Technical Definition
Consider a full Von Neumann measurement by giving a quantum description to both the system and the measuring apparatus . Suppose the dynamics can be described by a Hamiltonian of the form
where Hself is the self-interaction of the system and Hint is the coupling between the system and the measuring apparatus. Generally, the Hint term is modeled as "turning on" for only a brief time and yielding the ideal (weak) Von Neumann measurement:
This measurement is a QND measurement if
Read more about this topic: Quantum Nondemolition Measurement
Famous quotes containing the words technical and/or definition:
“The axioms of physics translate the laws of ethics. Thus, “the whole is greater than its part;” “reaction is equal to action;” “the smallest weight may be made to lift the greatest, the difference of weight being compensated by time;” and many the like propositions, which have an ethical as well as physical sense. These propositions have a much more extensive and universal sense when applied to human life, than when confined to technical use.”
—Ralph Waldo Emerson (1803–1882)
“Although there is no universal agreement as to a definition of life, its biological manifestations are generally considered to be organization, metabolism, growth, irritability, adaptation, and reproduction.”
—The Columbia Encyclopedia, Fifth Edition, the first sentence of the article on “life” (based on wording in the First Edition, 1935)