Hi Morihisa
if you have a 10GbE switch and 40GbE port, you can use QSA (QSFP -> SFP+ adapter) or QSFP to SFP cable, to reduce the speed of the adapter from 40GbE to 10GbE.
The is no way to create 4 logical ports of 10GbE from one 40GbE physical port of the adapter.
Can you share your need/setup?
Thanks,
Ophir.