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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 DSVs 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 $phi -theta /2$ $in left[ kpi/2,3kpi /4right) left( kin mathbb{Z}right)$, we can obtain the accuracy of parameter estimation approaching the ultimate quantum limit through using the DSV state with the larger displacement and squeezing strength, whereas $phi -theta /2$ $in left(3kpi /4,kpi right] left( kin mathbb{Z}right) $, the optimal estimation accuracy can be acquired only when the DSV state degenerates to a squeezed-vacuum state.
Photon-number correlation measurements are performed on bright squeezed vacuum states using a standard Bell-test setup, and quantum correlations are observed for conjugate polarization-frequency modes. We further test the entanglement witnesses for t
We study the sensitivity and resolution of phase measurement in a Mach-Zehnder interferometer with two-mode squeezed vacuum (<n> photons on average). We show that super-resolution and sub-Heisenberg sensitivity is obtained with parity detection. In p
We show that a nonlinear asymmetric directional coupler composed of a linear waveguide and a nonlinear waveguide operating by nondegenerate parametric amplification is an effective source of single-mode squeezed light. This is has been demonstrated,
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