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：我们提出了一种深度为$4$的布尔电路自顶向下下界的方法。特别是，我们提供了一个新的证明，证明了奇偶函数需要尺寸为$n^{1/3}$指数级的深度为$4$电路。我们的证明是应用了“韧性向日葵”和“块不可预测性”的结果。