In these source examples, the completed action is close or relevant to the present.
قَدْ فَرِقَ الْوَلَدُ — The boy has become afraid.
قَدْ شَرِبْنَا اللَّبَنَ — We have drunk the milk.
قَدْ طَلَعَتِ الشَّمْسُ — The sun has risen.
Notice that English uses a natural present-perfect form rather than inserting one fixed translation for قَدْ.