Update src/qibo/quantum_info/metrics.py

Co-authored-by: Matteo Robbiati <[email protected]>

src/qibo/quantum_info/metrics.py

@@ -1157,16 +1157,16 @@ def frame_potential(
     For :math:`n` qubits and moment :math:`t`, the frame potential
     :math:`\\mathcal{F}_{\\mathcal{U}}^{(t)}` if given by [1]
 
-    ..math::
+    .. math::
         \\mathcal{F}_{\\mathcal{U}}^{(t)} = \\int_{U,V \\in \\mathcal{U}} \\,
-            dU \\, dV \\, \\abs{\\tr(U^{\\dagger} \\, V)}^{2t} \\, ,
+            \\text{d}U \\, \\text{d}V \\, \\text{abs}\\bigl[\\text{tr}(U^{\\dagger} \\, V)\\bigr]^{2t} \\, ,
 
     where :math:`\\mathcal{U}` is the group of unitaries defined by the parametrized circuit.
     The frame potential is approximated by the average
 
-    ..math::
+    .. math::
         \\mathcal{F}_{\\mathcal{U}}^{(t)} \\approx \\frac{1}{N} \\,
-            \\sum_{k=1}^{N} \\, \\abs{\\tr(U_{k}^{\\dagger} \\, V_{k})}^{2t} \\, ,
+            \\sum_{k=1}^{N} \\, \\text{abs}\\bigl[ \\text{tr}(U_{k}^{\\dagger} \\, V_{k})\\bigr]^{2t} \\, ,
 
     where :math:`N` is the number of ``samples``.