def construct_QAOA(G,
p,
minimizer_kwargs={
'method': 'BFGS',
'options': {
'ftol': 1.0e-2,
'xtol': 1.0e-2,
'disp': True
}
},
init_betas=None,
init_gammas=None,
vqe_options={
'disp': print,
'return_all': True
}):
# setting up connection with the QVM
qvm_connection = api.QVMConnection()
# labelling qubits according to graph
qubits = [int(n) for n in list(G.nodes)]
# turning unweighted graphs into weighted graph with weight wij = 1
for (u, v) in G.edges():
if G.edges[u, v] == {}:
G.edges[u, v]['weight'] = 1
# constructing cost and mixer hamiltonian elements in list
# N.B. This algorithm only works if all the terms in the cost Hamiltonian commute with each other.
Hc = hamiltonians.cost(G)
Hb = hamiltonians.mixer(G)
return QAOA(qvm_connection,
qubits,
steps=p,
cost_ham=Hc,
ref_ham=Hb,
minimizer_kwargs=minimizer_kwargs,
vqe_options=vqe_options)
"""
Created on Thu Jul 2 13:37:11 2020
@author: joost
"""
from hamiltonians import cost,mixer
import networkx as nx
import pyquil.latex
import pyquil.api as api
from grove.pyqaoa.qaoa import QAOA
G = nx.random_regular_graph(2,3)
Hc = cost(G)
Hb = mixer(G)
qvm_connection = api.QVMConnection()
qubits = [int(n) for n in list(G.nodes)]
Q = QAOA(qvm_connection, qubits, steps=2,
cost_ham = Hc,
ref_ham= Hb)
params = [3,7,2,5] # b1, b2, g1, g2
prog = Q.get_parameterized_program()
circuit = prog(params)
# print to latex doc
s = pyquil.latex.to_latex(circuit)
print(s)
# close all earlier figures
plt.close('all')
# setting up connection with the QVM
qvm_connection = api.QVMConnection()
# constructing graph, setting p and the desired number of samples
G = nx.erdos_renyi_graph(5, 0.5)
qubits = [int(n) for n in list(G.nodes)]
p = 4
n_samples = 1024
# constructing cost and mixer hamiltonian elements in list
# N.B. This algorithm only works if all the terms in the cost Hamiltonian commute with each other.
Hc = hamiltonians.cost(G)
Hb = hamiltonians.mixer(G)
# setting up the QAOA circuit
initial_betas = 0.8
initial_gammas = 0.35
minimizer_kwargs = {
'method': 'BFGS',
'options': {
'ftol': 1.0e-2,
'xtol': 1.0e-2,
'disp': False
}
}
if type(initial_betas) == float:
p_start = 1
def interp_pyquil(G,
p,
initial_betas=0.8,
initial_gammas=0.35,
minimizer_kwargs={
'method': 'BFGS',
'options': {
'ftol': 1.0e-2,
'xtol': 1.0e-2,
'disp': True
}
},
n_samples=1024,
plot_hist=False):
# timing start
start = time.time()
# setting up connection with the QVM
qvm_connection = api.QVMConnection()
# labelling qubits according to graph
qubits = [int(n) for n in list(G.nodes)]
# turning unweighted graphs into weighted graph with weight wij = 1
for (u, v) in G.edges():
if G.edges[u, v] == {}:
