  We study the dephasing-assisted precision of parameter estimation (PPE)
enhancement in atom interferometer under dynamical decoupling (DD) pulses.
Through calculating spin squeezing (SS) and quantum Fisher information (QFI),
we find that dephasing noise can improve PPE by inducing SS, and the DD pulses
can maximize the improvement. It is indicated that in the presence of DD
pulses, the dephasing-induced SS can reach the limit of \textquotedblleft
one-axis twisting\textquotedblright\ model, $\xi^2\simeq N^{-2/3}$ with $\xi^2$
being the SS parameter and N the number of atoms. In particular, we find that
the DD pulses can amplify the dephasing-induced QFI by a factor of $\simeq N/2$
compared with the noise-free case, which means that under the control of DD
pulses, the dephasing noise can enhance the PPE to the scale of $\sqrt{2}/N$,
the same order of magnitude of Heisenberg limit (1/N).

Quantum Physics