On Two Ways to Look for Mutually Unbiased Bases

Two equivalent ways of looking for mutually unbiased bases are discussed in this note. The passage from the search for d+1 mutually unbiased bases in C(d) to the search for d(d+1) vectors in C(d*d) satisfying constraint relations is clarified. Symmetric informationally complete positive-operator-valued measures are briefly discussed in a similar vein.Comment: three pages to be published in Acta Polytechnica (Czech Technical University in Prague

ON TWO WAYS TO LOOK FOR MUTUALLY UNBIASED BASES

Two equivalent ways of looking for mutually unbiased bases are discussed in this note. The passage from the search for d+1 mutually unbiased bases in Cd to the search for d(d+1) vectors in Cd2 satisfying constraint relations is clarified. Symmetric informationally complete positive-operator-valued measures are briefly discussed in a similar vein

Equiangular Vectors Approach to Mutually Unbiased Bases

Two orthonormal bases in the d-dimensional Hilbert space are said to be unbiased if the square modulus of the inner product of any vector of one basis with any vector of the other equals 1 d. The presence of a modulus in the problem of finding a set of mutually unbiased bases constitutes a source of complications from the numerical point of view. Therefore, we may ask the question: Is it possible to get rid of the modulus? After a short review of various constructions of mutually unbiased bases in Cd, we show how to transform the problem of finding d + 1 mutually unbiased bases in the d-dimensional space Cd (with a modulus for the inner product) into the one of finding d(d+1) vectors in the d2-dimensional space Cd2 (without a modulus for the inner product). The transformation from Cd to Cd2 corresponds to the passage from equiangular lines to equiangular vectors. The transformation formulas are discussed in the case where d is a prime number

Repercusiones cuánticas de los estados clásicamente correlacionados : Aspectos informacionales y computacionales

La Información Cuántica, como disciplina que hereda virtudes y defectos de la Teoría de la Información y de la Mecánica Cuántica, ha brindado, durante los últimos años, un avance considerable en el entendimiento y resolución de ciertos problemas de Fundamentos de la Cuántica. El formalismo, sin embargo, no está exento de interrogantes propios que son intensamente estudiados. Algunas de las contribuciones más importantes se vinculan con las potencialidades de los sistemas mecánico-cuánticos como recursos computacionales más poderosos que los implementables mediante sistemas que no evidencian efectos cuánticos. La clave, en esos casos, está en el tipo de correlaciones que pueden establecerse entre dos o más partes de los sistemas. En este trabajo, presento varios resultados en los que estudio aspectos informacionales de los sistemas cuánticos, presentes incluso en los estados denominados clásicamente correlacionados.Quantum Information, as a discipline that inherits the strengths and weaknesses of Information Theory and Quantum Mechanics, has provided, in recent years, considerable progress in understanding and solving certain problems on the Foundations of Quantum Mechanics. The formalism, however, has its own open questions that are intensely studied nowadays. Some of the most important contributions are realated to the potentiality of quantum-mechanical systems as more powerful computational resources than those implementable by means of systems that do not show quantal effects. The key, in those cases, is on the class of correlations that can be established between two or more parts of the systems. In this work, I present several results that explore informational aspects of quantum systems, which show up even in the so-called classically-correlated states.Facultad de Ciencias Exacta