Effect of measurement probes upon the conductance of an interacting nanosystem: detection of an attached ring by nonlocal many body effects.

We consider a nanosystem connected to measurement probes via leads. When a magnetic flux is varied through a ring attached to one lead at a distance L(c) from the nanosystem, the effective nanosystem transmission |t(s)|(2) exhibits Aharonov-Bohm oscillations if the electrons interact inside the nanosystem. These oscillations can be very large if L(c) is small and if the nanosystem has almost degenerate levels which are put near the Fermi energy by a local gate.