title: Quantum metrology with spin cat states under dissipation.
abstract: Quantum metrology aims to yield higher measurement precisions via quantum techniques such as entanglement. It is of great importance for both fundamental sciences and practical technologies, from testing equivalence principle to designing high-precision atomic clocks. However, due to environment effects, highly entangled states become fragile and the achieved precisions may even be worse than the standard quantum limit (SQL). Here we present a high-precision measurement scheme via spin cat states (a kind of non-Gaussian entangled states in superposition of two quasi-orthogonal spin coherent states) under dissipation. In comparison to maximally entangled states, spin cat states with modest entanglement are more robust against losses and their achievable precisions may still beat the SQL. Even if the detector is imperfect, the achieved precisions of the parity measurement are higher than the ones of the population measurement. Our scheme provides a realizable way to achieve high-precision measurements via dissipative quantum systems of Bose atoms.
authors.affiliation: School of Physics and Astronomy, Sun Yat-Sen University, Guangzhou 510275, China.|State Key Laboratory of Optoelectronic Materials and Technologies, Sun Yat-Sen University, Guangzhou 510275, China.
authors.forename: Jiahao
authors.initials: J
authors.lastname: Huang
authors.affiliation: School of Physics and Astronomy, Sun Yat-Sen University, Guangzhou 510275, China.|State Key Laboratory of Optoelectronic Materials and Technologies, Sun Yat-Sen University, Guangzhou 510275, China.
authors.forename: Xizhou
authors.initials: X
authors.lastname: Qin
authors.affiliation: School of Physics and Astronomy, Sun Yat-Sen University, Guangzhou 510275, China.|State Key Laboratory of Optoelectronic Materials and Technologies, Sun Yat-Sen University, Guangzhou 510275, China.
authors.forename: Honghua
authors.initials: H
authors.lastname: Zhong
authors.affiliation: School of Physics and Astronomy, Sun Yat-Sen University, Guangzhou 510275, China.|State Key Laboratory of Optoelectronic Materials and Technologies, Sun Yat-Sen University, Guangzhou 510275, China.
authors.forename: Yongguan
authors.initials: Y
authors.lastname: Ke
authors.affiliation: School of Physics and Astronomy, Sun Yat-Sen University, Guangzhou 510275, China.|State Key Laboratory of Optoelectronic Materials and Technologies, Sun Yat-Sen University, Guangzhou 510275, China.
authors.forename: Chaohong
authors.initials: C
authors.lastname: Lee