Qudit Entanglement
  We consider the separability of various joint states of D-dimensional quantum systems, which we call "qudits." We derive two main results: (i) the separability condition for a two-qudit state that is a mixture of the maximally mixed state and a maximally entangled state; (ii) lower and upper bounds on the size of the neighorhood of separable states surrounding the maximally mixed state for N qudits. 
P. Rungta (1), W. J. Munro (2), K. Nemoto (2), P. Deuar (2), G. J.   Milburn (2), C. M. Caves (1) ((1) University of New Mex...