Help!DCP error: Invalid quadratic form(s): not a square

The error message is because you are multiplying t and Q, which is non-convex, hence not allowed by CVX.

If that were permissible, I would have suggested that when you first asked how to formulate this problem in CVX at CVX programming error: Cannot perform the operation: {convex} ./ {convex} - #2 by Mark_L_Stone .