双模压缩Fock态在量子相位估计中的应用

Applications of Two-Mode Squeezed Fock State in Quantum Phase Estimation

量子精密测量主要是利用量子态的非经典效应来提高待测参数估计的精度.本文研究了双模压缩Fock态作为马赫-曾德尔干涉仪的探测态时,增加双模Fock态的粒子数,可以有效改善基于量子Fisher信息的量子Cramér-Rao界限,这一相位测量精度的最终极限.对于对称的双模压缩Fock态,宇称测量所得到的相位测量精度可以达到量子Cramér-Rao界限.而对于非对称的双模压缩Fock态,宇称测量却不能.因此,宇称测量并不总是一种最优测量方案.

Quantum precision is mainly to estimate accurately the value of an unknown parameter with the help of the quantum effects.When the two-mode squeezed Fock state considered as an interferometer state of a Mach-Zehnder interferometer,compared with the two-mode squeezed vacuum state,two-mode squeezed Fock state can further improve the quantum Cramér-Rao bound via the quantum Fisher information.On the other hand,via the parity detection,our results show that,for the symmetric two-mode squeezed Fock state,the phase sensitivity obtained by the parity detection can reach the quantum Cramér-Rao bound.While for the asymmetric two-mode squeezed Fock state,it is not valid.Therefore,our results show again that the parity detection is not always the optimal detection for some nonclassical quantum states.