When describing nature using physical laws, scientists often start from everyday experiences. However, our usual intuition does not apply to the quantum world. Physicists have recently realized that quantum theory even forces us to question innate concepts, such as the order in which things occur. Imagine, for example, a race between two friends, Alice and Bob. In everyday life, the winner is the first to cross the finish line. Thus, common sense says that either Alice wins, Bob wins, or they tie. This reasoning, however, is not always applicable in the quantum world. In fact, quantum mechanics allows each runner to win and lose in one race: Alice could reach the finish line both before and after Bob in quantum superposition. However, even if we held such a quantum race, how could we verify that both racers won in superposition? Part of the problem is that quantum mechanics says when we observe the race it "collapses". This means that we only see either Alice win or lose the race: we can't see the superposition.
Read more at: https://phys.org/news/2017-03-quantum-winner-loser.html#jCp