We construct the optimal strategy for the estimation of an unknown unitary transformation U∈SU(d). This includes, in addition to a convenient measurement on a probe system, finding which is the best initial state on which U is to act. When U∈SU(2), such an optimal strategy can be applied to simultaneously estimate both the direction and the strength of a magnetic field, and shows how to use a spin 1/2 particle to transmit information about a whole coordinate system instead of only a direction in space.
No takes yet. Share an insight, caveat, or question.
Acín et al. (2001) studied this question.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: