We study the entanglement features of the ground state of a system composed of spin 1 and 1/2 parts. In the light of the ground state degeneracy, the notion of average entanglement is used to measure the entanglement of the Hilbert subspace. The entanglement properties of both a general superposition as well as the mixture of the degenerate ground states are discussed by means of average entanglement and the negativity respectively.
Financed by the National Centre for Research and Development under grant No. SP/I/1/77065/10 by the strategic scientific research and experimental development program:
SYNAT - “Interdisciplinary System for Interactive Scientific and Scientific-Technical Information”.