Hi everybody,

let O be a matrix with dimension n x n. I would like to write this
operator as a sum of kronecker products, i.e,

O= Sum_{i=1}^{i=k} lambda_i*kron(A_i,B_i)

with A_i and B_i operators of size (ma x ma) and (mb x mb), holding
that ma*mb=n. In particular I would like to obtain such a
decomposition that requires the minimum number of sums, that is, a
decomposition such that k is as low as possible. Does anybody know a
systematic way to obtain one possible set operators A_i and B_i and
the coefficients lambda_i for a given operator O?

Thanks,
Javi.

P.S: the kronecker product of two matrices is the usual tensorial
product of two matrices.