The SWAP logic gate

There is an important relation between the two CNOT gates, of a two-qubit system, which is CNOTfl = H CNOT, H H (see [1]). 

In classical computation, any logical operation can be done from combinations of the logic gate nand (NOT-AND). The similar is true in quantum computing any quantum operation can be implemented using a set of universal logic gates. Such a set is composed of the Hadamard (H), controlled NOT (CNOT), phase (S) and jr/8 (T). 

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