I have a minimizing problem.

$$\min y$$
$$xQx'\leq y$$
$$0\leq x_i\leq1$$
$$Az\leq b$$
where $Q$ is diagonal and has positive diagonal values and $A\in\mathbb R^{m\times n}$ and $b\in\mathbb R^m$ are constant matrix and vector respectively while $z\in\mathbb R^n$ is variables that contain $x_1,\dots,x_t,y\in\mathbb R$ as well.

>Is this problem $NP$-hard or solvable in polynomial time?