Generalized limits for parameter sensitivity via quantum Ziv-Zakai bound

We study the generalized limit for parameter sensitivity in quantum estimation theory considering the effects of repeated and adaptive measurements. Based on the quantum Ziv-Zakai bound, we derive some lower bounds for parameter sensitivity when the Hamiltonian of a system is unbounded and when the adaptive measurements are implemented on the system. We also prove that the parameter sensitivity is bounded by the limit of the minimum detectable parameter. In particular, we examine several known states in quantum phase estimation with non-interacting photons and show that they cannot perform better than the Heisenberg limit in a much simpler way with our result. © 2012 IOP Publishing Ltd