I am still quite new to cvx. Here is the semidefinite program I want to implement.

I am curious how to implement the matrix (AX), as a first step of the optimization objective function.

A is some 4-dimensional numerical tensor, where X is the the PSD relaxation of the gram matrix x^T x, so X is the variable. (AX)_{kl} is an element in the matrix (AX), and (AX)_{kl} = tr(A_{kl} X). A_{kl} is a slice of A, and a matrix.

In other words, (AX) is a matrix of traces in the form (A X)_{kl} = tr(A_{kl} X).