Abstract
We study factorization and dilation properties of Markov maps between von Neumann algebras equipped with normal faithful states, i.e., completely positive unital maps which preserve the given states and also intertwine their automorphism groups. The starting point for our investigation has been the question of existence of non-factorizable Markov maps, as formulated by C. Anantharaman-Delaroche. We provide simple examples of non-factorizable Markov maps on \({M_n(\mathbb{C})}\) for all n ≥ 3, as well as an example of a one-parameter semigroup (T(t)) t≥0 of Markov maps on \({M_4(\mathbb{C})}\) such that T(t) fails to be factorizable for all small values of t > 0. As applications, we solve in the negative an open problem in quantum information theory concerning an asymptotic version of the quantum Birkhoff conjecture, as well as we sharpen the existing lower bound estimate for the best constant in the noncommutative little Grothendieck inequality.
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Communicated by M.B. Ruskai
Supported by the ERC Advanced Grant no. OAFPG 247321, and partially supported by the Danish Natural Science Research Council and the Danish National Research Foundation.
Partially supported by the National Science Foundation, DMS-0703869, and by the Danish Natural Science Research Council and the Danish National Research Foundation.
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Haagerup, U., Musat, M. Factorization and Dilation Problems for Completely Positive Maps on von Neumann Algebras. Commun. Math. Phys. 303, 555–594 (2011). https://doi.org/10.1007/s00220-011-1216-y
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DOI: https://doi.org/10.1007/s00220-011-1216-y