Many-worlds interpretation

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Quantum mechanics
${\displaystyle i\hbar {\frac {d}{dt}}|\Psi \rangle ={\hat {H}}|\Psi \rangle }$ Schrödinger equation
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The many-worlds interpretation (MWI) is an interpretation of quantum mechanics that asserts that the universal wavefunction is objectively real, and that there is no wave function collapse.^[1] This implies that all possible outcomes of quantum measurements are physically realized in different "worlds".^[2] The evolution of reality as a whole in MWI is rigidly deterministic^[1]: 9 and local.^[3] Many-worlds is also called the relative state formulation or the Everett interpretation, after physicist Hugh Everett, who first proposed it in 1957.^[4][5] Bryce DeWitt popularized the formulation and named it many-worlds in the 1970s.^[6][1][7][8]

In modern versions of many-worlds, the subjective appearance of wave function collapse is explained by the mechanism of quantum decoherence.^[2] Decoherence approaches to interpreting quantum theory have been widely explored and developed since the 1970s.^[9][10][11] MWI is considered a mainstream interpretation of quantum mechanics, along with the other decoherence interpretations, the Copenhagen interpretation, and hidden variable theories such as Bohmian mechanics.^[12][2]

The many-worlds interpretation implies that there are many parallel, non-interacting worlds. It is one of a number of multiverse hypotheses in physics and philosophy. MWI views time as a many-branched tree, wherein every possible quantum outcome is realized. This is intended to resolve the measurement problem and thus some paradoxes of quantum theory, such as Wigner's friend,^[4]: 4–6 the EPR paradox^{[5]: 462 [1]: 118} and Schrödinger's cat,^[6] since every possible outcome of a quantum event exists in its own world.