In quantum mechanics, macroscopic quantum self-trapping is when two Bose–Einstein condensates weakly linked by an energy barrier which particles can tunnel through, nevertheless end up with a higher average number of bosons on one side of the junction than the other. The junction of two Bose–Einstein condensates is mostly analogous to a Josephson junction, which is made of two superconductors linked by a non-conducting barrier. However, superconducting Josephson junctions do not display macroscopic quantum self-trapping, and thus macroscopic quantum self-tunneling is a distinguishing feature of Bose–Einstein condensate junctions. Self-trapping occurs when the self-interaction energy Λ Λ between the Bosons is larger than a critical value called Λ Λ c MJJ . Λ Λ c MJJ = 1 + 1 − − z ( 0 ) 2 cos ⁡ ⁡ ( θ θ ( 0 ) + θ θ A-C ) z ( 0 ) 2 / 2