From 62b4d4838b463f31cc3ce01f70e6ffd1be59a95a Mon Sep 17 00:00:00 2001 From: Andreas Tsouchlos Date: Wed, 29 Apr 2026 18:24:21 +0200 Subject: [PATCH] Write stim subsection --- src/thesis/chapters/3_fault_tolerant_qec.tex | 41 +++++++++++++------- 1 file changed, 27 insertions(+), 14 deletions(-) diff --git a/src/thesis/chapters/3_fault_tolerant_qec.tex b/src/thesis/chapters/3_fault_tolerant_qec.tex index 63d5c98..08171af 100644 --- a/src/thesis/chapters/3_fault_tolerant_qec.tex +++ b/src/thesis/chapters/3_fault_tolerant_qec.tex @@ -1045,8 +1045,6 @@ circuit-level noise model to the same value, the physical error rate $p$. % Per-round LER -\content{Introduce logical error rate} - % TODO: Introduce the logical error rate Another aspect that is important to consider is the meaning of the logical error rate in the context of a \ac{qec} system with multiple @@ -1101,20 +1099,35 @@ topic to our own work. \subsection{Stim} \label{subsec:Stim} -As we noted in \autoref{subsec:Measurement Syndrome Matrix}, to -obtain a measurement syndrome matrix we must propagate Pauli frames +It is not immediately apparent how the \ac{dem} will look from looking +at a code's \ac{pcm}, because it heavily depends on the exact circuit +construction and choice of noise model. +As we noted in \autoref{subsec:Measurement Syndrome Matrix}, we can +obtain a measurement syndrome matrix by propagating Pauli frames through the circuit. -\red{[This is where stim comes into play]} +The standard choice of simulation tool used for this purpose is +\emph{stim}% +\footnote{https://github.com/quantumlib/Stim} +\cite{gidney_stim_2021}, which is available as a Python 3 +pypi package. +In fact, it was in this tool that the concept of the \ac{dem} was +first introduced. -\content{Circuit code heavily depends on the exact circuit construction} -\content{Not easy to predict how errors at different locations -propagate through the circuit an what detectors they affect} +One capability of stim, and \acp{dem} in general, that we didn't go +into detail about in this chapter is the merging of error mechanisms. +Since \acp{dem} differentiate errors based on their effect on the +measurements and not on their type and location, it is natural to +group errors that have the same effect. +This slightly lowers the computational complexity of decoding, as the +number of resulting \acp{vn} is reduced. -\content{Merging of error mechanisms} +While stim is a useful tool for circuit simulation, it doesn't +include many utilities for building syndrome extraction circuitry automatically. +The user has to define most, if not, all of the circuit manually, +depending on the code in question. +This is somewhat natural, as stim is meant first and foremost as a +simulator, and circuit generation is contigent upon the \ac{qec} +scheme in question. -\content{Stim is were DEMs were first introduced} - -\content{Stim is a software package that generates DEMs from circuits} -\content{The user still has to define the circuit themselves, and -especially the detectors \cite[Sec~2.5]{derks_designing_2025}} +\content{Introduce logical error rate}