from qiskit import QuantumCircuit
from qiskit.quantum_info import Statevector
qc = QuantumCircuit(1)
qc.h(0)  # split amplitude equally
qc.z(0)  # introduce a relative minus sign
qc.h(0)  # interfere the two paths
print(qc.draw())
print(Statevector.from_instruction(qc).probabilities_dict())
# Expected: {'1': 1.0}