diff --git a/k-local-review.pdf b/k-local-review.pdf index 1508d26..38c1433 100644 Binary files a/k-local-review.pdf and b/k-local-review.pdf differ diff --git a/k-local-review.tex b/k-local-review.tex index 1e5e5e6..c15082e 100644 --- a/k-local-review.tex +++ b/k-local-review.tex @@ -1344,6 +1344,82 @@ \subsection{Flag Based SAT Mapping\label{sub:flag_SAT}} \newpage + +\subsection{Chained Three Body Parity Operators} + +\summarysec + +Goal: Terms of the form $z_{a_{k}}=-z_iz_j$ can be chained together to make large product terms consisting of $z$. +%Recall that products of $b$ correspond to parity check or ${\sc xor}$ operations, while products of $b$ correspond to logical ${\sc and}$ operations. +The penalty term $P(z_{a_k},z_i,z_j)= \mp z_{a_k}z_iz_j$ will lead to an energy penalty unless $z_{a_k}=\pm z_iz_j$. The 3-local term can be made from gadgets. + +%This method was originally only used to reproduce the ground state of high locality terms, but states of the "wrong" parity ($q_k=\mp z_iz_j$) will all have the same energy as well, so it reproduces the full spectrum. + + +\costsec +\begin{itemize} +\item The best known gadget for a 3-local Ising term uses one auxilliary qubit. Based on this gadget an $n\ge4$ body Ising term can be made using $3+2(n-4)$ auxilliary qubits. +\end{itemize} + +\prossec +\begin{itemize} +\item Natural transmon implementation \cite{Leib2016}. +\item Chain like structure means that long range connectivity not required. +\end{itemize} + +\conssec +\begin{itemize} +\item Reproduces energy spectrum, but not with the same degeneracy as the original Hamiltonian. +\item Not very symmetric. +\end{itemize} + +\vspace{-1mm} + +\examplesec +\vspace{-4mm} + +\begin{align} +\begin{gathered} +H_\textrm{5-local} = z_1z_2z_3z_4z_5 =32\,b_1b_2b_3b_4b_5\nonumber \\ +-16\,(b_1b_2b_3b_4+b_1b_2b_3b_5+b_1b_2b_4b_5+b_1b_3b_4b_5+b_2b_3b_4b_5) \nonumber \\ ++8\,(b_1b_2b_3+b_1b_2b_4+b_1b_2b_5+b_1b_3b_4+b_1b_3b_5+b_1b_4b_5+b_2b_3b_4+b_2b_3b_4+b_2b_4b_5+b_3b_4b_5)\nonumber \\ +-4\,(b_1b_2+b_1b_3+b_1b_4+b_1b_5+b_2b_3+b_2b_4+b_2b_5+b_3b_4+b_3b_5+b_4b_5)\nonumber \\ ++2(b_1+b_2+b_3+b_4+b_5)-1 +\end{gathered} +\end{align} + +The full spectrum of $\pm z_1z_2z_3=\pm(8\,b_1b_2b_3-4\,b_1b_2-4\,b_2b_3+2\,b_1+2\,b_2+2\,b_3-1) $ is reproduced by: + +%\begin{equation} +%P_\pm(z_1,z_2,z_3;\lambda)=\lambda\left(z_1z_2+z_2z_3+z_3z_1+2z_a(z_1+z_2+z_3)\right)\mp (z_1+z_2+z_3 +2z_a). +%\end{equation} + +\begin{align} +P_\pm(b_1,b_2,b_3)=\left(4\,(b_1b_2+b_2b_3+b_3b_1)+8\,b_a(b_1+b_2+b_3)-12\,b_a-4\,(b_1+b_2+b_3)+3\right)\nonumber \\ +\mp (2\,b_1+2\,b_2+2\,b_3 +4\,b_a-5). +\end{align} + +This can be written more compactly in terms of $z$: + +\begin{equation} +P_\pm(z_1,z_2,z_3)=\left(z_1z_2+z_2z_3+z_3z_1+2z_a(z_1+z_2+z_3)\right)\mp (z_1+z_2+z_3 +2z_a). +\end{equation} + +Using three copies of this 3-local gadget as a building block, and using two additional auxilliary variables, the spectrum of the 5-local term $z_1z_2z_3z_4z_5$ can be reproduced by the following Hamiltonian + +\begin{equation} +H_{2-\rm{local}}=P_-(b_1,b_2,b_{a_1})+P_-(b_{a_1},b_3,b_{a_2})+P_-(b_{a_2},b_4,b_5). +\end{equation} + +\refsec +\begin{itemize} +\item Proposal with transmon implementation: \cite{Leib2016}. +\item Three local gadget independently discovered: \cite{Chancellor2016}. +\item Extension relating to stabilizers: \cite{Rocchetto2016}. +\end{itemize} + +\newpage +%======= % \subsection{Chained Three Body Parity Operators} % % \summarysec @@ -1416,6 +1492,7 @@ \subsection{Flag Based SAT Mapping\label{sub:flag_SAT}} % \end{itemize} % % \newpage +%>>>>>>> 124543eb8af7ee94a551a5f88571879c749f8386 % \subsection{Multibody Operators in PAQC} %