A New Problem for Quantum Mechanics

In this article I raise a new problem for quantum mechanics, which call the control problem. Like measurement problem, places fundamental constraint on theories. The characteristic feature of is its focus state preparation. particular, whereas turns premise about completeness (‘no hidden variables’), our ability to prepare or states. After raising discuss some applications. suggest that it provides useful lens through view existing theories interpretations, in part because draws attention aspects those does not (such as role conditional and relative states). also helps clarify physical significance well-known no-go result—the no-cloning theorem—on based.