First-kind measurements, non-demolition measurements, and conservation laws
Abstract
A general discussion is given for first-kind (FK) and quantum non-demolition (QND) measurements. The general conditions for these measurements are derived, including the most general one (called the weak condition), an intermediate one, and the strongest one. The weak condition indicates that we can realize a FK or QND measuring apparatus of wide classes of observables by allowing the apparatus to have a finite response range. A recently-proposed QND photodetector using an electron interferometer is an example of such apparatus.
Turn this paper into a full lesson
ArcXiv compiles a staged curriculum from this paper: 8-12 lessons across beginner → advanced, synthesised section guides, visuals, flashcards, a quiz, exercises, and on-demand deep dives per section. Grounded in the abstract, never invented.