Path: utzoo!attcan!telly!lethe!torsqnt!news-server.csri.toronto.edu!cs.utexas.edu!usc!julius.cs.uiuc.edu!wuarchive!hsdndev!cmcl2!rutgers!aramis.rutgers.edu!athos.rutgers.edu!nanotech From: landman@eng.sun.com (Howard A. Landman) Newsgroups: sci.nanotech Subject: Re: STM observation of radioactive decay Keywords: scanning tunnelling microscope quantum Zeno effect Message-ID: Date: 21 Dec 90 18:59:34 GMT Sender: nanotech@athos.rutgers.edu Organization: Sun Microsystems, Mt. View, Ca. Lines: 31 Approved: nanotech@aramis.rutgers.edu Followup to sci.physics. I'll summarize back to sci.nanotech if needed. >Patrick Hayes writes: >isn't it true that every time you scan over an atom with the needle, >you have observed it, thus collapsing the wave function >And JoSH comments: >[There are in fact demonstrated physical systems where repeated measurement > can prevent quantum-mechanical transitions. Yes, but these are all systems where the thing being measured interacts with the thing that may change. The so-called "quantum Zeno effect" shouldn't occur when the thing being measured is independent (formally, when the two QM operators commute). This is the same condition that determines whether there is a Heisenberg uncertainty relationship between the two quantities. >However, in the specific case of the STM, > my guess is that the measurement of the state of the nucleus is far > too indirect for it to have that kind of effect. > --JoSH] This is really the question of whether the position of the atom commutes with its quantum state with respect to decay. I believe that the answer is yes. (Anyone in sci.physics care to confirm or deny this?) Therefore, continual measurement of the position of an atom should not have a quantum Zeno effect on its radioactive decay. -- Howard A. Landman landman@eng.sun.com -or- sun!landman