Josephson vortex between two atomic Bose-Einstein condensates

The Josephson vortex (JV) between two long parallel coupled atomic Bose-Einstein condensates (BECs) is considered analytically and numerically in the quasi-one-dimensional limit. Its closed analytical solution is presented. It is found that, upon increasing the Josephson coupling, the JV transforms spontaneously into a dark soliton and vice versa. We suggest how the JV and its transformation can be detected. We also propose that the JV can be utilized for controlled and coherent transfer of atomic BECs and as a possible mobile qubit.