  Phenomena of electromagnetically induced transparency (PEIT) may be
interpreted by the Autler-Townes Splitting (ATS), where the coupled states are
split by the coupling laser field, or by the quantum destructive interference
(QDI), where the atomic phases caused by the coupling laser and the probe laser
field cancel. We propose modulated experiments to explore the PEIT in an
alternative way by periodically modulating the coupling and the probe fields in
a ?-type three-level system. Our analytical and numerical results rule out the
ATS interpretation and show that the QDI interpretation is more appropriate for
the modulated experiments. The proposed experiments are readily implemented in
atomic gases, artificial atoms in superconducting quantum devices, or
three-level meta-atoms in meta-materials.

Quantum Physics