https://www.taurushq.com/blog/quantum-doomsday-planning-1-2-doing-your-risk-assessment-and-the-real-cost-of-quantum-attacks/
Experts in complexity theory have a solid understanding of the quantum speedup concept. While certain computational tasks require an exponential number of operations (relative to input size) on a classical computer, some of these problems can be efficiently solved using a quantum computer (that is, in polynomial time). Consequently, a quantum computer can transform a practically unsolvable problem into a solvable one.
But only a small fraction of computationally hard problems are susceptible to such exponential quantum speedup. Specifically, quantum computers offer limited assistance in searching for optimal solutions to constraint-satisfaction problems (see NP-hard problems). Let's repeat: quantum computers are not "exponentially faster" computers that would turn any computation-intensive problem into a swiftly solvable task.
