Simplify all scalar expressions appearing in the Matrix.

def simplify_scalar(self, func=sympy.simplify):
        """Simplify all scalar expressions appearing in the Matrix."""

        def element_simplify(v):
            if isinstance(v, sympy.Basic):
                return func(v)
            elif isinstance(v, QuantumExpression):
                return v.simplify_scalar(func=func)
            else:
                return v

        return self.element_wise(element_simplify)