Add LightSABRE citation to sabre documentation (#13160)

* Add LightSABRE citation to sabre documentation

We recently published a pre-print of a new paper that describes all the
improvements we've developed ontop of the original SABRE algorithm as
part of Qiskit's implementation. This commit adds a citation for that
new paper to the documentation of the two sabre passes in qiskit to
better document how the pass works in practice.

* Add missing citation to SabrePreLayout and fix formatting in SabreSwap

* Tweak wording in sabre swap docstring

qiskit/transpiler/passes/layout/sabre_layout.py

@@ -101,7 +101,10 @@ class SabreLayout(TransformationPass):
 
     **References:**
 
-    [1] Li, Gushu, Yufei Ding, and Yuan Xie. "Tackling the qubit mapping problem
+    [1] Henry Zou and Matthew Treinish and Kevin Hartman and Alexander Ivrii and Jake Lishman.
+    "LightSABRE: A Lightweight and Enhanced SABRE Algorithm"
+    `arXiv:2409.08368 <https://doi.org/10.48550/arXiv.2409.08368>`__
+    [2] Li, Gushu, Yufei Ding, and Yuan Xie. "Tackling the qubit mapping problem
     for NISQ-era quantum devices." ASPLOS 2019.
     `arXiv:1809.02573 <https://arxiv.org/pdf/1809.02573.pdf>`_
     """

qiskit/transpiler/passes/layout/sabre_pre_layout.py

@@ -31,6 +31,11 @@ class SabrePreLayout(AnalysisPass):
     ``sabre_starting_layouts`` (``list[Layout]``)
         An optional list of :class:`~.Layout` objects to use for additional Sabre layout trials.
 
+    **References:**
+
+    [1] Henry Zou and Matthew Treinish and Kevin Hartman and Alexander Ivrii and Jake Lishman.
+    "LightSABRE: A Lightweight and Enhanced SABRE Algorithm"
+    `arXiv:2409.08368 <https://doi.org/10.48550/arXiv.2409.08368>`__
     """
 
     def __init__(

qiskit/transpiler/passes/routing/sabre_swap.py

@@ -41,8 +41,9 @@ class SabreSwap(TransformationPass):
     r"""Map input circuit onto a backend topology via insertion of SWAPs.
 
     Implementation of the SWAP-based heuristic search from the SABRE qubit
-    mapping paper [1] (Algorithm 1). The heuristic aims to minimize the number
-    of lossy SWAPs inserted and the depth of the circuit.
+    mapping paper [2] (Algorithm 1) with the modifications from the LightSABRE
+    paper [1]. The heuristic aims to minimize the number of lossy SWAPs inserted
+    and the depth of the circuit.
 
     This algorithm starts from an initial layout of virtual qubits onto physical
     qubits, and iterates over the circuit DAG until all gates are exhausted,
@@ -69,7 +70,10 @@ class SabreSwap(TransformationPass):
 
     **References:**
 
-    [1] Li, Gushu, Yufei Ding, and Yuan Xie. "Tackling the qubit mapping problem
+    [1] Henry Zou and Matthew Treinish and Kevin Hartman and Alexander Ivrii and Jake Lishman.
+    "LightSABRE: A Lightweight and Enhanced SABRE Algorithm"
+    `arXiv:2409.08368 <https://doi.org/10.48550/arXiv.2409.08368>`__
+    [2] Li, Gushu, Yufei Ding, and Yuan Xie. "Tackling the qubit mapping problem
     for NISQ-era quantum devices." ASPLOS 2019.
     `arXiv:1809.02573 <https://arxiv.org/pdf/1809.02573.pdf>`_
     """