Haixing Hu
We must know, we shall know

In the chapter 1.2 of Michael Nielsen’s book Quantum Comutation and Quantum Information, it is said that the state of a qubit could be rewritten as \begin{equation}\label{eq_bloch} |\psi\rangle = \cos\frac{\theta}{2}|0\rangle + e^{i\varphi}\sin\frac{\theta}{2}|1\rangle, \end{equation} but the inference procedure was not given. Here we try to infer it.

载于《上海文化》2012年第5期

一、左边的办公室

冯•诺伊曼教授每年换一部新凯迪拉克。早上十点，他把爱车停在帕尔玛物理实验室门口， 神采奕奕地走进隔壁数学系的办公室。那时候普林斯顿高等研究院才刚成立，和数学系挤在 一幢叫作Fine Hall的楼—— “还不错的楼”。冯•诺伊曼教授总是穿一身笔挺的西装，以免别 人把他错当成学生。他太年轻，三十出头，却已经到达了学术顶峰，和五十多岁的物理学家 爱因斯坦、数学家维布伦（Oswald Veblen）、数学家亚历山大（James Alexander）一起成 了高等研究院最初任命的四位教授。

Use the following code snip

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Mac OS X Spotlight search is a powerful beast, returning all types of search results in seconds. However, if you don’t use it to launch apps, or find files then it can take up precious CPU cycles for no good reason.

Use the following commands to add user to a group:

sudo dseditgroup -o edit -a usernametoadd -t user admin
sudo dseditgroup -o edit -a usernametoadd -t user wheel