On Wednesday, November 15, 2017 at 7:54:27 PM UTC-7, Brent wrote: > > Interesting questions. Whenever we talk about a system being in a quantum > state, we're thinking of the "system" as some degrees of freedom that are > isolated, so they are not interacting with and becoming entangled with > other things. An SG experiment typically uses silver atoms and refers to > their state as UP or DOWN or LEFT or RIGHT. But that's not a complete > description of the silver atom. It has other degrees of freedom, which we > ignore as irrelevant to the SG measurement. So a "system" which we > describe as having a state, isn't necessarily the same as an object, like a > baseball or even an atom. A classical object like a baseball has lots of > degrees of freedom and they are interacting with the environment, so they > are entangled with states of the environment. Only certain collective > variables, e.g. the conserved ones like momentum, are stable in the stat > mech sense. These ones that are stable against interaction with the > environment are the einselected values we can measure classically. So we > could write a wave-function for the baseball as if it were an isolated > particle, like the silver atom, and ignore all the internal dof which are > not in any definite state because they're entangled with atmospheric > molecules and IR photons, etc. > > Whether something is in a superposition of states isn't an interesting > question because the answer is always "Yes...relative to some basis." The > interesting point is that since constituents in the baseball have > interacted with and are now entangled with air molecules, those > constituents of the baseball are not in any definite state. Only the > constituent PLUS the molecules it is entangled with has a definite state. > In any basis we can imagine measuring, they will be in a superposition > relative to that basis. But in theory there would some basis in which the > isolated baseball plus molecules would be an eigenstate; it's just so > complicated we could never measure in that basis. But if were to consider > a very simple system, like a few electrons then we might be able to measure > in the eigenbasis. > > Brent >
TY. That was very informative. Let's go on. How does a micro constituent of a macro object get entangled with, say, an air molecule? When I think of entanglement, I think of some special process to it.create it. How does it happen spontaneously? Is it stable or does it decay rapidly, and if so into what? TIA. > > On 11/15/2017 5:56 PM, [email protected] <javascript:> wrote: > > Consider a baseball. Is it in some kind of composite state, however > defined, of its constituents? Are all its constituents entangled with the > environment? If some are not, are they in a superposition of states? I pose > these questions because in my discussions with Clark on another thread, > it's unclear what state, if any, a macro object is in, assuming that state > fluctuates. TIA. > -- > 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 [email protected] <javascript:>. > To post to this group, send email to [email protected] > <javascript:>. > Visit this group at https://groups.google.com/group/everything-list. > For more options, visit https://groups.google.com/d/optout. > > > -- 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 [email protected]. To post to this group, send email to [email protected]. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
