Conclusive precision bounds for SU(1,1) interferometers
Chenglong You, Sushovit Adhikari, Xiaoping Ma, Masahide Sasaki, Masahiro Takeoka, Jonathan P. Dowling · Physical Review A · 2019
In this paper, we revisit the quantum Fisher information (QFI) calculation in SU(1,1) interferometer considering different phase configurations. When one of the input modes is a vacuum state, we show by using phase averaging, different phase configurations give the same QFI. In addition, by casting the phase estimation as a two-parameter estimation problem, we show that the calculation of the quantum Fisher information matrix (QFIM) is necessary in general. Particularly, within this setup, the phase-averaging method is equivalent to a two-parameter estimation problem. We also calculate the phase sensitivity for different input states using QFIM approach.