new_contents: """
  Build the quantum fourier transform (qft) for a desire
  number of quantum bits using Qiskit framework. This
  experiment run in IBM Q simulator with 10000 shots.
  This circuit can be use as a building block to design
  the Shor's algorithm in quantum computing. As well as,
  quantum phase estimation among others.
  .
  References:
  https://en.wikipedia.org/wiki/Quantum_Fourier_transform
  https://qiskit.org/textbook/ch-algorithms/quantum-fourier-transform.html
  """
  
  import math
  
  import numpy as np
  import qiskit
  from qiskit import Aer, ClassicalRegister, QuantumCircuit, QuantumRegister, execute
  
  
  def quantum_fourier_transform(number_of_qubits: int = 3) -> qiskit.result.counts.Counts:
      """
      # >>> quantum_fourier_transform(2)
      # {'00': 2500, '01': 2500, '11': 2500, '10': 2500}
      # quantum circuit for number_of_qubits = 3:
                                                 ┌───┐
      qr_0: ──────■──────────────────────■───────┤ H ├─X─
                  │                ┌───┐ │P(π/2) └───┘ │
      qr_1: ──────┼────────■───────┤ H ├─■─────────────┼─
            ┌───┐ │P(π/4)  │P(π/2) └───┘               │
      qr_2: ┤ H ├─■────────■───────────────────────────X─
            └───┘
      cr: 3/═════════════════════════════════════════════
      Args:
          n : number of qubits
      Returns:
          qiskit.result.counts.Counts: distribute counts.
  
      >>> quantum_fourier_transform(2)
      {'00': 2500, '01': 2500, '10': 2500, '11': 2500}
      >>> quantum_fourier_transform(-1)
      Traceback (most recent call last):
          ...
      ValueError: number of qubits must be > 0.
      >>> quantum_fourier_transform('a')
      Traceback (most recent call last):
          ...
      TypeError: number of qubits must be a integer.
      >>> quantum_fourier_transform(100)
      Traceback (most recent call last):
          ...
      ValueError: number of qubits too large to simulate(>10).
      >>> quantum_fourier_transform(0.5)
      Traceback (most recent call last):
          ...
      ValueError: number of qubits must be exact integer.
      """
      if type(number_of_qubits) == str:
          raise TypeError("number of qubits must be a integer.")
      if not number_of_qubits > 0:
          raise ValueError("number of qubits must be > 0.")
      if math.floor(number_of_qubits) != number_of_qubits:
          raise ValueError("number of qubits must be exact integer.")
      if number_of_qubits > 10:
          raise ValueError("number of qubits too large to simulate(>10).")
  
      qr = QuantumRegister(number_of_qubits, "qr")
      cr = ClassicalRegister(number_of_qubits, "cr")
  
      quantum_circuit = QuantumCircuit(qr, cr)
  
      counter = number_of_qubits
  
      for i in range(counter):
  
          quantum_circuit.h(number_of_qubits - i - 1)
          counter -= 1
          for j in range(counter):
              quantum_circuit.cp(np.pi / 2 ** (counter - j), j, counter)
  
      for k in range(number_of_qubits // 2):
          quantum_circuit.swap(k, number_of_qubits - k - 1)
  
      # measure all the qubits
      quantum_circuit.measure(qr, cr)
      # simulate with 10000 shots
      backend = Aer.get_backend("qasm_simulator")
      job = execute(quantum_circuit, backend, shots=10000)
  
      return job.result().get_counts(quantum_circuit)
  
  
  if __name__ == "__main__":
      print(
          f"Total count for quantum fourier transform state is: \
      {quantum_fourier_transform(3)}"
      )
  
subject: create quantum_fourier_transform (#6682)