It's only a matter of time.
It's taken about sixty years to scale lasers from continuous milliwatts to continuous megawatts.
But it only took forty years to scale semiconductor memory from a few hundred bits to gigabytes.
The technology for producing and storing antimatter exists today, at least for a few thousand particles at a time. Eventually, it will be scaled up. I hope it's done far out in space, but it may not be.
Even if, by mass production, that you get only 80% of the theoretical performance, you’d still be looking at a substance with 400% better performance than diamond.
I can imagine covering cement with this and having a cement structure that would last 1000 years before it would be so well protected against the elements.
Space elevator.