Added Qiskit Trotter circuit gen benchmark

    H = H - Jz * (Z(i) * Z(i + 1))

  return H

n_qubits = [10, 20, 50, 100]

n_qubits = [5, 10, 20, 50, 100]

nbSteps = 100

for nbQubits in n_qubits:

from qiskit.aqua.operators import (X, Y, Z, I, CX, H, ListOp, CircuitOp, Zero, EvolutionFactory,

                                   EvolvedOp, PauliTrotterEvolution, QDrift, Trotter, Suzuki)

from qiskit import QuantumRegister, ClassicalRegister, QuantumCircuit

import time

def X_op(idxs, n_qubits):

  op = None

  if 0 in idxs:

    op = X

  else:

    op = I

  for i in range(1, n_qubits):

    if (i in idxs):

      op ^= X

    else:

      op ^= I

  return op

def Z_op(idxs, n_qubits):

  op = None

  if 0 in idxs:

    op = Z

  else:

    op = I

  for i in range(1, n_qubits):

    if (i in idxs):

      op ^= Z

    else:

      op ^= I

  return op

def heisenberg_ham(n_qubits):

  Jz = 1.0

  h = 1.0

  H = -h * X_op([0], n_qubits)

  for i in range(1, n_qubits):

    H = H - h * X_op([i], n_qubits)

  for i in range(n_qubits - 1):

    H = H - Jz * (Z_op([i, i + 1], n_qubits))

  return H

n_qubits = [10, 20, 50, 100]

nbSteps = 100

def trotter_circ(q, exp_args, n_steps):

  qc = QuantumCircuit(q)

  for i in range(n_steps):

    for sub_op in exp_args:

      qc += PauliTrotterEvolution().convert(EvolvedOp(sub_op)).to_circuit()

  return qc

n_qubits = [5, 10, 20, 50, 100]

nbSteps = 100

for nbQubits in n_qubits:

  ham_op = heisenberg_ham(nbQubits)

  q = QuantumRegister(nbQubits, 'q')

  start = time.time()

  comp = trotter_circ(q, ham_op.oplist, nbSteps)

  end = time.time()

  print("n instructions =", comp.depth(), "; Kernel eval time:", end - start, " [secs]")