The quantum Fisher information (QFI) sets a fundamental limit on how precisely we can measure physical quantities. It plays a role in everything from gravitational wave detection to emerging technologies like quantum lidar. A natural question is: can we always design measurements that actually reach this limit? For single parameters, yes — but for multiple parameters, the story is much trickier. In fact, finding general conditions for when the QFI bound is achievable remains an open problem. In this talk I’ll give an overview of the issue and walk through three simple examples that show why this seemingly straightforward question hides surprising complexity.

(https://www.sciencedirect.com/science/article/pii/S0375960125002257)

Pizza and drinks will be served after the seminar in ATL 2117.