  Transverse field Ising model is a common model in quantum magnetism and is
often illustrated as an example for quantum phase transition. Its physical
origin in quantum magnets, however, is actually not quite well-understood. The
quantum mechanical properties of this model on frustrated systems are not
well-understood either. We here clarify the physical origin, both extrinsic one
and intrinsic one, for the transverse field of the quantum Ising model, and
then explain the quantum effects in the Kagome system. We discuss the quantum
plaquette order and the quantum phase transition out of this ordered state in
the rare-earth Kagome magnets. Our specific results can find their relevance in
the rare-earth tripod Kagome magnets.
