  In a microscopic quantum system one cannot perform a simultaneous measurement
of particle and wave properties. This, however, may not be true for macroscopic
quantum systems. As a demonstration, we propose to measure the local
macroscopic current passed through two slits in a superconductor. According to
the theory based on the linearized Ginzburg-Landau equation for the macroscopic
pseudo wave function, the streamlines of the measured current should have the
same form as particle trajectories in the Bohmian interpretation of quantum
mechanics. By an explicit computation we find that the streamlines should show
a characteristic wiggling, which is a consequence of quantum interference.
