  We present the quantum and classical study of a four-well trapped
Bose-Einstein condensate (BEC) modeled by the Bose-Hubbard Hamiltonian. The
model used is fashioned as a minimal bipartite system consisting of a trimer
coupled weakly to a monomer. Semiclassical insights into the fragmentation
dynamics of the condensate is obtained by mapping out the Arnold web of the
high dimensional classical phase space. A remarkable one-to-one correspondence
between the quantum state space in occupation number representation and the
classical Arnold web in action space is observed. The relevance of dynamical
tunneling for the dynamics of Fock states near resonance junctions on the
Arnold web is highlighted. We also predict the possibility of manipulating the
transport within the trimer subsystem due to the weak coupling to the monomer.
