where 𝐌(𝐚 % ()& ) denotes a conversion from DPEM layer to DPEM (i.e., from the unique elements of the DPEM stored as a vector to the full matrix form), and diag[𝐌(𝐚 % ()& )] denotes the diagonalization of the DPEM and saving the eigenvalues into vector 𝐚 % ( .