Solution
= Solution
The displacement operator is unitary, so $\||\alpha\rangle\|=1$. By <coherent state>, $A|\alpha\rangle=\alpha|\alpha\rangle$, hence $\|A|\alpha\rangle\|=|\alpha|$.
= Solution
The displacement operator is unitary, so $\||\alpha\rangle\|=1$. By <coherent state>, $A|\alpha\rangle=\alpha|\alpha\rangle$, hence $\|A|\alpha\rangle\|=|\alpha|$.