Predating even the Natural Hand Accord, the Quantum Moratorium was an international agreement (or, rather, supercorporate agreement) early in the Era of Communication. It stated quite simply that any research or development on quantum computing exceeding 3-qubit, 8-dimensional vector machines ran contrary to the interest of international commerce and security. Absolon Universal and Solaton Systems, indisputably the two most powerful and technologically capable information-focused supercorporations on the planet, tendered the agreement, and their prominent position in their host governments eliminated almost all dissent.
Of course, the running assumption has been that Absolon and Solaton already possessed, and in fact continue to produce and research, extremely powerful quantum computers, and that the agreement was more to prevent unexpected competition or allow business interests to distract from state-centric cryptography work. As a result, almost all encryption on Arcatia is lattice-based, a precaution nearly every government and supercorporation has proven willing to take against theoretical Absolon or Solaton omniscience.
The Pax Equilibrium has never acknowledged the agreement as legitimate, but since it and all of its hosted supercorporations use Absolon processing equipment this is an ultimately meaningless protest. The Great Unity of Progress was slow to sign on, but after doing so made a rather dramatic show of destroying several quantum computing facilities it apparently possessed or had been constructing. Parts relevant to quantum computing have been seized in Jah and Rastakgan for centuries, though few assembled devices are found, and of those the largest was a 128-qubit machine better described as a proof of concept than actual quantum computer. The one great exception to this pattern was during the War, when Unity forces uncovered a massive array of quantum computers in a heavily fortified complex. Interestingly, though the facility was completed several years prior to the outbreak of the war, there was no evidence indicating it was ever properly calibrated, yet alone used. That such a monstrously powerful intelligence/counterintelligence asset would go unused in so desperate a conflict is but one of many disturbing and unanswered questions raised by the war.