Why decoherence solves the measurement problem

Abstract

Although the solution, within standard quantum physics, of the problem of outcomes has been published several times, many authors continue to treat measurement as an unsolved fundamental dilemma. The solution lies in the formation of entangled subsystems, the non-local nature of the measurement state, and the resulting distinction between mixed-state local outcomes and the pure-state global outcome. Upon "measurement" (i.e. entanglement), the quantum system and its measurement apparatus both decohere and collapse into local mixed states while the unitarily-evolving global state remains coherent and un-collapsed. The states we observe are the local, collapsed states. Considerable experimental evidence supports this conclusion. Theoretical objections to this conclusion are rebutted, and a new perspective on measurement and entanglement is noted.