Quantum Gate Implementations on Qiskit
18 November 2022
Single Input Gates
There are six different single-input gates whose are: X, Y, Z, S, T and Hadamard gates. X, Y and Z gate rotates Bloch sphere on their named axis by $\pi$ radians. Therefore, they may be called as a bit flip gate for X gate, and phase flip gate for Z gate.
X Gate (NOT Gate for classical states)
Input: $|0\rangle$
from qiskit import QuantumRegister, QuantumCircuit
from numpy import pi
qreg_q = QuantumRegister(1, 'q')
circuit = QuantumCircuit(qreg_q)
circuit.reset(qreg_q[0])
circuit.x(qreg_q[0])
Input: $|-\rangle$
from qiskit import QuantumRegister, QuantumCircuit
from numpy import pi
qreg_q = QuantumRegister(1, 'q')
circuit = QuantumCircuit(qreg_q)
circuit.reset(qreg_q[0])
circuit.x(qreg_q[0])
circuit.h(qreg_q[0])
circuit.x(qreg_q[0])
Multiple Input Gates
There may be many multiple input gates out there, however, what we'll cover in this post is CNOT gate, Bell's states, Toffoli gate and Swap gate.
Bell's States
Bell introduces a standard way to represent quantum entanglement.
Input: $|00\rangle$
from qiskit import QuantumRegister, QuantumCircuit
from numpy import pi
qreg_q = QuantumRegister(2, 'q')
circuit = QuantumCircuit(qreg_q)
circuit.reset(qreg_q[0])
circuit.reset(qreg_q[1])
circuit.barrier(qreg_q[0], qreg_q[1])
circuit.h(qreg_q[0])
circuit.barrier(qreg_q[0], qreg_q[1])
circuit.cx(qreg_q[0], qreg_q[1])
Input: $|01\rangle$
from qiskit import QuantumRegister, QuantumCircuit
from numpy import pi
qreg_q = QuantumRegister(2, 'q')
circuit = QuantumCircuit(qreg_q)
circuit.reset(qreg_q[0])
circuit.reset(qreg_q[1])
circuit.x(qreg_q[1])
circuit.barrier(qreg_q[0], qreg_q[1])
circuit.h(qreg_q[0])
circuit.barrier(qreg_q[0], qreg_q[1])
circuit.cx(qreg_q[0], qreg_q[1])
Input: $|10\rangle$
from qiskit import QuantumRegister, QuantumCircuit
from numpy import pi
qreg_q = QuantumRegister(2, 'q')
circuit = QuantumCircuit(qreg_q)
circuit.reset(qreg_q[0])
circuit.reset(qreg_q[1])
circuit.x(qreg_q[0])
circuit.barrier(qreg_q[0], qreg_q[1])
circuit.h(qreg_q[0])
circuit.barrier(qreg_q[0], qreg_q[1])
circuit.cx(qreg_q[0], qreg_q[1])
Input: $|11\rangle$
from qiskit import QuantumRegister, QuantumCircuit
from numpy import pi
qreg_q = QuantumRegister(2, 'q')
circuit = QuantumCircuit(qreg_q)
circuit.reset(qreg_q[0])
circuit.reset(qreg_q[1])
circuit.x(qreg_q[0])
circuit.x(qreg_q[1])
circuit.barrier(qreg_q[0], qreg_q[1])
circuit.h(qreg_q[0])
circuit.barrier(qreg_q[0], qreg_q[1])
circuit.cx(qreg_q[0], qreg_q[1])