www.canada.ca/en/immigration-refugees-citizenship/services/visit-canada/minor-children-travelling-canada.html
If a minor child is travelling alone
The child should present
their own passport
A parent’s passport, even if the child’s details are included in it, cannot be used.
a copy of their birth certificate, and
a letter of authorization, in English or French if possible, which is signed by both parents or by their legal guardian and includes
the parents’ (or legal guardian’s) address and telephone number, and
the name, address and telephone number of the adult who will look after the child in Canada