diff --git a/thesis/chapters/graph_simulator.tex b/thesis/chapters/graph_simulator.tex index 4ac9723..4bf551b 100644 --- a/thesis/chapters/graph_simulator.tex +++ b/thesis/chapters/graph_simulator.tex @@ -183,6 +183,8 @@ by the following relation: \end{equation} \end{definition} +Where every $o_i$ acts on the $i$-th qbit. + One can show that any stabilizer state can be realized as a graph state (for instance in \cite{schlingenmann2001}). \subsection{Operations on the Graph State} @@ -219,6 +221,34 @@ than a single qbit gate. % \ifend %\end{struktogramm} + +\subsubsection{Measurement of a Qbit} + +Note that the $Z$ gate is diagonal in the $\{\ket{1}_s,\ket{0}_s\}$ basis with eigen values $1, -1$. +This gives a simple expression for the projector on the $\ket{0}_s$ and $\ket{1}_s$ state of qbit $k$: + +\begin{equation} + \tilde{P^{v}_{k}} := \frac{I_k + (-1)^vZ_k}{2}, v \in {0, 1} +\end{equation} + +This projector trivially commutes with any non-operand vertex operator yielding for a state + + +\begin{equation} + \begin{aligned} + \ket{\psi} := \left(\bigotimes\limits_{\{i,j\} \in E} CZ_{i,j}\right) \ket{+} \\ + \tilde{P^{v}_{k}} \left(\bigotimes\limits_{i=0}{n-1} o_i\right)\ket{\psi} &= + \left(\bigotimes\limits_{i=0,i \ne k}{n-1} o_i\right) \tilde{P^{v}_{k}} o_k \ket{\psi} \\ + &= \left(\bigotimes\limits_{i=0,i \ne k}{n-1} o_i\right) o_ko_k^\dagger \tilde{P^{v}_{k}} o_k \ket{\psi} \\ + &= \left(\bigotimes\limits_{i=0,i \ne k}{n-1} o_i\right) o_k = \frac{I_k + (-1)^v o_k^\dagger Z_ko_k}{2} \ket{\psi} + \end{aligned} +\end{equation} + +Now $o_k$ stabilizes $P$, as it is an element of $C_L$, meaning that $o_k^\dagger Z_k o_k \in \{-1,1\}\{X_k, Y_k, Z_k\}$ +Which gives a new projector on a Pauli matrix: $P_k := o_k^\dagger Z_ko_k$ + + + \subsection{Graph Storage} One of the gread advantages of simulating in the graph formalism is a great increase