  Phase transition in quantum many-body systems inevitably causes changes in
certain physical properties which then serve as potential indicators of
critical phenomena. Besides the traditional order parameters, characterization
of quantum entanglement has proven to be a computationally efficient and
successful method for detection of phase boundaries, especially in
one-dimensional models. Here we determine the rich phase diagram of the ground
states of a quantum spin-1/2 XXZ ladder by analyzing the variation of bipartite
and multipartite entanglements. Our study characterizes the different ground
state phases and notes the correspondence with known results, while
highlighting the finer details that emerge from the behavior of ground state
entanglement. Analysis of entanglement in the ground state provides a clearer
picture of the complex ground state phase diagram of the system using only a
moderate-size model.
