  In this work, the charge transfer fluctuation which was previously used for
$pp$ collisions is proposed for relativistic heavy-ion collisions as a QGP
probe. We propose the appearance of a local minimum at midrapidity for the
charge transfer fluctuation as a signal for a QGP. Within a two-component
neutral cluster model, we demonstrate that the charge transfer fluctuation can
detect the presence of a QGP as well as the size of the QGP in the rapidity
space. We also show that the forward-backward correlation of multiplicity can
be a similarly good measure of the presence of a QGP. Further, we show that the
previously proposed net charge fluctuation is sensitive to the existence of the
second phase only if the QGP phase occupies a large portion of the available
rapidity space.
