A chef tastes the soup to see how much salt is in the pot. Physicists did something similar with crystals: they aimed X-rays at them and, from how the rays scattered, calculated how 'spread out' the electrons are in chemical bonds.
In diamond, carbon atoms are held together by shared electrons, like two people sharing one blanket. In lithium fluoride, the bond is different: one atom gives an electron to the other, and they attract each other like opposite charges. It turns out that in diamond, the electron blanket is wider and thinner than in lithium fluoride. This means that in a covalent bond, electrons are more delocalized: they are 'spread out' over a larger volume.
The measurements gave concrete numbers: the quantum weight of diamond turned out to be larger than that of lithium fluoride. Quantum weight shows how much quantum information 'flows' along the bond. A larger weight means more delocalization, a larger total 'area' of the electron blanket.
This method is like an X-ray machine for the invisible world of electrons. Now we can compare different materials and better understand why some bonds are stronger and others conduct electricity. And this is just the beginning: the same approach can be applied to superconductors and other unusual materials.
Diamond is one of the hardest materials, yet its electrons are more 'spread out' than in brittle lithium fluoride. Strength and delocalization go hand in hand.