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We introduce two methods for estimating the density matrix for a quantum system: Quantum Maximum Likelihood and Quantum Variational Inference. In these methods, we construct a variational family to model the density matrix of a mixed…

Quantum Physics · Physics 2019-04-15 Kyle Cranmer , Siavash Golkar , Duccio Pappadopulo

Conditional distributions, as defined by the Markov category framework, are studied in the setting of matrix algebras (quantum systems). Their construction as linear unital maps are obtained via a categorical Bayesian inversion procedure.…

Quantum Physics · Physics 2021-09-14 Arthur J. Parzygnat

We show that the density-matrix states of noncomposite qudit systems satisfy entropic and information relations like the subadditivity condition, strong subadditivity condition, and Araki--Lieb inequality, which characterize hidden quantum…

Quantum Physics · Physics 2016-05-04 Margarita A Man'ko , Vladimir I Man'ko

A method of representing probabilistic aspects of quantum systems is introduced by means of a density function on the space of pure quantum states. In particular, a maximum entropy argument allows us to obtain a natural density function…

Quantum Physics · Physics 2015-06-26 D. C. Brody , L. P. Hughston

Counterfactual definiteness (CFD) means that if some property is measured in some context, then the outcome of the measurement would have been the same had this property been measured in a different context. A context includes all other…

Quantum Physics · Physics 2023-09-22 Janne V. Kujala , Ehtibar N. Dzhafarov

A random matrix theory approach is applied in order to analyze the localization properties of local spectral density for a generic system of coupled quantum states with strong static imperfection in the unperturbed energy levels. The system…

Quantum Physics · Physics 2009-11-07 V. S. Starovoitov

A statistical description of part of a many body system often requires a non-Hermitian random matrix ensemble with nature and strength of randomness sensitive to underlying system conditions. For the ensemble to be a good description of the…

Disordered Systems and Neural Networks · Physics 2024-12-17 Mohd. Gayas Ansari , Pragya Shukla

The standard assumption for the equilibrium microcanonical state in quantum mechanics, that the system must be in one of the energy eigenstates, is weakened so as to allow superpositions of states. The weakened form of the microcanonical…

Quantum Physics · Physics 2007-05-23 Dorje C Brody , Daniel W Hook , Lane P Hughston

In recent years, non-Hermitian quantum systems (NHQS) have been actively studied. In conventional quantum mechanics, Hermiticity is a fundamental property of Hamiltonians. In NHQS, however, states evolve under non-Hermitian Hamiltonians and…

Quantum Physics · Physics 2025-12-23 Hiroto Oka

If the block universe view is correct, the future and the past have similar status and one would expect physical theories to involve final as well as initial boundary conditions. A plausible consistency condition between the initial and…

Quantum Physics · Physics 2007-05-23 D. J. Miller

A density matrix $\rho$ may be represented in many different ways as a mixture of pure states, $\rho = \sum_i p_i |\psi_i\ra \la \psi_i|$. This paper characterizes the class of probability distributions $(p_i)$ that may appear in such a…

Quantum Physics · Physics 2009-10-31 M. A. Nielsen

Based on the form invariance of the structures given by Khinchin's axiomatic foundations of information theory and the pseudoadditivity of the Tsallis entropy indexed by q, the concept of conditional entropy is generalized to the case of…

Quantum Physics · Physics 2009-11-06 Sumiyoshi Abe , A. K. Rajagopal

We use open quantum system techniques to construct one-parameter semigroups of positive maps and apply them to study the entanglement properties of a class of 16-dimensional density matrices, representing states of a 4x4 bipartite system.

Quantum Physics · Physics 2007-05-23 Fabio Benatti , Roberto Floreanini , Marco Piani

A central question in quantum computation is to identify the resources that are responsible for quantum speed-up. Quantum contextuality has been recently shown to be a resource for quantum computation with magic states for odd-prime…

Quantum Physics · Physics 2017-09-26 Juan Bermejo-Vega , Nicolas Delfosse , Dan E. Browne , Cihan Okay , Robert Raussendorf

One of the interesting topics in quantum contextuality is the construction for various non-contextual inequalities. By introducing a new structure called hyper-graph, we present a general method, which seems to be analytic and extensible,…

Quantum Physics · Physics 2017-09-29 Weidong Tang , Sixia Yu

We quantitatively analyze the dynamics of the quantum phase distribution associated with the reduced density matrix of a system, as the system evolves under the influence of its environment with an energy-preserving quantum nondemolition…

Quantum Physics · Physics 2009-11-13 Subhashish Banerjee , Joyee Ghosh , R. Ghosh

The underlying probabilistic theory for quantum mechanics is non-Kolmogorovian. The order in which physical observables will be important if they are incompatible (non-commuting). In particular, the notion of conditioning needs to be…

Quantum Physics · Physics 2019-07-30 John E. Gough

In noninteracting limit, the density of states of a many body system can be expressed as the convolution of single body density of states of its subunits. Here we use the formulation to derive the ensemble averaged many body density of…

Statistical Mechanics · Physics 2022-05-25 Pragya Shukla

An algebraic procedure to find extremal density matrices for any Hamiltonian of a qudit system is established. The extremal density matrices for pure states provide a complete description of the system, that is, the energy spectra of the…

Mathematical Physics · Physics 2016-10-03 Armando Figueroa , Julio A. López-Saldívar , Octavio Castaños , Ramón López-Peña

Systems of identical particles possessing non-local interactions are capable of exhibiting extra-classical properties beyond the characteristic quantum length scales. This letter derives the dynamics of such systems in the non-relativistic…

Cosmology and Nongalactic Astrophysics · Physics 2020-03-24 Erik W Lentz , Thomas R Quinn , Leslie J Rosenberg