Orthogonal pairs and mutually unbiased bases

Abstract: The paper is devoted to representation theoretic and algebraic geometric aspects of the theory of orthogonal decompositions of Lie algebra sl(n) into Cartan subalgebras orthogonal with respect to Killing form and the relevant theory of mutually unbiased bases. We describe the main steps of our proof for the existence of 4-dimensional family of orthogonal pairs of Cartan subalgebras in sl(6). As an application, we prove existence of a real 4-dimensional family of pairs of mutually unbiased bases in C^6, thus solving the long standing problem in Quantum Information Theory.