如何公式实现左下标？

<pre ><code >%\usepackage{amsmath} \[\sideset{_h}{_h}{\mathop{\langle\psi|Q_h|\psi\rangle}}\]</pre><p><img src="/data/ueditor/php/upload/image/20200422/1587555509942677.png" title="1587555509942677.png" alt="QQ截图20200422193819.png" style="max-width:650px"></p>

<p></p><p>使用tensor宏包中的\tensor命令</p><pre class="brush:plain;toolbar:false">$\tensor[_h]{\langle\psi&nbsp;|&nbsp;Q_h&nbsp;|&nbsp;\psi\rangle}{_h}$</pre><p><img src="/data/ueditor/php/upload/image/20200422/1587564531123573.png" title="1587564531123573.png" alt="Screenshot from 2020-04-22 22-08-07.png" style="max-width:650px"/></p><p>详细的使用见参考文档 texdoc tensor</p>