Googling for some unrelated topic, I stumbled upon Quantum Mechanics in an Evolving Hilbert Space. A lot of the math in this paper is beyond my present level, but some of the more descriptive passages made intuitive sense to me. Based on this, my question is, is the formalism of an evolving Hilbert space a useful tool to describe (and calculate!) delayed choice experiments? And if so, is there a simplified way to apply the basic principle to toy problems with one or two particles, without necessarily mastering the formalism in its entire awful majesty?