How Does a Quantum Computer Actually Calculate?

A quantum computer can represent many possibilities, but a measurement gives you only a limited result. How does it turn that restriction into useful computation? Follow the calculation from a single qubit to a complete four-candidate search. Discover how amplitudes, phase, interference, and entanglement work together, why Grover's algorithm needs more than superposition, and how Shor's algorithm finds factors by extracting a hidden period. Then explore the physical gates, measurements, and error correction needed to make the mathematics survive in real hardware. This is the mechanism behind quantum computing, including the limits that the phrase “trying every answer at once” leaves out.