Split spin-squeezed Bose-Einstein Condensates

We investigate and model the behaviour of split spin-squeezed Bose-Einstein condensates (BECs) system. In such a system, a spin-polarized BEC is first squeezed using a $(S^z)^2$ interaction, then are split into two separate clouds. After the split, we consider that the particle number in each cloud collapses to a fixed number. We show that this procedure is equivalent to applying an interaction corresponding to squeezing each cloud individually plus an entangling operation. We analyse the system's entanglement properties and show that it can be detected using correlation-based entanglement criteria. The nature of the states are illustrated by Wigner functions and have the form of a correlated squeezed state. The conditional Wigner function shows high degrees of non-classicality for dimensionless squeezing times beyond $1/\sqrt{N}$, where $N$ is the number of particles per BEC.