Quantum information cannot be copied
When you want to share a photo with a friend or send a poem to your mother, you simply copy and paste the information. However, in quantum, copying information is physically impossible. This is called the No-Cloning theorem.
Suppose the No-Cloning principle did not exist, and you would have been able to clone an unknown quantum state. The quantum state is in an unknown superposition of the 0 and 1 state. How would you find out the weights of the superposition, i.e. the respective probabilities of finding the state in 0 or 1?
See the Wikipedia page on the No-cloning theorem for the mathematical proof: https://en.wikipedia.org/wiki/No-cloning_theorem