The Convergence Wall
Finance often asks for an average over possible futures. Classical Monte Carlo is the workhorse for that job, but its error falls only as \(1/\sqrt{N}\). One more decimal digit of accuracy therefore needs roughly 100 times as many samples.
Unit 5 keeps the option price classical. Its quantum circuit reads a compiled phase for the fraction of eight uniformly weighted price bins above the strike, exposing the amplitude-estimation mechanism after state preparation and oracle construction have been supplied.