Wigner function and the probability representation of quantum states

The relation of the Wigner function with the fair probability distribution called tomographic distribution or quantum tomogram associated with the quantum state is reviewed. The connection of the tomographic picture of quantum mechanics with the integral Radon transform of the Wigner quasidistribution is discussed. The Wigner--Moyal equation for the Wigner function is presented in the form of kinetic equation for the tomographic probability distribution both in quantum mechanics and in the classical limit of the Liouville equation. The calculation of moments of physical observables in terms of integrals with the state tomographic probability distributions is constructed having a standard form of averaging in the probability theory. New uncertainty relations for the position and momentum are written in terms of optical tomograms suitable for direct experimental check. Some recent experiments on checking the uncertainty relations including the entropic uncertainty relations are discussed.Comment: 4 p, contribution to the Proceedings of the conference "Wigner 111 - Colourful and Deep (November 11-13 Budapest, Hungary

Tomographic entropic inequalities in the probability representation of quantum mechanics

A review of the tomographic-probability representation of classical and quantum states is presented. The tomographic entropies and entropic uncertainty relations are discussed in connection with ambiguities in the interpretation of the state tomograms which are considered either as a set of the probability distributions of random variables depending on extra parameters or as a single joint probability distribution of these random variables and random parameters with specific properties of the marginals. Examples of optical tomograms of photon states, symplectic tomograms, and unitary spin tomograms of qudits are given. A new universal integral inequality for generic wave function is obtained on the base of tomographic entropic uncertainty relations.Comment: 9 pages; to be published in AIP Conference Proceedings as a contribution to the conference "Beauty in Physics: Theory and Experiment" (the Hacienda Cocoyoc, Morelos, Mexico, May 14--18, 2012

Correlations in a system of classical--like coins simulating spin-1/2 states in the probability representation of quantum mechanics

An analog of classical "hidden variables" for qubit states is presented. The states of qubit (two-level atom, spin-1/2 particle) are mapped onto the states of three classical--like coins. The bijective map of the states corresponds to the presence of correlations of random classical--like variables associated with the coin positions "up" or "down" and the observables are mapped onto quantum observables described by Hermitian matrices. The connection of the classical--coin statistics with the statistical properties of qubits is found

Conventional Quantum Mechanics Without Wave Function and Density Matrix

The tomographic invertable map of the Wigner function onto the positive probability distribution function is studied. Alternatives to the Schr\"odinger evolution equation and to the energy level equation written for the positive probability distribution are discussed. Instead of the transition probability amplitude (Feynman path integral) a transition probability is introduced. A new formulation of the conventional quantum mechanics (without wave function and density matrix) based on the ``probability representation'' of quantum states is given. An equation for the propagator in the new formulation of quantum mechanics is derived. Some paradoxes of quantum mechanics are reconsidered.Comment: Latex, 37 pages, to be published as lectures given at the Latin American School of Physics, (XXXI ELAF, July-August, 1998, Mexico) in Casta\~nos, O., Hacyan, S., Lopez-Pe\~na, R., (Eds.), AIP Conference Proceedings (American Institute of Physics, New York, 1999