Constructing the Bell State A common application of the CNOT gate is to maximally entangle two qubits into the Bell state; this forms part of the setup of the superdense coding, quantum teleportation, and entangled quantum cryptography algorithms. To construct , the inputs A (control) and B (target) to the CNOT gate are: and After applying CNOT, the resulting Bell State has the property that the individual qubits can be measured using any basis and will always present a 50/50 chance of resolving to each state. In effect, the individual qubits are in an undefined state. The correlation between the two qubits is the complete description of the state of the two qubits; if we both choose the same basis to measure both qubits and compare notes, the measurements will perfectly correlate. When viewed in the computational basis, it appears that qubit A is affecting qubit B. Changing our viewpoint to the Hadamard basis demonstrates that, in a symmetrical way, qubit B is affecting qubit A. The input state can alternately be viewed as: and In the Hadamard view, the control and target qubits have conceptually swapped and qubit A is inverted when qubit B is . The output state after applying the CNOT gate is which can be shown to be exactly the same state as . C-ROT gate The C-ROT gate (controlled Rabi rotation) is equivalent to a C-NOT gate except for a rotation of the nuclear spin around the z axis. Implementations Trapped ion quantum computers: Cirac–Zoller controlled-NOT gate Mølmer–Sørensen gate See also Toffoli gate (controlled-controlled-NOT gate) Notes References External links Michael Westmoreland: "Isolation and information flow in quantum dynamics" - discussion around the Cnot gate Quantum gates Quantum information science