Governments (we the people in general) have the right and duty to regulate corporations, non-human entities which exist at our regulatory pleasure. The US and the EU could easily rip Google/MS/Apple to pieces if they wanted to. Hit some other media conglomerates while they're at it. Vote or something.
holds pretty generally; there isn't any new math or algorithm here that I can see. Their own complexity analysis (eqns. 7 and 8) shows this performs about the same as using Karatsuba multiplication on the entries of the matrices (instead of on the matrices themselves).
You can easily set up the cards with two honest Players. Player 1 sorts and makes four piles S-C--H-D. Player 1 looks away, Player 2 puts 8/12 markers randomly on either the first two piles or the last two piles, then randomizes the piles (so Player 1 gets no information from the order).
The hard part is how to do the trading with real cards. You would have to structure/limit the trading a lot instead of the free-for-all that seems to be going on.
More mathy: A. Yu. Kitaev, A. H. Shen, M. N. Vyalyi, "Classical and Quantum Computation"
A killer app: Peter Shor, "Polynomial-Time Algorithms for Prime Factorization and Discrete Logarithms on a Quantum Computer"
Some course notes: https://math.mit.edu/~shor/435-LN/