On Friday, May 9, 2025 at 10:40:42 PM UTC-6 Brent Meeker wrote:
On 5/9/2025 7:08 PM, Alan Grayson wrote: *I can see that the measurement spreads due to instrument limitations are usually immensely larger than the much smaller spreads accounted for by the UP, but what causes these much smaller spreads? Is this a quantum effect? AG* Yes. Quantum evolution is unitary, i.e. the state vector just rotates in a complex Hilbert space so that probability is preserved. Consequently the infinitesimal time translation operator is U=1+e6/6t or in common notation 1-i(e/h)H where H=ih6/6t and h is just conversion factor because we measure energy in different units than inverse time. It's not mathematics, but an empirical fact that h is a universal constant. Brent *If one wants to prepare a system in some momentum state to be measured, doesn't this imply a pre-measurement measurement, and the observable to be measured remains in that state on subsequent measurements? If so, how can the unitary operator, which just changes the state of the system's wf, create the quantum spread? TY, AG* -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To view this discussion visit https://groups.google.com/d/msgid/everything-list/5559d001-bf74-4d78-8bb5-8b26cfaa18cfn%40googlegroups.com.
