We present a top-down lower-bound method for depth-$4$ boolean circuits. In particular, we give a new proof of the well-known result that the parity function requires depth-$4$ circuits of size exponential in $n^{1/3}$. Our proof is an application of robust sunflowers and block unpredictability.

翻译：我们提出了一种针对深度四布尔电路的自顶向下下界方法。具体而言，我们给出了一个著名结论的新证明：奇偶函数需要规模为$n^{1/3}$指数级的深度四电路。我们的证明利用了稳健向日葵和不重复性概念。