  Quantum triangles can work as interferometers. Depending on their geometric
size and interactions between paths, "beats" {\it and/or} "steps" patterns are
observed. We show that when inter-level distances between level positions in
quantum triangles periodically change with time, formation of beats {\it
and/or} steps no longer depends only on the geometric size of the triangles but
also on the characteristic frequency of the transverse signal. For large-size
triangles, we observe the coexistence of beats {\it and} steps when the
frequency of the signal matches that of non-adiabatic oscillations and for
large frequencies, a maximum of four steps instead of two as in the case with
constant interactions is observed. Small-size triangles also revealed
counter-intuitive interesting dynamics for large frequencies of the field:
unexpected two-step patterns are observed. When the frequency is large and
tuned such that it matches the uniaxial anisotropy, three-step patterns are
observed. We have equally observed that when the transverse signal possesses a
static part, steps maximize to six. These effects are semi-classically
explained in terms of Fresnel integrals and quantum mechanically in terms of
quantized fields with a photon-induced tunneling process. Our expressions for
populations are in excellent agreement with the gross temporal profiles of
exact numerical solutions. We compare the semi-classical and quantum dynamics
in the triangle and establish the conditions for their equivalence.
