no code implementations • 15 Apr 2016 • Dong Xia, Vladimir Koltchinskii
Let ${\mathcal S}_m$ be the set of all $m\times m$ density matrices (Hermitian positively semi-definite matrices of unit trace).
no code implementations • 17 Jul 2015 • Vladimir Koltchinskii, Dong Xia
The density matrices are positively semi-definite Hermitian matrices of unit trace that describe the state of a quantum system.
no code implementations • 29 Nov 2010 • Vladimir Koltchinskii, Alexandre B. Tsybakov, Karim Lounici
We show that the obtained rates are optimal up to logarithmic factors in a minimax sense and also derive, for any fixed matrix $A_0$, a non-minimax lower bound on the rate of convergence of our estimator, which coincides with the upper bound up to a constant factor.