hi guys. i have a real problem to plot or obtain quantum negativity of a bosonic system. please people who know quantum information help me. the Hamiltonian of the system is 
negativity defined as the absolute sum of the negative eigenvalues of partial transpose of density matrix. i wrote a code in Mathematica to plot quantum negativity versus r and alpha but it gives nothing. here is the code i used. ( the program is attached to the post) 
in above code the first matrix is the density matrix of the system. the second matrix is the partial transpose of the density matrix and line 4 is negativity. the plot should be look like this. 
please help me to plot it. it is necessary. thank you.
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