% MathType!MTEF!2!1!+- % feaahqart1ev3aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbWexLMBbXgBd9gzLbvyNv2CaeHbl7mZLdGeaGqiVu0Je9sqqr % pepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9vqaqpepm0xbba9pwe9Q8fs % 0-yqaqpepae9pg0FirpepeKkFr0xfr-xfr-xb9adbaqaaeWaciGaai % aabeqaamaabaabauaakeaacaGG8bacbiGaa8hAamaaBaaaleaacaqG % ZbGaaeiCaaqabaGccaqG3bWaaSbaaSqaaiaaikdaaeqaaOGaaiiFam % aaCaaaleqabaGaaGOmaaaaaaa!4707! \[|{h_{{\rm{sp}}}}{{\rm{w}}_2}{|^2}\]转换成迹的形式

将 ${h_{\rm{sp}}}{{\rm{w}}_2}$ 展开得到：

$$
\begin{aligned}
|h_{\rm{sp}}w_2|^2 &= (h_{\rm{sp}}w_2)(h_{\rm{sp}}w_2)^*\\
&=(h_{\rm{sp}}w_2)(w_2^*h_{\rm{sp}}^*)\\
&= h_{\rm{sp}}w_2w_2^*h_{\rm{sp}}^*\\
&=\operatorname{Tr}(h_{\rm{sp}}w_2w_2^*h_{\rm{sp}}^*)
\end{aligned}
$$

因此，$|{h_{{\rm{sp}}}}{{\rm{w}}_2}{|^2}$ 可以转换成 $\operatorname{Tr}(h_{\rm{sp}}w_2w_2^*h_{\rm{sp}}^*)$ 的形式。