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Additivity questions in quantum information theory

Mathematical Physics & Probability

Speaker: Christopher King, Northeastern University
Location: 2112 MSB
Start time: Thu, Apr 6 2006, 3:10PM

Attempts to extend Shannon's noisy coding theorem to a quantum setting have led to interesting mathematical questions concerning products of completely positive maps on matrix algebras. Specifically for trace-preserving maps it is conjectured that the output state with minimal entropy is always a product state -- this is equivalent to the statement that minimal output entropy is additive for such maps. I will review the background to this problem, and describe its relation to some inequalities that arose in different contexts, including strong subadditivity and Hanner's inequality. I will then show how some new matrix inequalities can be used to prove special cases of this result.