At the quantum level, merely measuring something affects it. You may have heard it said that you can know the location, but not the velocity, or the velocity but not the location?
See my tag line and look it up. It is all probabilities until a measurement is made.
I guess I am too old for the smoke and mirrors method of science. I prefer physics to metaphysics.
This is well known as Heisenberg Uncertainty Principle aka Uncertainty Principle or Heisenberg Effect, or in layman's terms, object under observation changes its behaviour or state and is therefore unmeasurable, or as stated by Werner Heisenberg, "The more precisely the position is determined, the less precisely the momentum is known in this instant, and vice versa."
They key exchange is a slight variation of or not that much different from PGP (Pretty Good Privacy) public-private/symmetric keys mechanism, developed and published by Phil Zimmermann in the early 1990s, except in this case it's fortified by the use of quantum mechanics to make even the key exchange impossible to tap without breaking communication.
Nothing here is revolutionary, the idea of the practical and inexpensive secure quantum net communications using fiber optics (or even "fixed wireless" lasers) has been around for more than 15 years. The scalability has been tested and established when Abilene Project gave way to Internet2 in 2007.