  Dark soliton (DS) and Josephson vortex (JV) in quasi-1D long Bose Josephson
junction (BJJ) can be interconverted by tuning Josephson coupling. Rates of the
interconversion as well as of the thermally activated phase-slip effect,
resulting in the JV switching its vorticity, have been evaluated. The role of
quantum phase-slip in creating superposition of JVs with opposite vorticities
as a qubit is discussed as well. Utilization of the JV for controlled and
coherent transfer of atomic Bose-Einstein condensate (BEC) is suggested.
