Controlled NOT gate

A controlled NOT gate, or CNOT, is a type of logic gate that looks at two input signals and then produces one output signal. One input signal is called the 'control' signal, and the other is called the 'target' signal. If the control signal is in the 'on' state (usually a 1 or 'high' signal), the output is the opposite of the target signal. In other words, when the control signal is 1, it "flips" the target signal. If the control signal is 0 (or 'low'), the output is the same as the target signal.