Factorization and dilation problems for completely positive maps on von Neumann algebras

TY - JOUR

T1 - Factorization and dilation problems for completely positive maps on von Neumann algebras

AU - Haagerup, Uffe

AU - Musat, Magdalena

PY - 2011/4

Y1 - 2011/4

N2 - 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 Mn(ℂ) for all n ≥ 3, as well as an example of a one-parameter semigroup (T(t))t≥0 of Markov maps on M4(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.

AB - 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 Mn(ℂ) for all n ≥ 3, as well as an example of a one-parameter semigroup (T(t))t≥0 of Markov maps on M4(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.

U2 - 10.1007/s00220-011-1216-y

DO - 10.1007/s00220-011-1216-y

M3 - Journal article

SN - 0010-3616

VL - 303

SP - 555

EP - 594

JO - Communications in Mathematical Physics

JF - Communications in Mathematical Physics

ER -