Controlled NOT gate

In computing science, the controlled NOT gate (also C-NOT or CNOT) is a quantum gate that is an essential component in the construction of a quantum computer. It can be used to entangle and disentangle EPR states. Any quantum circuit can be simulated to an arbitrary degree of accuracy using a combination of CNOT gates and single qubit rotations. The CNOT gate is the "quantization" of a classical gate.

The CNOT gate operates on a quantum register consisting of 2 qubits. The CNOT gate flips the second qubit (the target qubit) if and only if the first qubit (the control qubit) is ${\displaystyle |1\rangle }$.

If one allows only ${\displaystyle \{|0\rangle ,|1\rangle \}}$ as input values for both qubits, the TARGET output of the CNOT gate corresponds to the result of a classical XOR gate. Fixing CONTROL as ${\displaystyle |1\rangle }$, the TARGET output of the CNOT gate yields the result of a classical NOT gate.

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