We knows that quantum information allows us to estimate certain unknown parameters to precisions beyond classical limits. The archetypal example, being the use of the NOON state - a superposition of N photons in either Mode A or Mode B - for phase estimation. Unfortunately, this same state is very fragile - if you accidentally lose a single one of these N photons, it becomes essentially useless.
Is this a generic trait for quantum metrology? This manuscript establishes such a trade-off. We related the performance of a probe state at estimating a parameter - as quantified by the quantum Fisher information-- to the amount of purity this parameter undergoes statistical fluctuation.
- Fragile states are better for quantum metrology
Kavan Modi, Lucas C. Céleri, Jayne Thompson, Mile Gu
