def collect_heavy_outputs(wfn_sim: NumpyWavefunctionSimulator,
permutations: np.ndarray,
gates: np.ndarray) -> List[int]:
"""
Collects and returns those 'heavy' bitstrings which are output with greater than median
probability among all possible bitstrings on the given qubits.
The method uses the provided wfn_sim to calculate the probability of measuring each bitstring
from the output of the circuit comprised of the given permutations and gates.
:param wfn_sim: a NumpyWavefunctionSimulator that can simulate the provided program
:param permutations: array of depth-many arrays of size n_qubits indicating a qubit permutation
:param gates: depth by num_gates_per_layer many matrix representations of 2q gates.
The first row of matrices is the earliest-time layer of 2q gates applied.
:return: a list of the heavy outputs of the circuit, represented as ints
"""
wfn_sim.reset()
for layer_idx, (perm, layer) in enumerate(zip(permutations, gates)):
for gate_idx, gate in enumerate(layer):
wfn_sim.do_gate_matrix(gate, (perm[gate_idx], perm[gate_idx + 1]))
# Note that probabilities are ordered lexicographically with qubit 0 leftmost.
probabilities = np.abs(wfn_sim.wf.reshape(-1))**2
median_prob = median(probabilities)
# store the integer indices, which implicitly represent the bitstring outcome.
heavy_outputs = [
idx for idx, prob in enumerate(probabilities) if prob > median_prob
]
return heavy_outputs
def test_expectation_vs_ref_qvm(qvm, n_qubits):
for repeat_i in range(20):
prog = _generate_random_program(n_qubits=n_qubits, length=10)
operator = _generate_random_pauli(n_qubits=n_qubits, n_terms=5)
print(prog)
print(operator)
ref_wf = ReferenceWavefunctionSimulator(n_qubits=n_qubits).do_program(prog)
ref_exp = ref_wf.expectation(operator=operator)
np_wf = NumpyWavefunctionSimulator(n_qubits=n_qubits).do_program(prog)
np_exp = np_wf.expectation(operator=operator)
np.testing.assert_allclose(ref_exp, np_exp, atol=1e-15)
def test_exhaustive_state_dfe_run(benchmarker: BenchmarkConnection):
wfnsim = NumpyWavefunctionSimulator(n_qubits=1)
process = Program(X(0))
texpt = generate_exhaustive_state_dfe_experiment(program=process,
qubits=[0],
benchmarker=benchmarker)
for setting in texpt:
setting = setting[0]
prog = Program()
for oneq_state in setting.in_state.states:
prog += _one_q_state_prep(oneq_state)
prog += process
expectation = wfnsim.reset().do_program(prog).expectation(
setting.out_operator)
assert expectation == 1.
def test_qv_get_results_by_depth(qvm):
depths = [2, 3]
n_ckts = 10
n_shots = 5
ckt_results = []
ckt_hhs = []
for depth in depths:
wfn_sim = NumpyWavefunctionSimulator(depth)
for _ in range(n_ckts):
permutations, gates = generate_abstract_qv_circuit(depth)
program = _naive_program_generator(qvm, qvm.qubits(), permutations, gates)
program.wrap_in_numshots_loop(n_shots)
executable = qvm.compiler.native_quil_to_executable(program)
results = qvm.run(executable)
ckt_results.append(results)
heavy_outputs = collect_heavy_outputs(wfn_sim, permutations, gates)
ckt_hhs.append(heavy_outputs)
num_hh_sampled = count_heavy_hitters_sampled(ckt_results, ckt_hhs)
probs_by_depth = get_prob_sample_heavy_by_depth(depths, num_hh_sampled,
[n_shots for _ in depths])
assert len(probs_by_depth.keys()) == len(depths)
assert [0 <= probs_by_depth[d][1] <= probs_by_depth[d][0] <= 1 for d in depths]
def wfn_measure_observables(n_qubits, tomo_expt: TomographyExperiment):
if len(tomo_expt.program.defined_gates) > 0:
raise pytest.skip("Can't do wfn on defined gates yet")
wfn = NumpyWavefunctionSimulator(n_qubits)
for settings in tomo_expt:
