Yes I had meant the QM system to refer to the free electron in my example and the detector as something that interacts with it and changes its state, destroying the previous wavefunction of the free electron. I tend to think of the de Broglie matter waves as physical and only their interactions as quantised. This makes sense of the double slit experiment for me and also what I know of atomic and molecular structure and processes. The wavefunction is - being a "function" - a mathematical description of the physical thing. I do not pretend this is rigorous but it seems to account for what I need to understand. I agree one gets into problems with QM, as with many models, if one pushes it too far beyond what it was designed to do. But then I have an image of the relationship between science and physical reality as a bit like Russian dolls - there is always another one somewhere inside, such that one never gets quite to the final absolute and complete reality. But to me this notion of some that the presence or absence of consciousness alters physical reality is a ludicrously anthropocentric way to view the world. After all, what is consciousness but a neural network in operation, itself made up of biochemical reactions? Defining it is arbitrary.