Understanding Decoherence in Everettian Quantum Theory

Loss of quantum coherence due to interaction with the environment.

Decoherence is a fundamental concept in the Everettian Quantum Theory, also known as the Many-Worlds Interpretation. This article aims to provide a comprehensive understanding of the role of decoherence in this theory and its relationship with the measurement problem.

Introduction to Decoherence

Decoherence is a process that plays a crucial role in the transition from quantum to classical behavior. It describes how the "quantumness" of a system can effectively disappear, leaving behind a classical system. In the context of the Many-Worlds Interpretation, decoherence is the mechanism that leads to the branching of the universe into multiple, non-interacting worlds.

Role of Decoherence in the Many-Worlds Interpretation

In the Many-Worlds Interpretation, every possible outcome of a quantum measurement happens in some "branch" of the universe. However, these branches do not interact with each other, leading to the question of why we only observe one outcome. The answer lies in the process of decoherence.

When a quantum system interacts with its environment, it becomes entangled with it. This entanglement causes the quantum system to lose its coherence, effectively becoming a classical system. This process is known as decoherence. In the Many-Worlds Interpretation, decoherence is the mechanism that causes the universe to "split" into multiple branches, each representing a different outcome of the quantum measurement.

Decoherence and the Measurement Problem

The measurement problem in quantum mechanics refers to the question of why we only observe one outcome of a quantum measurement, despite the theory predicting multiple possible outcomes. In the Many-Worlds Interpretation, the measurement problem is resolved by the process of decoherence.

When a quantum measurement is made, the system becomes entangled with the measuring device and the environment, leading to decoherence. This causes the wave function of the system to "collapse" into a superposition of states, each corresponding to a different measurement outcome. However, due to decoherence, these states do not interfere with each other, effectively becoming separate "worlds". Therefore, we only observe one outcome because we are only in one of these worlds.

In conclusion, decoherence is a crucial concept in the Everettian Quantum Theory. It is the mechanism that leads to the branching of the universe into multiple, non-interacting worlds, and it provides a solution to the measurement problem in quantum mechanics. Understanding decoherence is essential for a comprehensive understanding of the Many-Worlds Interpretation.