  In this paper we examine Interaction-free measurement (IFM) where both the
probe and the object are quantum particles. We argue that in this case the
description of the measurement procedure must by symmetrical with respect to
interchange of the roles of probe and object. A thought experiment is being
suggested that helps to determine what does and what doesn't happen to the
state of the particles in such a setup. It seems that unlike the case of
classical object, here the state of both the probe and the object must change.
A possible explanation of this might be that the probe and the object form an
entangled pair as a result of non-interaction.
