Fidelity of quantum states

Fidelity of quantum states is how close two quantum states are to each other. It can help scientists measure how similar two quantum states are. For example if one quantum state has a higher fidelity than another, it means that it is closer to the original quantum state. To measure the fidelity, scientists look at how close the probability distribution of one quantum state is to the probability distribution of the other quantum state. If the two probability distributions are very close, then the fidelity is high.