Dean,
Thank you very much for telling me about your interesting reaction to my essay; I was quite pleased to hear about it! Getting into a true LSU-mindset is not easy, even for physicists who work with Lagrangians every day. So I'm not at all concerned that you're not sold on the LSU ; the goal of my essay was primarily to raise awareness about the NSU/LSU distinction, and it sounds like I may have succeeded (in your case, anyway).
This distinction has been the biggest problem in communicating my research; hardly anyone seems to have separate mental frameworks for LSU vs. NSU. Several times people have told me that one of my (LSU-style) talks made perfect sense at the time, but later, when they think about it on their own, it just seems crazy. After drilling down for the root cause, I finally figured it out: these people were instinctively retreating to an NSU-mindset without realizing it. (And without realizing that they were briefly thinking in an LSU-mindset in the first place.)
On the technical front, the question of what might be considered a correlation-destroying measurement in different contexts is more carefully addressed in my previous essay contest entry. I agree that this issue makes more sense when viewed from a global, LSU perspective; what matters is not merely the beamsplitter, but also what happens to the beams after they pass through.
Also, thanks for the thought about Cooper pairs; I'm building up a for-general-audience-consumption argument concerning covalent bonds that is probably getting at the same point you're making here.
Thanks again; your comment made my day!
Ken
PS: Yes, QED is a great book. In fact, the biggest red flag in this whole research program is that I'm trying to solve a problem that Feynman himself attempted and failed (to come up with a realistic, physical, interpretation of his path-integral mathematics). But I'm getting more and more convinced that there *is* a solution, one that Feynman would have quite liked.