diff --git a/ueb3.tex b/ueb3.tex index 41efa54..dd6fef9 100644 --- a/ueb3.tex +++ b/ueb3.tex @@ -2,14 +2,109 @@ %\pagebreak \chapter{Quantenmechanik I - Übungsblatt 3} +Zugehörige Voraussetzungen: +Operatoren +Wahrscheinlichkeiten + \section{Aufgabe 7: Eigenzustände und Erwartungswerte von Spin-1/2-Teilchen} +$\vec{n}(\theta,\Phi) = \inlinematrix{\sin(\theta) \cos(\Phi) \\ \sin(\theta) \sin(\Phi) \\ \cos(\Phi)}$ \\ +Präparation in $\ket{n_1+} \vec{n_1} = \vec{n}(\frac{\pi}{4},\frac{\pi}{4})$ \\ +$\Rightarrow$ \\ +$\vec{n_1} = \inlinematrix{\cos(\frac{\pi}{4} \\ 1 \\ \cos(\frac{\pi}{4}}$ +$\ket{n_1} = \inlinematrix{\cos(\frac{\Thea}{2}) \\ e^{\i \phi} \sin(\frac{\Theta}{2}}$ + \subsection*{a)} +$\vec{n_2} = \vec{n}(\frac{3\pi}{4},\phi)$ +\begin{align} + p_+(\phi) &= \probb{\sigma_{n_2 \cequiv +1}{\ket{n_1+}}} \\ + &= \abs{\braket{n_2+}{n_1+}}^2 \\ + &= \frac{1}{4} \sbk{1 + \cos(\phi+\frac{\pi}{4})} \\ + p_-(\phi) &= 1 - p_+ \\ + &= 1 - \frac{1}{4} \sbk{1 + \cos(\phi+\frac{\pi}{4})} \\ + &= \frac{3}{4} - \frac{1}{4} \cos(\phi+\frac{\pi}{4}) \\ + &= \frac{1}{4} \sbk{3 - \cos(\phi+\frac{\pi}{4})} + \ket{n_1+} &= c_1 \ket{n_2+} + c_2 \ket{n_2-} +\end{align} + \subsection*{b)} + \begin{align} + \expval{şigma_z}_{\ket{n_1+}} &= \probb{\sigma_z \cequiv +1}{\ket{n_1+}} + + (-1) \probb{\sigma_z \cequiv -1}{\ket{n_1+}} \\ \\ + &= \abs{\inlinematrix{1 & 0} \inlinematrix{\cos(\frac{\pi}{8} \\ e^{\i \frac{\pi}{4}}}}^2 - + \abs{\inlinematrix{0 & -1} \inlinematrix{\cos(\frac{\pi}{8} \\ e^{\i \frac{\pi}{4}}}}^2 \\ + &= \cos^2(\frac{\pi}{8}) - \sin^2(\frac{\pi}{8}) \\ + &= \cos(\frac{\pi}{4} \\ + &= \frac{\sqrt{2}}{2} \\ + \sbk{\Delta \sigma_x}^2 &= \prob{\sigma_x^2} - \prob{\sigma_x}^2 \\ + \dirac{n_1+}{\sigma_x}{n_1+} &= \sin(\frac{\pi}{4} \cos(\frac{\pi}{4} &= \frac{1}{2} \\ + \dirac{n_1+}{\sigma_x^2}{n_1+} &= \inlinematrix{\cos(\frac{\pi}{8}) & e^{-\frac{\pi}{4}} \sin(\frac{\pi}{8})} \cdot + \inlinematrix{1 & 0 \\ 1 & 0} \cdot + \inlinematrix{\cos(\frac{\pi}{8}) \\ e^{\frac{\pi}{4}} \sin(\frac{\pi}{8})} \\ + &\Rightarrow + \sbk{\Delta \sigma_x}^2 &= 1 - \frac{1}{2}^2 \\ + &= \frac{3}{4} \\ + &\stackrel{analog}{=} \sbk{\Delta \sigma_y}^2 \\ + \sbk{\Delta \sigma_x} \cdot \sbk{\Delta \sigma_y} &= \frac{3}{4} \\ + \sbk{\Delta A} \cdot \sbk{\Delta B} &\geq \frac{1}{2} \abs{\expval{\frac{1}{\i} [A,B]}} \\ + \frac{1}{2} \abs{\expval{\sigma_z}} &= \frac{1}{\sqrt{2}} &\< \frac{3}{4} + \end{align} + \subsection*{c)} +\begin{align} + \ket{\Psi} &= N (\ket{Z+} + e^{\i \alpha} \ket{Z-}) = N \inlinematrix{1 \\ e^{\i \alpha}} \\ + \braket{\Psi}{\Psi} &= 1 \\ + N^2 \sbk{1 + e^{\i \alpha - \i \alpha)}} &\deq 1 \\ + &\Rightarrow \\ + N &= \frac{1}{\sqrt{2}} \\ \\ + P_+ &= \abs{\braket{x+}{\Psi}}^2 \\ + &= \abs{\frac{1}{\sqrt{2}} \inlinematrix{1 \\ 1} \cdot \frac{1}{\sqrt{2}} \inlinematrix{1 \\ e^{\i \alpha}}}^2 \\ + &= \frac{1}{4} \abs{1 + e^{\i \alpha}}^2 \\ + &= \frac{1}{2} \sbk{1 + \cos(\alpha)} + +\end{align} + \section{Aufgabe 8: Teilchen mit Spin 1} \subsection*{a)} +\includegraphics{grafiken/U_A6_a.pdf} \subsection*{b)} +$[\Epsilon_\alpha, \Epsilon_\beta] = \i \Epsilon_{\alpha, \beta, \gamma} \Epsilon_\gamma$ +mit allen $\Sigma_{x,y,z}$ durch testen. \subsection*{c)} +\begin{align} + \Sigma_^2 &= \Sigma_x^2 + \Sigma_y^2 + \Sigma_z^2 \\ + &= 2 \one +\end{align} + \subsection*{d)} -\subsection*{e)} \ No newline at end of file +\begin{math} + \ket{x+}, \ket{x-}, \ket{x0}, \ket{\Psi} = \ket{n_0}, n(\Theta,\Phi) +\end{math} +\begin{align} + p_0 &\Rightarrow &\ket{x0} &= \frac{1}{\sqrt{2}} \cdot \inlinematrix{1 \\ 0 \\ -1} \\ + p_+ &\Rightarrow &\ket{x+} &= \frac{1}{2} \cdot \inlinematrix{1 \\ \frac{1}{\sqrt{2}} \\ 1} \\ + p_- &\Rightarrow &\ket{x-} &= \frac{1}{2} \cdot \inlinematrix{-1 \\ \frac{1}{\sqrt{2}} \\ -1} + \vec{\Sigma_n} &= &\Sigma \cdot \vev{n} &= \inlinematrix{\cos(\Theta) & \frac{1}{\sqrt{2}} \sin(\Theta) e^{-\ \phi} & 0 \\ + \frac{1}{\sqrt{2}} \sin(\Phi) e^{\i \phi} & 0 & \frac{1}{\sqrt{2}} \sin(\Theta) e^{-\i \phi} \\ + 0 & \frac{1}{\sqrt{2}} \sin(\Theta) e^{\i \phi} & \cos(\Theta)} + &\Rightarrow + \ket{n_0} & & &= \frac{1}\sqrt{2}} \inlinematrix{-\sin(\Theta) e^{\i \Phi} \\ \sqrt{2} \cos(\Theta) \\ \sin(\Theta) e^{\i \Phi}} \\ +\end{align} +\begin{align} + p_+ &= \abs{\braket{x_1}{n_0}}^2 &= \ldots \frac{1}{2} \cos^2(\Theta) + \frac{1}{2} \sin^2(\Theta) \sin^2(\Phi) = p_- \\ + p_0 &= 1- 2 p_+ &= 1 - 2 p_- +\end{align} + +\subsection*{e)} +\begin{align} + \expval{\Sigma_x}_{\ket{\Psi}} &= \dirac{n_0}{\Sigma_x}{n_0} \\ + &= +1 + 1 p_+ + p_0 + (-1) p_- \\ + &= 0 \\ + \ket{\Psi} &= c_1 \ket{\x+} + c_2 \ket{x-} + c_3 \ket{x0} \\ + \sbk{\Delta \Epsilon_x}^2 &= \langle \Sigma_x^2 \rangle - {\langle \Sigma_x \rangle}^2 \\ + &= c_2 \inlinematrix{1 & 0 & 1 \\ 0 & 2 & 0 \\ 1 & 0 & 1} %ist das richtig? + \dirac{\Psi}{\Sigma_x^2}{\Psi} &= c_1^2 \cdot 1^2 + c_2^2 \cdot (-1)^2 + c_3^2 \cdot 0^2 \\ + &\stackrel{c_1 = c_2}{=} 2 c_1^2 \\ + &= \cos^2(\Theta) + \sin^2(\Theta) \cdot \sin^2(\phi) %Ist das richtig? + +\end{align}