International Association of Scientific Innovation and Research (IASIR)
An important feature of quantum computing is reversibility, because evolution of a quantum system is described by a unitary operator and hence it is reversible. Quantum cost is another important factor of any reversible circuit. The lowest quantum cost indicates the lowest price of reversible circuit. By lowest quantum cost can make a quantum computer. In this paper, the authors show how to find the lowest quantum cost and show an advanced Toffoli gate that contains lowest quantum cost.