G.edges[u, v]['weight'] = 1
# constructing cost and mixer hamiltonian elements in list
# N.B. This algorithm only works if all the terms in the cost Hamiltonian commute with each other.
Hc = hamiltonians.cost(G)
Hb = hamiltonians.mixer(G)
# saving data from all layers
results = {}
# Entering Loop
if type(initial_betas) == float:
p_start = 1
else:
p_start = len(initial_betas)
for i in range(p_start, p + 1):
QAOA_inst = QAOA(qvm_connection,
qubits,
steps=i,
cost_ham=Hc,
ref_ham=Hb,
init_betas=initial_betas,
init_gammas=initial_gammas,
minimizer_kwargs=minimizer_kwargs,
vqe_options={
'disp': print,
'return_all': True
})
# calculating angles using VQE (simulation)
print(" p =", i)
betas, gammas = QAOA_inst.get_angles()
print("Values of betas:", betas)
print("Values of gammas:", gammas, '\n')
# resulting bitstrings and the most common one
print("\nAnd the most common measurement is... ")
most_common_bitstring, results_counter = QAOA_inst.get_string(
betas, gammas, samples=n_samples)
print(most_common_bitstring)
print(tuple(qubits))
# graphing distribution
if plot_hist:
counter_histogram(results_counter, title=" p = " + str(p))
# timing final
end = time.time()
print("Time ", end - start)
# saving data from this layer
results_i = {}
results_i['p'] = i
results_i['time'] = end - start
results_i['graph'] = nx.to_dict_of_dicts(G)
results_i['n_nodes'] = len(G.nodes)
results_i['n_edges'] = len(G.edges)
results_i['most_common_bistring'] = most_common_bitstring
results_i['qubit_order'] = tuple(qubits)
results_i['counter'] = dict(results_counter)
results_i['n_Fp_evals'] = len(QAOA_inst.result['expectation_vals'])
results_i['n_samples'] = n_samples
results_i['Fp'] = -QAOA_inst.result['fun']
results_i['Fp_sampled'] = sum([
objective_value(G, k, qubits) * v
for k, v in results_counter.items()
]) / n_samples
results_i['cutvalue_best'] = cutvalue_best(G, results_counter, qubits)
results_i['cutvalue_most_sampled'] = cutvalue_most_sampled(
G, results_counter, qubits)
results_i['minimizer_method'] = minimizer_kwargs['method']
# time symmetry
if all(gammas > 0) and all(betas > 0):
results_i['gammas'] = gammas.copy()
results_i['betas'] = betas.copy()
else:
results_i['gammas'] = -gammas.copy()
results_i['betas'] = -betas.copy()
results[i] = results_i
# setting next angles
initial_betas = next_angles(betas)
initial_gammas = next_angles(gammas)
print("Values of betas ansatz:", initial_betas)
print("Values of gammas ansatz:", initial_gammas, '\n')
return results
def run_experiment(G,
p,
optimizer,
qvm_connection,
n_shots=8192,
print_result=False):
'''Runs (pyQuil) QAOA experiment with the given parameters
Inputs
Returns a dictionary with the following keys (some are yet to be implemented)
- energy
- time (in seconds)
- iterations
- max-cut objective
- solution
- solution objective
'''
n = len(G) # number of nodes / qubits
qubits = [int(n) for n in list(G.nodes)] # list of qubits
# constructing cost and mixer hamiltonian elements in list
Hc = hamiltonians.cost(G)
Hb = hamiltonians.mixer(G)
# setting up the QAOA circuit
initial_beta = 0
initial_gamma = 0
QAOA_inst = QAOA(qvm_connection,
qubits,
steps=p,
cost_ham=Hc,
ref_ham=Hb,
init_betas=initial_beta,
init_gammas=initial_gamma,
minimizer_kwargs=optimizer,
vqe_options={'samples': n_shots})
# calculating angles using VQE (simulation)
angles = QAOA_inst.get_angles()
betas, gammas = angles
# resulting bitstrings and the most common one
most_common_bitstring, results_counter = QAOA_inst.get_string(
betas, gammas, samples=n_shots)
# Results
energy = None
time = None
iterations = None
objective = None
solution = most_common_bitstring
solution_objective = None
distribution = results_counter
angles = angles
if print_result:
print('energy:', energy)
print('time:', time, 's')
print('max-cut objective:', objective)
print('solution:', solution)
print('solution objective:', solution_objective)
print('anlges:', angles)
return {
'energy': energy,
'time': time,
'iterations': iterations,
'max-cut objective': objective,
'solution': solution,
'solution objective': solution_objective,
'distribution': distribution,
'angles': angles
}
