On vector configurations that can be realized in the cone of positive matrices

Let $v_1$,..., $v_n$ be $n$ vectors in an inner product space. Can we find a natural number $d$ and positive (semidefinite) complex matrices $A_1$,..., $A_n$ of size $d imes d$ such that ${ m Tr}(A_kA_l)= $ for all $k,l=1,..., n$? For such matrices to exist, one must have $ geq 0$ for all $k,l=1,..., n$. We prove that if $n )$ has a positive factorization, then matrices $A_1$,..., $A_n$ as above exist. However, as we show by a large class of examples constructed with the help of the Clifford algebra, the converse implication is false.