Jiangxi Institute of Education

We consider single-particle coherence and spin squeezing in Bose-Einstein Condensate (BEC) with Josephson-like coupling when the BEC is initially in a coherent spin state.Josephson-like coupling gives vanishing contribution to single-particle coherence and spin squeezing.The stronger squeezing can be achieved by increasing the number of atoms.

We consider how to generate spin squeezed state of atom-photon with stimulated Raman transition.We first derive the effective Hamiltonian and then obtain the anal. solution for state vector, the optimally squeezed angle and then the squeezing parameter.It is shown that the spin squeezed state can be generated by appropriately adjusting the atom-laser dipole interaction and two-photon detuning.

We investigate phase estimation sensitivity two-species Bose-Einstein condensate with nonlinear interat. interactions and Josephson-like tunneling.Numerical analyzes of quantum Fisher information and phase estimation sensitivity are presented.Quantum Fisher information and phase estimation sensitivity are independent of Josephson-like coupling and they are insensitive to interat. interaction.The better values of quantum Fisher information and phase estimation sensitivity can be achieved by increasing the population difference of atoms in two condensates.