6 research outputs found
Optimal estimation of high-dimensional unitary transformations
We propose an estimation procedure for -dimensional unitary
transformations. For , the unitary transformations close to the identity
are estimated saturating the quantum Cram\'er-Rao bound. For , the
estimation of all unitary transformations is also optimal with some prior
information. We show through numerical simulations that, even in the absence of
prior information, two-dimensional unitary transformations can be estimated
with greater precision than by means of standard quantum process tomography.Comment: 8+14 pages, 6 figure