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We propose a general framework for solving quantum state estimation problems using the minimum relative entropy criterion. A convex optimization approach allows us to decide the feasibility of the problem given the data and, whenever…

Quantum Physics · Physics 2013-01-29 Mattia Zorzi , Francesco Ticozzi , Augusto Ferrante

The relational interpretation (or RQM, for Relational Quantum Mechanics) solves the measurement problem by considering an ontology of sparse relative events, or "facts". Facts are realized in interactions between any two physical systems…

Quantum Physics · Physics 2021-10-04 Carlo Rovelli

We explore the sense in which the state of a physical system may or may not be regarded (an) observable in quantum mechanics. Simple and general arguments from various lines of approach are reviewed which demonstrate the following no-go…

Quantum Physics · Physics 2007-05-23 P. Busch

We can recognize two modes in which 'quantum appears' in macro domains: (i) a 'micro-physical appearance', where quantum laws are assumed to be universal and they are transferred from the micro to the macro level if suitable 'quantum…

History and Philosophy of Physics · Physics 2015-12-31 Diederik Aerts , Sandro Sozzo

It is nowadays accepted that truly quantum correlations can exist even in the absence of entanglement. For the case of symmetric states, a physically trivial unitary transformation can alter a quantum state from entangled to separable and…

Quantum Physics · Physics 2022-02-24 Aaron Z. Goldberg , Markus Grassl , Gerd Leuchs , Luis L. Sánchez-Soto

In recent years, several measures have been proposed for characterizing the coherence of a given quantum state. We derive several results that illuminate how these measures behave when restricted to pure states. Notably, we present an…

Quantum Physics · Physics 2016-10-26 Jianxin Chen , Shane Grogan , Nathaniel Johnston , Chi-Kwong Li , Sarah Plosker

We establish a lower bound on the quantum coherence of an arbitrary quantum state in arbitrary dimension, using a noncommutativity estimator of an arbitrary observable of sub-unit norm, where the estimator is the commutator of the…

Quantum Physics · Physics 2022-06-22 Tanaya Ray , Ahana Ghoshal , Arun Kumar Pati , Ujjwal Sen

The status of locality in quantum mechanics is analyzed from a nonstandard point of view. It is assumed that quantum states are relative, they depend on and are defined with respect to some bigger physical system which contains the former…

Quantum Physics · Physics 2007-05-23 Gyula Bene

A central problem in quantum resource theory is to give operational meaning to quantum resources that can provide clear advantages in certain physical tasks compared to the convex set of resource-free states. We propose to extend this basic…

Quantum Physics · Physics 2024-12-30 Sunho Kim , Chunhe Xiong , Junde Wu

Whether the complex numbers of standard quantum theory are experimentally indispensable has remained open for decades. Real quantum theory (RQT), obtained by replacing complex amplitudes with real ones while retaining the usual…

Quantum Physics · Physics 2026-03-20 Timothée Hoffreumon , Mischa P. Woods

A novel no-go theorem is presented which sets a bound upon the extent to which '\Psi-epistemic' interpretations of quantum theory are able to explain the overlap between non-orthogonal quantum states in terms of an experimenter's ignorance…

Quantum Physics · Physics 2013-05-23 O. J. E. Maroney

Quantum coherence as an important quantum resource plays a key role in quantum theory. In this paper, using entropy-based measures, we investigate the relations between quantum correlated coherence, which is the coherence between subsystems…

Quantum Physics · Physics 2017-03-03 Xiao-Li Wang , Qiu-Ling Yue , Chao-Hua Yu , Fei Gao , Su-Juan Qin

Exploiting the tension between the two dynamics of quantum theory (QT) in the Wigner's Friend thought experiment, we point out that the standard QT leads to inconsistency in observed probabilities of measurement outcomes between two…

Quantum Physics · Physics 2023-03-07 Shubhayan Sarkar , Debashis Saha

Relational quantum mechanics (RQM) proposes an ontology of relations between physical systems, where any system can serve as an `observer' and any physical interaction between systems counts as a `measurement'. Quantities take unique values…

Quantum Physics · Physics 2021-12-30 Jacques L. Pienaar

A projective quantum logic in terms of relative states is developed, emphasizing the importance of information transfer between a system under study and its environment. The need for accounting for the historical evolution of system is…

Quantum Physics · Physics 2026-05-13 Martin Paul Vaughan

We consider the relative entropy between vacuum states of two different theories: a conformal field theory (CFT), and the CFT perturbed by a relevant operator. By restricting both states to the null Cauchy surface in the causal domain of a…

High Energy Physics - Theory · Physics 2017-04-05 Horacio Casini , Eduardo Teste , Gonzalo Torroba

In the asymptotic theory of quantum hypothesis testing, the minimal error probability of the first kind jumps sharply from zero to one when the error exponent of the second kind passes by the point of the relative entropy of the two states…

Quantum Physics · Physics 2014-02-28 Ke Li

One of the key tasks in physics is to perform measurements in order to determine the state of a system. Often, measurements are aimed at determining the values of physical parameters, but one can also ask simpler questions, such as "is the…

Quantum Physics · Physics 2021-07-01 Jan de Boer , Victor Godet , Jani Kastikainen , Esko Keski-Vakkuri

State representations summarize our knowledge about a system. When unobservable quantities are introduced the state representation is typically no longer unique. However, this non-uniqueness does not affect subsequent inferences based on…

Quantum Physics · Physics 2009-11-10 Kae Nemoto , Samuel L. Braunstein

We prove tight lower bounds for the following variant of the counting problem considered by Aaronson, Kothari, Kretschmer, and Thaler (2020). The task is to distinguish whether an input set $x\subseteq [n]$ has size either $k$ or…

Quantum Physics · Physics 2024-05-08 Aleksandrs Belovs , Ansis Rosmanis