In quantum mechanics, the conservation of information is a fundamental principle that ensures that information is not lost or destroyed during physical processes. However, the concept of information conservation becomes more subtle when it comes to quantum collapse or measurement.
Quantum collapse, also known as wave function collapse or measurement collapse, occurs when a quantum system interacts with a measuring device or an observer, causing the system's wave function to "collapse" into one of its possible states. This collapse process is described by the mathematical formalism of quantum mechanics, particularly the Born rule, which provides probabilities for different measurement outcomes.
At the heart of the issue is the question of what happens to the information encoded in the superposition of states prior to collapse. According to the traditional interpretation of quantum mechanics, often referred to as the Copenhagen interpretation, the wave function represents a probability distribution, and the collapse occurs when an observer makes a measurement and "chooses" one of the possible outcomes. In this view, the information encoded in the superposition is effectively discarded, and only the measurement outcome is retained.
However, other interpretations of quantum mechanics, such as the many-worlds interpretation or the consistent histories approach, provide different perspectives on the conservation of information during quantum collapse. In these interpretations, the wave function evolution is considered to be deterministic and unitary, meaning that it preserves information. According to these views, when a measurement is made, the observer becomes entangled with the measured system, and the entire system, including the observer, evolves into a superposition of different outcomes. Each outcome corresponds to a different branch or history of the universe, and all possibilities are accounted for. From this perspective, information is not lost during the collapse process but rather becomes entangled with the observer and the environment.
It is important to note that the exact nature of quantum collapse and the conservation of information are still subjects of ongoing scientific and philosophical debate. Different interpretations offer different explanations and understandings of these phenomena. While experiments and theoretical developments continue to shed light on these questions, a consensus has not been reached, and the topic remains an active area of research in quantum foundations.