3.2. Quantum gates
Quantum gates are unitary operators (
) working on one, two, or three qubits. The norm is preserved when applied to a quantum state. The action of a quantum gate on a quantum state corresponds to the multiplication of the matrix representing the gate by the vector representing the quantum state: 
.
In this section, a tensor product of 
qubits is represented with the first qubit on the left-most side of the tensor product: 
where 
. Please note that we are not using the Qiskit tensor ordering of qubits unless specifically specified.
In this section, we cover the following:
- Section 3.2.1, Single-qubit quantum gates
- Section 3.2.2, Two-qubit quantum gates
- Section 3.2.3, Three-qubit quantum gates
- Section 3.2.4, Serial wired gates and parallel quantum gates
- Section 3.2.5, Creation of a Bell state
- Section 3.2.6, Parallel Hadamard gates
3.2.1. Single-qubit quantum gates
A single-qubit gate 
has a 
unitary matrix form: 
.
In this...