  We investigate the interaction potential of superconducting vortices at the
full quantum level. We formulate the interaction potential in a constrained
path integral and calculate it by the quantum Monte Carlo simulation. The
vortex-vortex potential is attractive (type-I), repulsive (type-II), and flat
(critical) depending on a coupling constant. The vortex-antivortex potential
also depends on the coupling constant at long range but is always attractive at
short range.
