I was taught the ‘wave (eigenstate) collapse upon measurement’ concept, and in the lab, it’s just silly; the decoherence concept you describe is quite obviously

I was taught the ‘wave (eigenstate) collapse upon measurement’ concept, and in the lab, it’s just silly; the decoherence concept you describe is quite obviously the proper way to think about it, or we wouldn’t have to worry about losses from anything that wasn’t measured. Simple explanation of QM: a classical object has a vector of properties, but in quantum this is a matrix. Any interaction is a matrix multiplication. After a bunch of matrix multiplications, you end up with a single eigenvalue, and now the quantum property matrix acts just like the classical property vector. The choice of linear operators, and probably the internal linearity among properties as well, is just a simplification, but otherwise we’d be mathematically lost in a world of functions that arbitrarily modify other functions.