We propose a method for constructing n bit quantum gate (Λ n-1 (W) gate) by using basic 2 bit quantum gates,which is based on Barencos work.This scheme is easier to construct and to implement.
We present a general method to construct quantum logic gates using one-bit``teleportation'' as a basic primitive, extending previous results based ontraditional two-bit teleportation (D. Gottesman and I. L. Chuang, Nature {\\bf402}, 390, 1999). This allows the realization of a variety of useful quantumoperations that cannot be directly performed due to some physical constraints.In particular, this technique leads to straightforward and systematicconstruction of many fault-tolerant encoded operations, including the pi/8and Toffoli gates, and remote quantum operations.
General n-qubit controlled unitary gates are frequently used in quantum information processing tasks. Barenco, Bennett, Cleve, Di Vincenzo, Margolus and Shor [Phys. Rev. A52 (1995) 3457] have given the general construction methods, and explicit results for up-to-four-qubits controlled unitary gates. We extended their calculation and gave two analytic expressions for the construction of general n-qubit controlled unitary gates in terms of one-qubit and two-qubit CNOT gates. There are two expressions – one is exponential in the qubit number which is efficient for up to ten qubits, and the other is polynomial in the qubit number, which is efficient for more than ten qubits.
We present numerical results which show how two-bit logic gates can be used in the design of a quantum computer. We show that the Toffoli gate, which is a universal gate for all classical reversible computation, can be implemented using a particular sequence of exactly five two-bit gates. An arbitrary three-bit unitary gate, which can be used to build up any arbitrary quantum computation, can be implemented exactly with six two-bit gates. The ease of implementation of any particular quantum operation is dependent upon a very non-classical feature of the operation, its exact quantum phase factor.
We present numerical results which show how two-bit logic gates can be used in the design of a quantum computer. We show that the Toffoli gate, which is the universal gate for all classical reversible computation, can be implemented using a particular sequence of exactly five two-bit gates. An arbitrary three-bit unitary gate, which can be used to build up any arbitrary quantum computation, can be implemented exactly with six two-bit gates. The ease of implementation of any particular quantum operation is dependent upon a very nonclassical feature of the operation, its exact quantum phase factor.>