Add abstract

src/thesis/chapters/5_conclusion_and_outlook.tex

@@ -72,10 +72,10 @@ performance difference was most pronounced at low numbers of maximum iterations.
 % Implications from experimental results
 
 These observations imply that the warm-start modification to
-sliding-window decoding provides a universal improvement, as long as
+sliding-window decoding provides a consistent improvement, as long as
 some care is taken with specifying the information to be passed to
 the subsequent window.
-Not that this comes at no additional cost to the decoding complexity,
+Note that this comes at no additional cost to the decoding complexity,
 since the only difference between warm- and cold-start sliding-window
 decoding is the initialization of the \ac{bp} messages.
 We expect similar behavior with other inner decoders that support

src/thesis/chapters/abstract.tex

@@ -0,0 +1,56 @@
+\chapter*{Abstract}
+
+% Current state of the art
+
+\Ac{qec} protects fragile quantum states against decoherence by
+encoding logical information into a larger number of physical qubits.
+Because the syndrome extraction circuitry is itself implemented on
+noisy quantum hardware, practical \ac{qec} must be fault-tolerant,
+accounting for errors introduced by the correction procedure itself.
+Fault tolerance considerations and the syndrome extraction circuit
+are captured by \acp{dem}, which provide a unified framework for passing
+this information to the decoder.
+
+Accounting for fault tolerance substantially inflates the
+decoding problem.
+At the same time, \ac{qec} imposes strict latency constraints due to
+the backlog problem, where syndrome data accumulates faster than it
+can be decoded.
+Together, these factors pose a serious challenge for practical decoders.
+Sliding-window decoding addresses this challenge by exploiting the
+repeated structure of the syndrome extraction circuitry, partitioning
+the \ac{dem}'s check matrix into overlapping windows that can be
+decoded sequentially.
+This allows for an earlier start to the decoding process, before all
+syndrome measurements have been completed, thereby lowering the latency.
+
+% Our work: Identify research gap
+
+In this thesis, we perform a review of the existing literature on
+sliding-window decoding and draw an analogy to windowed
+decoding for classical spatially-coupled low-density parity-check
+(\acs{sc}-\acs{ldpc}) codes.
+We recognize that in contrast to the latter, existing realizations
+of sliding-window decoding for \ac{qec} discard the soft information
+produced inside one window before moving to the next.
+
+% Our work: Warm-start
+
+% TODO: Quantify improvement. Also for conclusion
+We propose warm-start sliding-window decoding, in which the
+\ac{bp} messages on the edges crossing into the overlap region of the previous
+window are reused to initialize the corresponding messages of the
+next window.
+The warm start is formulated first for plain \ac{bp} and then extended to
+\ac{bp} with guided decimation (\acs{bpgd}).
+For both plain min-sum \ac{bp} and \ac{bpgd} decoding, the warm-start
+initialization provides a consistent improvement across all examined
+parameter settings.
+We attribute this to an effective increase in \ac{bp} iterations on
+variable nodes in the overlap regions: each such VN is processed by
+multiple consecutive windows, and warm-starting lets these
+invocations accumulate iterations rather than restart from scratch.
+Crucially, the warm-start modification incurs no additional
+computational cost relative to cold-start decoding, as it differs
+only in the initialization of the \ac{bp} messages.
+

src/thesis/main.tex

@@ -103,7 +103,7 @@
 \maketitle
 \newpage
 
-% \include{chapters/abstract}
+\include{chapters/abstract}
 
 \cleardoublepage
 \pagenumbering{arabic}