David Deutsch, Simon Saunders and David Wallace of the University of Oxford may have found support for the idea of parallel universes. According to their research, the mathematics of parallel universes give rise to key equations of quantum mechanics.

50 years ago, Hugh Everett, a graduate student at Princeton University, proposed the “many worlds” interpretation of quantum mechanics.  This interpretation states that the rules of quantum mechanics apply to both the subatomic quantum world and our larger-scale world. This would mean that, like Schrodinger’s cat, the universe would have to exist in multiple states.  There would be a multiverse full of parallel universes, one for each physical possibility. 

One of the problems of the many worlds theory has been that it has no place for the Born rule. The Born rule says that scientists can predict the probability of getting a certain outcome by the square of its wave function.  While the Born rule fits experimental observations, probability does not have a place in the multiverse at all.  According to Everett’s interpretation, if you toss a coin, it must come up both heads and tails.  Saying that the probability of it coming up heads is 50 per cent is meaningless. 

In the mid-1990s, Deutsch and his team decided to put the uncertainty of quantum mechanical experiments back into the many worlds scenario by examining a quantum experiment while accepting the many worlds interpretation and excluding probability theory.

As the universe splits into parallel versions of itself, it creates a branching multiverse.  The branches’ thickness can be calculated using deterministic equations alone. This avoids the uncertainties that are normally associated with quantum physics. Deutsch’s team found that the branching structure exactly reproduces the probabilities predicted by the Born rule. The branching structure also creates the illusion of probabilistic outcomes to measurements.

While some physicists say that the work of Deutsch, Saunders and Wallace has caused them to accept the many worlds theory, David Albert of Columbia University, New York says that it is irrelevant that the branching universes give the illusion of probabilistic outcomes.  The reason that the branching occurs in the first place is what is important.