QFT

from qiskit import QuantumRegister, ClassicalRegister, QuantumCircuit
 
qr1 = QuantumRegister(2)
qr2 = QuantumRegister(1)
cr1 = ClassicalRegister(2)
cr2 = ClassicalRegister(1)
qc = QuantumCircuit(qr1, qr2, cr1, cr2)
 
print("List the qubits in this circuit:", qc.qubits)
print("List the classical bits in this circuit:", qc.clbits)

List the qubits in this circuit: [Qubit(QuantumRegister(2, 'q0'), 0),
Qubit(QuantumRegister(2, 'q0'), 1), Qubit(QuantumRegister(1, 'q1'), 0)]
List the classical bits in this circuit: [Clbit(ClassicalRegister(2, 'c0'), 0),
Clbit(ClassicalRegister(2, 'c0'), 1), Clbit(ClassicalRegister(1, 'c1'), 0)]

from qiskit import QuantumCircuit
 
circuit = QuantumCircuit(2)
circuit.h(0)
circuit.cx(0, 1)
print(circuit.global_phase)

0.0

from numpy import pi
 
circuit.global_phase = pi/4
print(circuit.global_phase)

0.7853981633974483

from qiskit import QuantumCircuit
from qiskit.providers.fake_provider import GenericBackendV2
from qiskit.transpiler import generate_preset_pass_manager
 
# Create circuit to test transpiler on
qc = QuantumCircuit(3, 3)
qc.h(0)
qc.cx(0, 1)
qc.swap(1, 2)
qc.cx(0, 1)
 
# Add measurements to the circuit
qc.measure([0, 1, 2], [0, 1, 2])
 
# Specify the QPU to target
backend = GenericBackendV2(3)
 
# Transpile the circuit
pass_manager = generate_preset_pass_manager(
optimization_level=1, backend=backend
)
transpiled = pass_manager.run(qc)
 
# Print the layout after transpilation
print(transpiled.layout.routing_permutation())

[0, 1, 2]

from qiskit import QuantumCircuit
 
qc = QuantumCircuit(2, 2, metadata={'experiment_type': 'Bell state experiment'})
 
print(qc.metadata)

{'experiment_type': 'Bell state experiment'}

from qiskit import QuantumCircuit, QuantumRegister, AncillaRegister
 
# Create a 2-qubit quantum circuit
reg = QuantumRegister(2)
qc = QuantumCircuit(reg)
 
# Create an ancilla register with 1 qubit
anc = AncillaRegister(1)
qc.add_register(anc)  # Add the ancilla register to the circuit
 
print("Number of ancilla qubits:", qc.num_ancillas)

Number of ancilla qubits: 1

from qiskit import QuantumCircuit
 
# Create a new circuit with two qubits and one classical bit
qc = QuantumCircuit(2, 1)
print("Number of classical bits:", qc.num_clbits)

Number of classical bits: 1

from qiskit import QuantumCircuit
from qiskit.providers.fake_provider import GenericBackendV2
from qiskit.transpiler import generate_preset_pass_manager
 
qc = QuantumCircuit(2)
qc.h(0)
qc.cx(0, 1)
qc.measure_all()
 
# Print the original circuit
print("Original circuit:")
print(qc)
 
# Transpile the circuit with a specific basis gates list and print the resulting circuit
backend = GenericBackendV2(2, basis_gates=['u1', 'u2', 'u3', 'cx'])
pm = generate_preset_pass_manager(
    optimization_level=1, backend=backend, scheduling_method="alap"
)
transpiled_qc = pm.run(qc)
print("Transpiled circuit with basis gates ['u1', 'u2', 'u3', 'cx']:")
print(transpiled_qc)
 
# Print the start times of each instruction in the transpiled circuit
print("Start times of instructions in the transpiled circuit:")
for instruction, start_time in zip(transpiled_qc.data, transpiled_qc.op_start_times):
    print(f"{instruction.operation.name}: {start_time}")

Original circuit:
        ┌───┐      ░ ┌─┐
q_0: ┤ H ├──■───░─┤M├───
        └───┘┌─┴─┐ ░ └╥┘┌─┐
q_1: ─────┤ X ├─░──╫─┤M├
            └───┘ ░  ║ └╥┘
meas: 2/══════════════╩══╩═
                    0  1

Transpiled circuit with basis gates ['u1', 'u2', 'u3', 'cx']:
            ┌─────────┐          ░ ┌─────────────────┐┌─┐
q_0 -> 0 ───┤ U2(0,π) ├──────■───░─┤ Delay(1255[dt]) ├┤M├
        ┌──┴─────────┴───┐┌─┴─┐ ░ └───────┬─┬───────┘└╥┘
q_1 -> 1 ┤ Delay(196[dt]) ├┤ X ├─░─────────┤M├─────────╫─
        └────────────────┘└───┘ ░         └╥┘         ║
meas: 2/═══════════════════════════════════╩══════════╩═
                                            1          0

Start times of instructions in the transpiled circuit:
u2: 0
delay: 0
cx: 196
barrier: 2098
delay: 2098
measure: 3353
measure: 2098

>>> from qiskit.circuit import QuantumCircuit, Parameter
>>> a, b, elephant = Parameter("a"), Parameter("b"), Parameter("elephant")
>>> circuit = QuantumCircuit(1)
>>> circuit.rx(b, 0)
>>> circuit.rz(elephant, 0)
>>> circuit.ry(a, 0)
>>> circuit.parameters  # sorted alphabetically!
ParameterView([Parameter(a), Parameter(b), Parameter(elephant)])

>>> from qiskit.circuit import QuantumCircuit, Parameter
>>> angles = [Parameter("angle_1"), Parameter("angle_2"), Parameter("angle_10")]
>>> circuit = QuantumCircuit(1)
>>> circuit.u(*angles, 0)
>>> circuit.draw()
   ┌─────────────────────────────┐
q: ┤ U(angle_1,angle_2,angle_10) ├
   └─────────────────────────────┘
>>> circuit.parameters
ParameterView([Parameter(angle_1), Parameter(angle_10), Parameter(angle_2)])

>>> from qiskit.circuit import QuantumCircuit, Parameter, ParameterVector
>>> x = ParameterVector("x", 12)
>>> circuit = QuantumCircuit(1)
>>> for x_i in x:
...     circuit.rx(x_i, 0)
>>> circuit.parameters
ParameterView([
    ParameterVectorElement(x[0]), ParameterVectorElement(x[1]),
    ParameterVectorElement(x[2]), ParameterVectorElement(x[3]),
    ..., ParameterVectorElement(x[11])
])

from qiskit import QuantumCircuit
 
qc = QuantumCircuit(2, 2, name="my_circuit")
print(qc.name)

my_circuit