The quantum gate array is the natural quantum generalization of acyclic combinational logic " circuit " studied in conventional computational complexity theory . in 1995 , barenco showed that almost any two - bit gate is universal , so building a feasible two - bit logic gate is the first step to engineer a quantum computer . in principle , the quantum bit can be carried by any two states system 在眾多的量子計算機模型中目前討論最廣泛的是量子計算機門組網絡模型,量子計算機門組網絡模型是經典計算機門組網絡結構的量子推廣,它是根基于barenco等人所證明的“一個兩比特受控操作和對單比特進行任意操作的門可以構成一個‘通用量子邏輯門組’ ”之上的。
Computational complexity theory is a branch of the theory of computation in theoretical computer science and mathematics that focuses on classifying computational problems according to their inherent difficulty, and relating those classes to each other. A computational problem is understood to be a task that is in principle amenable to being solved by a computer, which is equivalent to stating that the problem may be solved by mechanical application of mathematical steps.