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According to the quantum de Finetti theorem, if the state of an N-partite system is invariant under permutations of the subsystems then it can be approximated by a state where almost all subsystems are identical copies of each other,…

Quantum Physics · Physics 2009-03-19 Renato Renner , J. Ignacio Cirac

Using the monotonity of relative entropy of composite quantum systems we obtain new entropic inequalities for arbitrary density matrices of single qudit states. Example of qutrit state inequalities and the "qubit portrait" bound for the…

Quantum Physics · Physics 2019-02-12 V. N. Chernega , O. V. Man'ko , V. I. Man'ko

We address the statistics of continuous weak linear measurement on a few-state quantum system that is subject to a conditioned quantum evolution. For a conditioned evolution, both the initial and final states of the system are fixed: the…

Quantum Physics · Physics 2017-02-23 A. Franquet , Yuli V. Nazarov

In statistical physics, the challenging combinatorial enumeration of the configurations of a system subject to hard constraints (microcanonical ensemble) is mapped to a mathematically easier calculation where the constraints are softened…

Statistical Mechanics · Physics 2017-11-01 Tiziano Squartini , Diego Garlaschelli

In this work we determine a lower bound to the mean value of the quantum potential for an arbitrary state. Furthermore, we derive a generalized uncertainty relation that is stronger than the Robertson-Schr\"odinger inequality and hence also…

Quantum Physics · Physics 2020-05-08 F. Nicacio , F. T. Falciano

A generic non-integrable (unitary) out-of-equilibrium quantum process, when interrogated across many times, is shown to yield the same statistics as an (non-unitary) equilibrated process. In particular, using the tools of quantum stochastic…

Quantum Physics · Physics 2023-07-18 Neil Dowling , Pedro Figueroa-Romero , Felix A. Pollock , Philipp Strasberg , Kavan Modi

In this paper, inspired by the "Minimum Description Length Principle" in classical Statistics, we introduce a new method for predicting the outcomes of a quantum measurement and for estimating the state of a quantum system with minimum…

Quantum Physics · Physics 2020-12-25 Ahmad Shafiei Deh Abad , Mohammad Shahbazi

In its most basic form, the finite quantum de Finetti theorem states that the reduced k-partite density operator of an n-partite symmetric state can be approximated by a convex combination of k-fold product states. Variations of this result…

Quantum Physics · Physics 2009-01-12 Robert Koenig , Graeme Mitchison

One key issue of the foundation of statistical mechanics is the emergence of equilibrium ensembles in isolated and closed quantum systems. Recently, it was predicted that in the thermodynamic ($N\rightarrow\infty$) limit of large quantum…

Quantum Physics · Physics 2022-12-20 Mahdi Kourehpaz , Stefan Donsa , Fabian Lackner , Joachim Burgdörfer , Iva Březinová

The density operator of a quantum state can be represented as a complex joint probability of any two observables whose eigenstates have non-zero mutual overlap. Transformations to a new basis set are then expressed in terms of complex…

Quantum Physics · Physics 2012-04-26 Holger F. Hofmann

For studying the thermodynamic properties of systems using statistical mechanics we propose an ensemble that lies in between the familiar canonical and microcanonical ensembles. From a comparative study of these ensembles we conclude that…

Statistical Mechanics · Physics 2007-05-23 R. P. Venkataraman

We develop an approach where the quantum system states and quantum observables are described as in classical statistical mechanics -- the states are identified with probability distributions and observables, with random variables. An…

Quantum Physics · Physics 2019-04-23 Vladimir N. Chernega , Olga V. Man'ko , Vladimir I. Man'ko

The de Finetti representation theorem for continuous variable quantum system is first developed to approximate an N-partite continuous variable quantum state with a convex combination of independent and identical subsystems, which requires…

Quantum Physics · Physics 2016-09-28 Murphy Yuezhen Niu

In this article we derive a useful expectation identity using the language of quantum statistical mechanics, where density matrices represent the state of knowledge about the system. This identity allows to establish relations between…

Quantum Physics · Physics 2024-10-29 Boris Maulén , Sergio Davis , Daniel Pons

A new axiomatic characterization with a minimum of conditions for entropy as a function on the set of states in quantum mechanics is presented. Traditionally unspoken assumptions are unveiled and replaced by proven consequences of the…

Mathematical Physics · Physics 2014-07-02 Bernhard Baumgartner

We establish the ultimate quantum limits to the amplification of an unknown coherent state, both in the deterministic and probabilistic case, investigating the realistic scenario where the expected photon number is finite. In addition, we…

Quantum Physics · Physics 2013-05-28 Giulio Chiribella , Jinyu Xie

Based on the view that thermal equilibrium should be characterized through macroscopic observations, we develop a general theory about typicality of thermal equilibrium and the approach to thermal equilibrium in macroscopic quantum systems.…

Statistical Mechanics · Physics 2018-08-02 Hal Tasaki

Investigation on foundational aspects of quantum statistical mechanics recently entered a renaissance period due to novel intuitions from quantum information theory and to increasing attention on the dynamical aspects of single quantum…

Quantum Physics · Physics 2010-07-22 Barbara Fresch , Giorgio J. Moro

We consider an isolated, macroscopic quantum system. Let H be a micro-canonical "energy shell," i.e., a subspace of the system's Hilbert space spanned by the (finitely) many energy eigenstates with energies between E and E + delta E. The…

In a recent paper [J. Math. Phys. 47 082303 (2006)], Quantum Energy Inequalities were used to place simple geometrical bounds on the energy densities of quantum fields in Minkowskian spacetime regions. Here, we refine this analysis for…

Mathematical Physics · Physics 2008-11-26 Simon P. Eveson , Christopher J. Fewster