Many-Worlds Interpretation

Overview

The Many-Worlds Interpretation (MWI) is an interpretation of quantum mechanics that asserts the objective reality of the universal wavefunction, but denies the actuality of wavefunction collapse. This interpretation is also known as the relative state formulation or the Everett interpretation, after physicist Hugh Everett III, who first proposed it in 1957. MWI implies that all possible outcomes of quantum measurements are physically realized in some "world" or universe.

History

Hugh Everett III, who was a graduate student at Princeton at the time, first proposed the Many-Worlds Interpretation in his doctoral thesis, "The Theory of the Universal Wave Function". His work was supervised by John Archibald Wheeler, a notable physicist known for his work in general relativity. Everett's interpretation was a radical departure from the then-dominant Copenhagen interpretation, which posited a wavefunction collapse when a measurement is made.

Basic Principles

The Many-Worlds Interpretation is grounded in several key principles. First, it asserts the complete physical reality of the wavefunction. In this view, the wavefunction is not just a mathematical tool for predicting the outcomes of measurements, but a real, physical entity. Second, it denies the actuality of wavefunction collapse. Instead of the wavefunction collapsing into a single state upon measurement, MWI posits that all possible outcomes of the measurement occur in some world.

Quantum Decoherence

Quantum decoherence is a key concept in the Many-Worlds Interpretation. It is the process by which a quantum system interacting with its environment loses its quantum behavior, appearing to "collapse" into a single state. In MWI, decoherence is the mechanism by which the world appears to "split" into many worlds. Each world corresponds to a different possible outcome of a quantum measurement, and each world is as real as the others.

Criticisms and Controversies

Despite its intriguing implications, the Many-Worlds Interpretation has been the subject of much debate and criticism. Some physicists argue that it is untestable and therefore unscientific. Others take issue with the idea of a literal infinity of worlds, arguing that it is extravagant or even absurd. Still others argue that MWI fails to solve the measurement problem, a central issue in the interpretation of quantum mechanics.

Implications for Quantum Computing

The Many-Worlds Interpretation has significant implications for quantum computing. In a quantum computer, computations are carried out in superposition states, with each state representing a possible outcome of the computation. According to MWI, each of these outcomes is realized in some world, potentially allowing for massively parallel computation.