fixing latex

pennylane/fermi/fermionic.py

@@ -331,10 +331,12 @@ def shift_operator(self, initial_position, final_position):
 
  .. math::
 
- a_0 a_1 = -a_1 a_0\\
- a^{\dagger}_0 a^{\dagger}_1 = -a^{\dagger}_1 a^{\dagger}_0\\
- a_0 a^{\dagger}_1 = -a^{\dagger}_1 a_0\\
- a_0 a^{\dagger}_0 = 1 - a^{\dagger}_0 a_0
+ \begin{align*}
+ a_0 a_1 &= -a_1 a_0\\
+ a^{\dagger}_0 a^{\dagger}_1 &= -a^{\dagger}_1 a^{\dagger}_0\\
+ a_0 a^{\dagger}_1 &= -a^{\dagger}_1 a_0\\
+ a_0 a^{\dagger}_0 &= 1 - a^{\dagger}_0 a_0
+ \end{align*}
 
 
  For more details see `Wikipedia <https://en.wikipedia.org/wiki/Creation_and_annihilation_operators#Creation_and_annihilation_operators_in_quantum_field_theories>`_.