Phase-sensitive nonclassical properties in quantum metrology with a displaced squeezed vacuum state

We predict that the phase-dependent error distribution of locally unentangled quantum states directly affects quantum parameter estimation accuracy. Therefore, we employ the displaced squeezed vacuum (DSV) state as a probe state and investigate an interesting question of the phase-sensitive nonclassical properties in the DSV's metrology. We found that the accuracy limit of parameter estimation is a function of the phase-sensitive parameter phi - theta/2 with a period pi. We show that when phi - theta/2 is an element of [k pi/2, 3k pi/4) (k is an element of Z), we can obtain the accuracy of parameter estimation approaching the ultimate quantum limit through the use of the DSV state with the larger displacement and squeezing strength, whereas when phi - theta/2 is an element of (3k pi/4, k pi] (k is an element of Z), the optimal estimation accuracy can be acquired only when the DSV state degenerates to a squeezed vacuum state. (C) 2021 Optical Society of America