Figure 1

Generation of the superposition spin state. (a) Atomic levels and interaction with light. Both ground and excited states are spin $1/2$ states. The top diagram shows the initial coherent spin state in $z$ representation. The middle diagram shows the same state in $x$ representation along with the virtual transitions used for the generation of the spin squeezed state. The bottom diagram shows the spin squeezed state in $z$ representation along with the interaction used for the cat state generation. (b) The spin squeezed state generated by a QND measurement using the first pulse of light is represented by the “banana” shape. The following QND measurement of the number operator ${\widehat{n}}_A$ corresponds to intersecting the banana with a plane of a finite width. Thus the final state has two components lying at positive and negative values of $J_y$, i.e., it is a superposition state.Reuse & Permissions

Figure 2

The solid line shows the amplitude of the state ${\psi }_A(p_R)$, Eq. (5), in the $p_A$ basis for parameters ${\xi }^2=20$, $p_R/\beta =7$, and $\beta =1/3$. The dotted line shows the approximation Eq. (8) for the same values of the parameters.Reuse & Permissions