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A new family of polarized ensembles of random pure states is presented. These ensembles are obtained by linear superposition of two random pure states with suitable distributions, and are quite manageable. We will use the obtained results…

Mathematical Physics · Physics 2013-07-25 F. D. Cunden , P. Facchi , G. Florio

Quantum coherence is important in quantum mechanics, and its essence is from superposition principle. We study the coherence of any two pure states and that of their arbitrary superposition, and obtain the relationship between them. In the…

Quantum Physics · Physics 2016-05-25 Qiu-Ling Yue , Chao-Hua Yu , Feng Liu , Xiao-Li Wang , Fei Gao , Qiao-Yan Wen

We state a quantum version of Bayes's rule for statistical inference and give a simple general derivation within the framework of generalized measurements. The rule can be applied to measurements on N copies of a system if the initial state…

Quantum Physics · Physics 2009-11-06 Ruediger Schack , Todd A. Brun , Carlton M. Caves

The resources needed to conventionally characterize a quantum system are overwhelmingly large for high- dimensional systems. This obstacle may be overcome by abandoning traditional cornerstones of quantum measurement, such as general…

Quantum Physics · Physics 2016-05-17 Gregory A. Howland , Samuel H. Knarr , James Schneeloch , Daniel J. Lum , John C. Howell

Quantum coherence is the outcome of the superposition principle. Recently, it has been theorized as a quantum resource, and is the premise of quantum correlations in multipartite systems. It is therefore interesting to study the coherence…

Quantum Physics · Physics 2017-02-21 Asutosh Kumar

We have investigated the problem of discriminating between nonorthogonal quantum states with least probability of error. We have determined that the best strategy for some sets of states is to make no measurement at all, and simply to…

Quantum Physics · Physics 2009-11-07 Kieran Hunter

Random matrix theory is used to represent generic loss of coherence of a fixed central system coupled to a quantum-chaotic environment, represented by a random matrix ensemble, via random interactions. We study the average density matrix…

Quantum Physics · Physics 2009-09-30 T. Gorin , C. Pineda , H. Kohler , T. H. Seligman

It is a fundamental consequence of the superposition principle for quantum states that there must exist non-orthogonal states, that is states that, although different, have a non-zero overlap. This finite overlap means that there is no way…

Quantum Physics · Physics 2008-10-14 Stephen M. Barnett , Sarah Croke

We consider quantum enhanced measurements with initially mixed states. We show very generally that for any linear propagation of the initial state that depends smoothly on the parameter to be estimated, the sensitivity is bound by the…

Quantum Physics · Physics 2015-05-18 Daniel Braun

We investigate the generic aspects of quantum coherence guided by the concentration of measure phenomenon. We find the average relative entropy of coherence of pure quantum states sampled randomly from the uniform Haar measure and show that…

Quantum Physics · Physics 2016-03-30 Uttam Singh , Lin Zhang , Arun Kumar Pati

Quantum superposition says that any physical system simultaneously exists in all of its possible states, the number of which is exponential in the number of entities composing the system. The strength of presence of each possible state in…

Neural and Evolutionary Computing · Computer Science 2017-07-19 Gerard J. Rinkus

It is well-known that pure quantum states are typically almost maximally entangled, and thus have close to maximally mixed subsystems. We consider whether this is true for probabilistic theories more generally, and not just for quantum…

Quantum Physics · Physics 2012-11-13 Markus P. Müller , Oscar C. O. Dahlsten , Vlatko Vedral

The statistical problem of the distribution of $s$ quanta of equal energy $\epsilon_0$ and total energy $E$ among $N$ distinguishable particles is resolved using the conventional theory based on Boltzmann's principle of equal probabilities…

Quantum Physics · Physics 2021-11-18 Michalis Psimopoulos , Emilie Dafflon

The quantum prepare-and-measure scenario has been studied under various physical assumptions on the emitted states. Here, we first discuss how different assumptions are conceptually and formally related. We then identify one that can serve…

Quantum Physics · Physics 2025-02-19 Jef Pauwels , Stefano Pironio , Armin Tavakoli

The class of incoherent operations induces a pre-order on the set of quantum pure states, defined by the possibility of converting one state into the other by transformations within the class. We prove that if two $n$-dimensional pure…

Quantum Physics · Physics 2021-07-02 Fabio Deelan Cunden , Paolo Facchi , Giuseppe Florio , Giovanni Gramegna

In this paper, we consider the problem of unambiguous discrimination between a set of mixed quantum states. We first divide the density matrix of each mixed state into two parts by the fact that it comes from ensemble of pure quantum…

Quantum Physics · Physics 2007-05-23 Chi Zhang , Yuan Feng , Ming Sheng Ying

A simple method is proposed to prepare conveniently the effective pure state |00...0><0...00| with any number of qubits in a quantum ensemble. The preparation is based on the temporal averaging (Knill, Chuang, and Laflamme, Phys.Rev.A 57,…

Quantum Physics · Physics 2007-05-23 Xijia Miao

The quantum density matrix generalises the classical concept of probability distribution to quantum theory. It gives the complete description of a quantum state as well as the observable quantities that can be extracted from it. Its…

Quantum Physics · Physics 2023-08-31 Apoorva D. Patel

The density matrix formalism which is widely used in the theory of measurements, quantum computing, quantum description of chemical and biological systems always imply the averaging over the states of the environment. In practice this is…

Quantum Physics · Physics 2007-05-23 M. V. Altaisky

We theoretically derive the probability densities of the entanglement measures of a pure non-ergodic many-body state, represented in a bipartite product basis and with its reduced density matrix described by a generalized, multi-parametric…

Quantum Physics · Physics 2024-12-11 Devanshu Shekhar , Pragya Shukla