Alas, but it doesn't look like it will be any day soon -- and in fact, I don't have a candidate in mind, among all my adult fantasy novel ideas.
I would say someday I will write a fantasy novel (for any age) that has nothing whatever to do with quantum mechanics, but that's not too likely, and we don't expect it. I wouldn't propose this as a definition that impinges upon other people's work, but from the inside it looks like the difference between my SF and my fantasy novels is that it's perfectly possible for me to write SF that isn't really about quantum mechanics at any scale.
Sigh.
