Alice t3

Second CNOT gate completes 1st qubit's entanglement with 2nd and 3rd qubits.


CNOT or Condition NOT is a two qubit operation with the 1st qubit 'control' on 2nd qubit 'target' so that the target's state is negated if the control has state |1>.

In the circuit | four, quattuor, sa > the input to this second CNOT gate is equal probabilities for |100> and |111> state vectors. After CNOT the |100> state vector has been replaced by the |110> state vector and |111> has been replaced by |101>, i.e. |100>,|111> -> |110>,|101>.

The second CNOT gate has no effect on the state vectors in circuit | zero, hihil, yeong > since the control qubit is in state |0> for each of the possible input state vectors |000> and |011>.