Quantum measurement and algebraic quantum field theories

It is shown that the physics and semantics of quantum measurement provide a natural interpretation of the weak neighborhoods of the states on observable algebras without invoking any idea of a reading error or a measured range. Then the state preparation process in quantum measurement theory is shown to give the normal (or locally normal) states on the observable algebra. Some remarks are made concerning the physical implications of normal states for systems with an infinite number of degrees of freedom, including questions on open and closed algebraic theories.Work supported in part by the U. S. Atomic Energy Commission.