Quantum encryption is the expected exponential increase in difficulty when quantum computing is applied to encoding and decoding data.
Quantum computers, while still a way off, are thought to be a threat to the encryption that today’s classical computers use. Because the former are thought to be able to perform the work of the latter in a fraction of the time, scientists are anticipating that nation states and other large, well-resourced adversaries may leverage their power to break encryption. As a response to the threat, markedly more complex quantum encryption would have to arise. The gap between when one competitor in that “crypto arms race” and the other has quantum capability is problematic for the party lacking it, since its adversary might overtake their defenses immediately.
The threat and indeed the conversation are hypothetical. Quantum computing’s power being far higher than any classical supercomputer is still an open question. In addition to quantum encryption’s threat being an unsettled science, quantum computers’ near-infeasible investments and implementation requirements make the quantum encryption war unlikely for perhaps the next decade, and one that will emerge publicly.
"Quantum computing's rise is a decade or more in the future, and limited to entities with the resources to develop and maintain it. Once it moves from the development stage and into production, we'll also see quantum encryption with exponentially more difficulty as a natural component to securing these advanced machines."