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Quantum DarwinismQuantum darwinism is the name given to a theorem published in 2004 by Harold, Poulin, and Zurek, which attempts to explain how the objective reality we see arises from the quantum mechanical world. During a measurement process, a phenomenon called quantum decoherence takes place: the system tends to evolve into stable states known as "pointer states", which have the properties of a classical mechanical state (for example, possessing a well-defined position.) The theorem showed that indirect measurements could preserve the pointer states by imprinting them into the state of the "environment", which means that the pointer states can constitute an objective reality. The name "quantum darwinism" seems to imply that the process is analogous to Charles Darwin's theory of evolution, which explains the observed features of biological species by the process of natural selection. In fact, the analogy is at best an extremely loose one; quantum states do not mutate, reproduce, or get eliminated in the way biological organisms do, and the observations that the respective theories seek to address -- the existence of distinct biological species and their adaptation to their natural surroundings in Darwin's case, versus the existence of an objective and consistent classical world in the case of "quantum darwinism" -- are rather different. The problem of many observers is rectified by the fact each individual's observation is based on only a tiny part of the environmental imprint. Furthermore because the imprint is robust (stable) another can be made for a new observer without causing interference; making the pointer states the most "fit" to leave "descendants" that have their properties. This process not only creates the state of the system; it advertises it throughout the environment for all to literally see simultaneously and independently. External links
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