups over their classical counterparts and to solve problems that are intractable for classical computers. Beyond such practical significance, the concept of quantum computation opens…

Quantum Physics · Physics 2014-11-13 Stefanie Barz , Joseph F. Fitzsimons , Elham Kashefi , Philip Walther

Continuous-variable quantum cryptographic systems, including random number generation and key distribution, are often based on coherent detection. The essence of the security analysis lies in the randomness quantification. Previous analyses…

Quantum Physics · Physics 2018-10-24 Hongyi Zhou , Pei Zeng , Mohsen Razavi , Xiongfeng Ma

In this paper we consider quantum resources required to maximize the mean values of any nontrivial quantum observable. We show that the task of maximizing the mean value of an observable is equivalent to maximizing some form of coherence,…

Quantum Physics · Physics 2018-07-03 Kok Chuan Tan , Seongjeon Choi , Hyunseok Jeong

Quantum measurement is a class of quantum channels that sends quantum states to classical states. We set up resource theories of quantum coherence and quantum entanglement for quantum measurements and find relations between them. For this,…

Quantum Physics · Physics 2022-08-15 Ho-Joon Kim , Soojoon Lee

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

Quantum coherence is a fundamental manifestation of the quantum superposition principle. Recently, Baumgratz \emph{et al}. [Phys. Rev. Lett. \textbf{113}, 140401 (2014)] presented a rigorous framework to quantify coherence from the view of…

Quantum Physics · Physics 2017-08-02 Xianfei Qi , Ting Gao , Fengli Yan

Recent advances in quantum computing devices have brought attention to hybrid quantum-classical algorithms like the Variational Quantum Eigensolver (VQE) as a potential route to practical quantum advantage in chemistry. However, it is not…

Quantum coherence is one of the primary non-classical features of quantum systems. While protocols such as the Leggett-Garg inequality (LGI) and quantum tomography can be used to test for the existence of quantum coherence and dynamics in a…

Quantum Physics · Physics 2012-12-04 Che-Ming Li , Neill Lambert , Yueh-Nan Chen , Guang-Yin Chen , Franco Nori

Quantum tomography is the main method used to assess the quality of quantum information processing devices, but its complexity presents a major obstacle for the characterization of even moderately large systems. The number of experimental…

Quantum Physics · Physics 2015-03-19 Marcus P. da Silva , Olivier Landon-Cardinal , David Poulin

Quantum states may exhibit asymmetry with respect to the action of a given group. Such an asymmetry of states can be considered as a resource in applications such as quantum metrology, and it is a concept that encompasses quantum coherence…

Long-term quantum coherence constitutes one of the main challenges when engineering quantum devices. However, easily accessible means to quantify complex decoherence mechanisms are not readily available, nor are sufficiently stable systems.…

Quantum metrology promises higher precision measurements than classical methods. Entanglement has been identified as one of quantum resources to enhance metrological precision. However, generating entangled states with high fidelity…

Quantum Physics · Physics 2024-07-16 Jeongwoo Jae , Jiwon Lee , M. S. Kim , Kwang-Geol Lee , Jinhyoung Lee

Quantum systems, in general, output data that cannot be simulated efficiently by a classical computer, and hence is useful for solving certain mathematical problems and simulating quantum many-body systems. This also implies, unfortunately,…

Quantum Physics · Physics 2017-10-04 Keisuke Fujii , Masahito Hayashi

The quantum volume test is a full-system benchmark for quantum computers that is sensitive to qubit number, fidelity, connectivity, and other quantities believed to be important in building useful devices. The test was designed to produce a…

Quantum Physics · Physics 2022-05-11 Charles H. Baldwin , Karl Mayer , Natalie C. Brown , Ciarán Ryan-Anderson , David Hayes

We propose a method for characterizing a photodetector by directly reconstructing the Wigner functions of the detector's Positive-Operator-Value-Measure (POVM) elements. This method extends the works of S. Wallentowitz and Vogel [Phys. Rev.…

Quantum Physics · Physics 2019-09-25 Rajveer Nehra , Kevin Valson Jacob

Quantum coherence is a critical resource for many operational tasks. Understanding how to quantify and manipulate it also promises to have applications for a diverse set of problems in theoretical physics. For certain applications, however,…

Quantum Physics · Physics 2016-11-22 Iman Marvian , Robert W. Spekkens

The existence of incompatible measurements is a fundamental phenomenon having no explanation in classical physics. Intuitively, one considers given measurements to be incompatible within a framework of a physical theory, if their…

Quantum Physics · Physics 2015-08-27 Teiko Heinosaari , Jukka Kiukas , Daniel Reitzner

As the field of superconducting quantum computing approaches maturity, optimization of single-device performance is proving to be a promising avenue towards large-scale quantum computers. However, this optimization is possible only if…

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