Underpinning much of modern technology, from smartphones to scanning tunneling microscopes to particle colliders, there is Fermi's Golden Rule.
Named for 20th century Italian-American physicist Enrico Fermi (but actually discovered by British physicist Paul Dirac), the rule is a formula that connects what can be measured in an experiment - such as how fast atoms "jump" between energy states - to the microscopic properties of a quantum mechanical system. The formula is taught in every undergraduate quantum physics class.
Yet scientists sometimes misapply it. They either misjudge the conditions under which the formula works, or they miss the "window" for its use.
A "user manual" for Fermi's Golden Rule would be a boon to researchers, says Yale physicist Nir Navon - and now he and his lab partners have provided one.
