handle precision edge cases

qiskit/visualization/array.py

@@ -37,6 +37,14 @@ def num_to_latex(raw_value, precision=15, coefficient=False, first_term=True):
 
     raw_value = np.around(raw_value, precision)
     value = sympy.nsimplify(raw_value, rational=False)
+
+    if isinstance(value, sympy.core.numbers.Rational) and value.denominator > 50:
+        # Avoid showing ugly fractions (e.g. 50498971964399/62500000000000)
+        value = value.evalf()  # Display as float
+
+    if isinstance(value, sympy.core.numbers.Float):
+        value = round(value, precision)
+
     element = sympy.latex(value, full_prec=False)
 
     if not coefficient:

qiskit/visualization/state_visualization.py

@@ -1220,6 +1220,7 @@ def _state_to_latex_ket(data, max_size=12, precision=15):
         data: State vector
         max_size: Maximum number of non-zero terms in the expression. If the number of
                  non-zero terms is larger than the max_size, then the representation is truncated.
+        precision (int): Number of decimal places to round each amplitude to.
 
     Returns:
         String with LaTeX representation of the state vector

test/python/visualization/test_state_latex_drawer.py

@@ -121,7 +121,7 @@ def test_number_to_latex_terms(self):
             ([1 + np.sqrt(2)], ["(1 + \\sqrt{2})"]),
         ]
         for numbers, latex_terms in cases:
-            terms = numbers_to_latex_terms(numbers, 15)
+            terms = numbers_to_latex_terms(numbers)
             self.assertListEqual(terms, latex_terms)