  Quantified CTL (QCTL) extends the temporal logic CTL with quantifications
over atomic propositions. This extension is known to be very expressive: QCTL
allows us to express complex properties over Kripke structures (it is as
expressive as MSO). Several semantics exist for the quantifications: here, we
work with the structure semantics, where the extra propositions label the
Kripke structure (and not its execution tree), and the model-checking problem
is known to be PSPACE-complete in this framework. We propose a new
model-checking algorithm for QCTL based on a reduction to QBF. We consider
several reduction strategies and we compare them with a prototype (based on
several QBF solvers) on different examples.