for setting in settings:
prog = Program()
for oneq_state in setting.in_state.states:
prog += _one_q_state_prep(oneq_state)
prog += tomo_expt.program
yield ExperimentResult(
setting=setting,
expectation=wfn.reset().do_program(prog).expectation(setting.out_operator),
stddev=0.,
total_counts=1, # don't set to zero unless you want nans
)
def test_monte_carlo_process_dfe(benchmarker: BenchmarkConnection):
process = Program(CNOT(0, 1))
texpt = generate_monte_carlo_process_dfe_experiment(
program=process, qubits=[0, 1], n_terms=10, benchmarker=benchmarker)
assert len(texpt) == 10
wfnsim = NumpyWavefunctionSimulator(n_qubits=2)
for setting in texpt:
setting = setting[0]
prog = Program()
for oneq_state in setting.in_state.states:
prog += _one_q_state_prep(oneq_state)
prog += process
expectation = wfnsim.reset().do_program(prog).expectation(
setting.out_operator)
assert_almost_equal(expectation, 1., decimal=7)
def run(depth, circuit):
wfn_sim = NumpyWavefunctionSimulator(depth)
start = time.time()
heavy_outputs = collect_heavy_outputs(wfn_sim, *circuit)
end = time.time()
return heavy_outputs, end - start
def sample_rand_circuits_for_heavy_out(
qc: QuantumComputer,
qubits: Sequence[int],
depth: int,
program_generator: Callable[
[QuantumComputer, Sequence[int], Sequence[np.ndarray], np.ndarray],
Program],
num_circuits: int = 100,
num_shots: int = 1000,
show_progress_bar: bool = False) -> int:
"""
This method performs the bulk of the work in the quantum volume measurement.
For the given depth, num_circuits many random model circuits are generated, the heavy outputs
are determined from the ideal output distribution of each circuit, and a native quil
implementation of the model circuit output by the program generator is run on the qc. The total
number of sampled heavy outputs is returned.
:param qc: the quantum resource that will implement the PyQuil program for each model circuit
:param qubits: the qubits available in the qc for the program_generator to use.
:param depth: the depth (and width in num of qubits) of the model circuits
:param program_generator: a method which takes an abstract description of a model circuit and
returns a native quil program that implements that circuit. See measure_quantum_volume
docstring for specifics.
:param num_circuits: the number of random model circuits to sample at this depth; should be >100
:param num_shots: the number of shots to sample from each model circuit
:param show_progress_bar: displays a progress bar via tqdm if true.
:return: the number of heavy outputs sampled among all circuits generated for this depth
"""
wfn_sim = NumpyWavefunctionSimulator(depth)
num_heavy = 0
# display progress bar using tqdm
for _ in tqdm(range(num_circuits), disable=not show_progress_bar):
permutations, gates = generate_abstract_qv_circuit(depth)
# generate a PyQuil program in native quil that implements the model circuit
# The program should measure the output qubits in the order that is consistent with the
# comparison of the bitstring results to the heavy outputs given by collect_heavy_outputs
program = program_generator(qc, qubits, permutations, gates)
# run the program num_shots many times
program.wrap_in_numshots_loop(num_shots)
executable = qc.compiler.native_quil_to_executable(program)
results = qc.run(executable)
# classically simulate model circuit represented by the perms and gates for heavy outputs
heavy_outputs = collect_heavy_outputs(wfn_sim, permutations, gates)
# determine if each result bitstring is a heavy output, as determined from simulation
for result in results:
