  The primordial model of quantum computation was introduced over thirty years
ago and the first quantum algorithms have appeared for over twenty years. Yet
the exact architectures for quantum computer seem foreign to an undergraduate
student major in computer science or engineering, even though the mass media
has helped popularize the terminologies in the past decade. Despite being a
cutting-edge technology from both the theoretical and the experimental
perspectives, quantum computation is indeed imminent and it would be helpful to
give the undergraduate students at least a skeleton understanding of what a
quantum computer stands for. Since instruction-set architectures originated
from classical computing models are familiar, we propose analogously a set of
quantum instructions, which can be composed to implement renowned quantum
algorithms. Albeit the similarity one can draw between classical and quantum
computer architectures, current quantum instructions are fundamentally
incommensurable from their classical counterparts because they lack the innate
capability to implement logical deductions and recursions. We discuss this
trait in length and illustrate why it is held responsible that current quantum
computers not be considered general computers.
