Fig. 3.

Hardware architectures for quantum computers. We show the architecture of a hybrid classical/quantum computer for quantum chemistry-type calculations. Shown are (A) a serial architecture using a single rotation factory and (B) a parallel architecture with multiple rotation factories. The quantum computer acts as an accelerator to the classical supercomputer. It consists of a classical control front end, a main quantum processor, and a number of auxiliary processing units. The devices labeled QRot build single-qubit rotations using $\pi /8$ rotations created in the T-gate factories labeled Tfac. Red arrows denote quantum communication, and blue arrows represent classical communication.