classical computers store information in bits which can either be 0 or 1, but in quantum computer the qubit can store 0 , 1 or a state that is the superposition of these two states so how this superposition help to use less qubit to stor information for example: how many qubit we are need to store "16"? I know a little about h(x) but i don't know how we store! And is there any fear about losing information because of probability?
You need 4 qubits as in classical physics, the information contained in a qubit is the same as a bit.
The power of quantum computation comes from the operations that you can do in a system without measuring his state, the begin and the end of a "program" have to be classical if you want to get a definite answer.