Entanglement of Formation for Qubit-Qudit System Using Partition of Qudit System into a Set of Qubit System

Gerjuoy (Phys. Rev. A 67:052308, 2003) has derived a closed-form lower bound for the entanglement of formation of a mixed qubit-qudit system (qudit system has d levels with d≥3). In this paper, inspired by Gerjuoy’s method, we propose a scheme that partitions a qubit-qudit system into d(d?1)/2 qubit-qubit systems, which can be treated by all known methods pertinent to qubit-qubit system. The method is demonstrated by a qubit-qudit system (the levels of qudit are d=3 and d=5, respectively).