  We study a system of three coherently coupled states, where one state is
shifted periodically against the other two. We discover such a system possesses
a dark Floquet state at zero quasienergy and always with negligible population
at the intermediate state. This dark Floquet state manifests itself dynamically
in terms of the suppression of inter-state tunneling, a phenomenon known as
coherent destruction of tunneling. We suggest to call it dark coherent
destruction of tunneling (DCDT). At high frequency limit for the periodic
driving, this Floquet state reduces to the well-known dark state widely used
for STIRAP. Our results can be generalized to systems with more states and can
be verified with easily implemented experiments within current technologies.
