The condensate in a superconducting system involves a deformation of the field that creates the condensed fermion pairs. Thus, the process of addition or removal of a correlated Cooper pair of electrons from a superconductor, as in the Josephson effect, or of a nucleon pair from a superfluid nucleus, constitutes a rotational mode in gauge space in which particle number plays the role of angular momentum. While the Josephson junction trasiently established between two superfluid nuclei in a heavy in collision --through which pair tunneling proceeds mainly in terms of successive transfer of entangled nucleons -- is deprived from the macroscopic aspects of a supercurrent, one can study the process in terms of individual quantum states. Something not possible within the framework of low temperature condensed matter physics. And, by the same token , accurately determine the nuclear Cooper pair mean square radius (correlation length). Again, a remarkable outcome of the study of nuclear pair tunneling between superfluid nuclei. The observations lying at the basis of the above breakthroughs in the study of nuclear superfluidity will be discussed.