allow repeating parameters

[hhorii]

Summary

Allow use of a circuit for multiple parameters

Details and comments

Currently, parameterized Qobj allows a circuit to take a parameter set. This PR allows a circuit to take multiple parameter set.

[hhorii]

Just repeating circuits may not satisfy Aqua's use case. Aqua inserts calibration circuits. These inserted circuits should not be repeated.

[chriseclectic]

I think this is already supported, its just nested differently. The code example in #485 shows how to runs multiple parameterizations for multiple circuits (Which need not have the same number of parameterizations).

For the case of a single circuit I want to run with 10 different parameterizations for example I can do:

import numpy as np
from qiskit import *

# Example circuit
qc = QuantumCircuit(1, 1)
qc.ry(0, 0)
qc.rx(0, 0)
qc.measure(0, 0)

# Make random parameter values
num_parameterizations = 10
ry_params = np.random.rand(num_parameterizations)
rx_params = np.random.rand(num_parameterizations)
parameterizations = [
    [[[0, 0], ry_params], [[1, 0], rx_params]]
]

# Assemble parameterized qobj
qobj = assemble(qc, parameterizations=parameterizations)

# Execute
sim = Aer.get_backend("qasm_simulator")
result = sim.run(qobj).result()
print('Status: {}'.format(result.status))
print("Results for parameterized circuit:")
for j in range(num_parameterizations):
    print(result.get_counts(j))

Which prints 10 counts:

Status: COMPLETED
Results for parameterized circuit:
{'0': 1013, '1': 11}
{'0': 884, '1': 140}
{'0': 993, '1': 31}
{'0': 894, '1': 130}
{'0': 981, '1': 43}
{'0': 847, '1': 177}
{'0': 806, '1': 218}
{'0': 883, '1': 141}
{'0': 798, '1': 226}
{'0': 860, '1': 164}

[hhorii]

@chriseclectic thanks. you are right. I misunderstood the current impl. Let me close this PR.