The Quantum Measurement Problem
There are just so many interpretations of quantum mechanics that attempting to understand it these days seems like a road leading to nowhere. “Shut up and calculate” appears to be the best we can do. Is that satisfying? Well, nobody likes it, that’s for sure.
So what is the quantum measurement problem exactly? There are multiple formulations, most of them mathematical, some more funny, like “is the moon there when you don’t look at it”. I personally suggest the following, which needs no math and explains the underlying issue quite well.
If someone measures the location of a particle, like a photon, quantum mechanics predicts that the probability to find it in some arbitrary remote location, like the dark side of the moon, is strictly speaking not zero. Mathematically, there is nothing absurd to it: the probability is represented by a “wave-function”, and that function in many cases reaches zero only asymptotically, which is a way to say it never quite makes it to zero.
But physically, there is something a little suspect about this statement. Imagine that, to locate my photon, I use a detector, like an old fashioned photographic plate. So every location on the plate tells me where the photon was when it hit the plate. That’s based on me knowing where the plate was to start with.
Now tell me, how does that plate even tell me that the photon was on the moon? What point of the plate exactly corresponds to this “on the moon” location?
Incomplete Measurements?
Saturday, November 18, 2006