Is the large uncertainty of δCP fundamentally encoded in the neutrino quantum state?

Quantum estimation theory provides a framework to quantify the ultimate precision limits for parameter estimation in physical systems. I will introduce its basic concepts and apply them to neutrino oscillations, focusing on the estimation of the PMNS parameters.

A central puzzle is why the CP, violating phase δCP remains significantly less constrained than the other mixing parameters. Using quantum estimation tools, I will  show that this limitation is not due to a lack of information encoded in the neutrino quantum state. Instead, it arises from the suboptimal nature of standard flavor measurements, particularly near the first oscillation peak.

I will discuss how optimized measurement strategies can improve sensitivity to δCP, and compare the achievable precision with that of other mixing parameters, for which current measurements are already close to optimal.