h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Just wondering what opinions people have about the measurement problem and the associated interpretations of Quantum Mechanics. With a bit of luck my masters project will be looking into the interaction between the measuring device and the system. With a bit of luck I will be able to show that the collapse is due to the interaction.

For people who a confused
The measurement problem is that when a quantum system is observed it collapses into one of the possible states (before the measurement it was in all possible states). This does not happen in a time reversible way unlike the Schroedinger equation which is time reversible.

Prior to measurement/observation there is no way of knowing how many states the system is in, be it one or many. The measuring device is a physical system. If interacting with a physical system "collapses the states" they would be permanently collapsed. The only thing we *know* changes when a measurement is made is our knowledge.

No necessarily permanently collapsed there could be things required for the collapse, for example it needing to be thermodynamically irreversible, i.e. Causes a net increase in Entropy.

Or, since nobody has observed a system with multiple states (on account of this being a postulated property of *un*observed systems, used for purposes of calculation), maybe there is no collapse.

Noggin

You can tell that a system is in two states though, the classical example being the double slit interference patterns. This would not be obtained if it was just in one of the states (but we didn't know which).

"you can tell" = "used for the purposes of calculation"

Hi Arnie. Long time no see.


I can't tell. Looks to me like one very complicated state.

Noggin

Hi Nog, good to hear from you too. I believe that (in the parlance of our times) it's an "entangled" state.

I believe that the real problem isn't just that the probabilities collapse, but that the act of measuring has an effect on the resulting state when it does.

By that, I mean you cannot measure say temperature without affecting the temperature of the object measured. This is, of course, because the 'probe' that you use to capture the measurement generally has to enter the environment, or the object, and is unlikely to be in thermodynamic equillibrium with it.
So, as the probe measures, it also slightly cools or warms depending on the delta.

The same goes for motion measurements. Without knowing in advance what the location, vector, and speed are, one is invariably going to change it in the act of measuring.

motorist:- I'm sorry officer i have no idea how fast i was going, but i did know exactly where i was!!!!!

I don't know where I'm going, but I'm making terrific time!