Merges two density matrices into a single unified density matrix.

The resulting matrix's shape will be (t1.shape/2 + t2.shape/2) * 2. In other words, if t1 has shape [A,B,C,A,B,C] and t2 has shape [X,Y,Z,X,Y,Z], the resulting matrix will have shape [A,B,C,X,Y,Z,A,B,C,X,Y,Z].

t1 The first density matrix.
t2 The second density matrix.

A density matrix representing the unified state.