Pass max_size to Statevector LaTeX drawer (Qiskit#8197)

* Fix Qiskit#7516

* Remove unused import

* Improve splitting of string literals

Co-authored-by: Jake Lishman <[email protected]>
Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

qiskit/visualization/state_visualization.py

@@ -1130,7 +1130,7 @@ def state_to_latex(
     # this means the operator shape should hve no input dimensions and all output dimensions equal to 2
     is_qubit_statevector = len(operator_shape.dims_r()) == 0 and set(operator_shape.dims_l()) == {2}
     if convention == "ket" and is_qubit_statevector:
-        latex_str = _state_to_latex_ket(state._data)
+        latex_str = _state_to_latex_ket(state._data, **args)
     else:
         latex_str = array_to_latex(state._data, source=True, **args)
     return prefix + latex_str + suffix

releasenotes/notes/fix-latex-ket-max-size-f11c3a89215a49e7.yaml

@@ -0,0 +1,5 @@
+---
+fixes:
+  - |
+    Fixed a bug in which the latex state vector drawer ignores the `max_size`
+    parameter.

test/python/visualization/test_state_latex_drawer.py

@@ -0,0 +1,51 @@
+# This code is part of Qiskit.
+#
+# (C) Copyright IBM 2022.
+#
+# This code is licensed under the Apache License, Version 2.0. You may
+# obtain a copy of this license in the LICENSE.txt file in the root directory
+# of this source tree or at http://www.apache.org/licenses/LICENSE-2.0.
+#
+# Any modifications or derivative works of this code must retain this
+# copyright notice, and modified files need to carry a notice indicating
+# that they have been altered from the originals.
+
+"""Tests for visualization of latex state and unitary drawers"""
+
+import unittest
+
+from qiskit.quantum_info import Statevector
+from qiskit.visualization.state_visualization import state_drawer
+from .visualization import QiskitVisualizationTestCase
+
+
+class TestLatexStateDrawer(QiskitVisualizationTestCase):
+    """Qiskit state and unitary latex drawer."""
+
+    def test_state(self):
+        """Test latex state vector drawer works with default settings."""
+
+        sv = Statevector.from_label("+-rl")
+        output = state_drawer(sv, "latex_source")
+        expected_output = (
+            r"\frac{1}{4} |0000\rangle- \frac{i}{4} |0001\rangle+\frac{i}{4} |0010\rangle"
+            r"+\frac{1}{4} |0011\rangle- \frac{1}{4} |0100\rangle+\frac{i}{4} |0101\rangle"
+            r" + \ldots +\frac{1}{4} |1011\rangle- \frac{1}{4} |1100\rangle"
+            r"+\frac{i}{4} |1101\rangle- \frac{i}{4} |1110\rangle- \frac{1}{4} |1111\rangle"
+        )
+        self.assertEqual(output, expected_output)
+
+    def test_state_max_size(self):
+        """Test `max_size` parameter for latex ket notation."""
+
+        sv = Statevector.from_label("+-rl")
+        output = state_drawer(sv, "latex_source", max_size=4)
+        expected_output = (
+            r"\frac{1}{4} |0000\rangle- \frac{i}{4} |0001\rangle"
+            r" + \ldots - \frac{1}{4} |1111\rangle"
+        )
+        self.assertEqual(output, expected_output)
+
+
+if __name__ == "__main__":
+    unittest.main(verbosity=2)