- #1
Taylor_1989
- 402
- 14
Homework Statement
I am having a issue with how my lecture has normalised the energy state in this question.
I will post my working and I will print screen his solution to the given question below, we have the same answer but I am unsure to why he has used the ratio method.
Q4. a), b), c)
Homework Equations
The Attempt at a Solution
My solution for a), b), c)
a)
$$\hat H|E> = E|E> ;[1]$$
$$\hat H|E> - E|E>=0 ;[2]$$
$$\hat H|E> - IE|E>=0; [3]$$
$$(\hat H-IE)=0 ;[4]$$
$$\begin{pmatrix}0&-\Omega \\ \:-\Omega &\frac{2\Omega }{\sqrt{3}}\end{pmatrix}-E\begin{pmatrix}1&0\\ \:0&1\end{pmatrix}=0 ;[5] $$
So expanding out and finding the determinate of the following matrix
$$\begin{pmatrix}-E&-\Omega \\ \:-\Omega &\frac{2\Omega }{\sqrt{3}}-E\end{pmatrix}=0 ; [6]$$
$$\begin{pmatrix}-E&-\Omega \\ \:-\Omega &\frac{2\Omega }{\sqrt{3}}-E\end{pmatrix}= E^2-\frac{2E\Omega }{\sqrt{3}}-\Omega ^2=0 ;[7]$$
$$\left(E-\frac{3\Omega }{\sqrt{3}}\right)\left(E+\frac{\Omega }{\sqrt{3}}\right)=0 [8]$$
So solving gives me the following for ##E_{-}## and ##E_{+}##
$$E_{-}=\frac{3\Omega }{\sqrt{3}} ; [9]$$
$$E_{+}=-\frac{\Omega }{\sqrt{3}} ; [10]$$
b) I solved the eignvector for ground state in the following way
$$\begin{pmatrix}0&-\Omega \\ -\Omega &\frac{2\Omega }{\sqrt{3}}\end{pmatrix}\begin{pmatrix}A\\ B\end{pmatrix}=-\frac{\Omega }{\sqrt{3}}\begin{pmatrix}A\\ B\end{pmatrix} ; [11] $$
$$-\Omega B= -\frac{\Omega }{\sqrt{3}}A ; [12]$$
$$-\Omega A=-\frac{3}{\sqrt{3}}B ; [13]$$
So solving for both of these give ##A=\sqrt 3## so therfore:
$$E_{-}= |0> + \sqrt 3 |1> ; [14]$$
To normalize [14] I found the normalizing constant in the following way:
$$< E_{-} | E_{-} > = 1+3=4 ; [15]$$
$$N^2 < E_{-} | E_{-} > = 1 ; [16]$$
$$N^2=\frac{1}{4}; [17]$$
$$N= \frac{1}{2}; [18]$$
$$|E_{-}> = \frac{1}{2} |0> + \frac{\sqrt 3}{2} | 1 > ; [19]$$
c) $$P(1)=\left(\frac{\sqrt{3}}{2}\right)^2=\frac{3}{4}=75\% [20]$$
Here is my lecture solution:
a)
b)
I just don't understand the ratio method, it is a quicker method than mine or is it used more in more difficult matrices