The concept you're referring to is not specifically a part of quantum physics, but rather an idea from speculative theories such as the "many-worlds interpretation" of quantum mechanics. In quantum physics, the many-worlds interpretation proposes that all possible outcomes of a quantum event actually occur in separate branches or universes. This means that whenever a measurement is made, the universe splits into multiple copies, each corresponding to a different outcome.
According to this interpretation, every conceivable outcome of a quantum event exists in a different universe. For example, if there is a quantum event with two possible outcomes, such as the spin of an electron being up or down, the many-worlds interpretation suggests that each outcome is realized in a separate universe. In one universe, the electron's spin is up, while in another universe, the spin is down.
It's important to note that the many-worlds interpretation is just one of several interpretations of quantum mechanics. Other interpretations, such as the Copenhagen interpretation, do not involve the notion of multiple universes and instead focus on the probabilistic nature of quantum events.
The idea of alternative universes or parallel realities extends beyond quantum physics into various works of science fiction and speculative thought. While it's an intriguing concept, it's currently purely theoretical and not supported by direct empirical evidence.