# convert result to int for comparison with heavy outputs.
output = bit_array_to_int(result)
if output in heavy_outputs:
num_heavy += 1
return num_heavy
def single_q_tomo_fixture():
qubits = [0]
qc = get_test_qc(n_qubits=len(qubits))
# Generate random unitary
u_rand = haar_rand_unitary(2 ** 1, rs=np.random.RandomState(52))
state_prep = Program().defgate("RandUnitary", u_rand)
state_prep.inst([("RandUnitary", qubits[0])])
# True state
wfn = NumpyWavefunctionSimulator(n_qubits=1)
psi = wfn.do_gate_matrix(u_rand, qubits=[0]).wf.reshape(-1)
rho_true = np.outer(psi, psi.T.conj())
# Get data from QVM
tomo_expt = generate_state_tomography_experiment(state_prep, qubits)
results = list(measure_observables(qc=qc, tomo_experiment=tomo_expt, n_shots=4000))
return results, rho_true
def two_q_tomo_fixture(test_qc):
qubits = [0, 1]
# Generate random unitary
u_rand1 = haar_rand_unitary(2 ** 1, rs=np.random.RandomState(52))
u_rand2 = haar_rand_unitary(2 ** 1, rs=np.random.RandomState(53))
state_prep = Program().defgate("RandUnitary1", u_rand1).defgate("RandUnitary2", u_rand2)
state_prep.inst(("RandUnitary1", qubits[0])).inst(("RandUnitary2", qubits[1]))
# True state
wfn = NumpyWavefunctionSimulator(n_qubits=2)
psi = wfn \
.do_gate_matrix(u_rand1, qubits=[0]) \
.do_gate_matrix(u_rand2, qubits=[1]) \
.wf.reshape(-1)
rho_true = np.outer(psi, psi.T.conj())
# Get data from QVM
tomo_expt = generate_state_tomography_experiment(state_prep, qubits)
results = list(estimate_observables(qc=test_qc, obs_expt=tomo_expt, num_shots=1000,
symm_type=-1))
results = list(calibrate_observable_estimates(test_qc, results))
return results, rho_true
def test_expectation():
wfn = NumpyWavefunctionSimulator(n_qubits=3)
val = wfn.expectation(0.4 * sZ(0) + sX(2))
assert val == 0.4
def objective_function(self, amps=None):
"""
This function returns the Hamiltonian expectation value over the final circuit output state. If argument
packed_amps is given, the circuit will run with those parameters. Otherwise, the initial angles will be used.
:param [list(), numpy.ndarray] amps: list of circuit angles to run the objective function over.
:return: energy estimate
:rtype: float
"""
E = 0
t = time.time()
if amps is None:
packed_amps = self.initial_packed_amps
elif isinstance(amps, np.ndarray):
packed_amps = amps.tolist()[:]
elif isinstance(amps, list):
packed_amps = amps[:]
else:
raise TypeError('Please supply the circuit parameters as a list or np.ndarray')
if self.tomography:
if (not self.parametric_way) and (self.strategy == 'UCCSD'): # modify hard-coded type ansatz circuit based
# on packed_amps angles
self.ansatz = uccsd_ansatz_circuit(packed_amps, self.molecule.n_orbitals,
self.molecule.n_electrons, cq=self.custom_qubits)
self.compile_tomo_expts()
for experiment in self.experiment_list:
E += experiment.run_experiment(self.qc, packed_amps) # Run tomography experiments
E += self.offset # add the offset energy to avoid doing superfluous tomography over the identity operator.
elif self.method == 'WFS':
# In the direct WFS method without tomography, direct access to wavefunction is allowed and expectation
# value is exact each run.
if self.parametric_way:
E += WavefunctionSimulator().expectation(self.ref_state+self.ansatz,
self.pauli_sum,
{'theta': packed_amps}).real # attach parametric angles here
else:
if packed_amps is not None: # modify hard-coded type ansatz circuit based on packed_amps angles
self.ansatz = uccsd_ansatz_circuit(packed_amps, self.molecule.n_orbitals,
self.molecule.n_electrons, cq=self.custom_qubits)
E += WavefunctionSimulator().expectation(self.ref_state+self.ansatz, self.pauli_sum).real
elif self.method == 'Numpy':
if self.parametric_way:
raise ValueError('NumpyWavefunctionSimulator() backend does not yet support parametric programs.')
else:
if packed_amps is not None:
self.ansatz = uccsd_ansatz_circuit(packed_amps,
self.molecule.n_orbitals,
self.molecule.n_electrons,
cq=self.custom_qubits)
E += NumpyWavefunctionSimulator(n_qubits=self.n_qubits).\
do_program(self.ref_state+self.ansatz).expectation(self.pauli_sum).real
elif self.method == 'linalg':
# check if molecule has data sufficient to construct UCCSD ansatz and propagate starting from HF state
if self.molecule is not None:
propagator = normal_ordered(uccsd_singlet_generator(packed_amps, 2 * self.molecule.n_orbitals,
self.molecule.n_electrons,
anti_hermitian=True))
qubit_propagator_matrix = get_sparse_operator(propagator, n_qubits=self.n_qubits)
uccsd_state = expm_multiply(qubit_propagator_matrix, self.initial_psi)
expected_uccsd_energy = expectation(self.hamiltonian_matrix, uccsd_state).real
E += expected_uccsd_energy
else: # apparently no molecule was supplied; attempt to just propagate the ansatz from user-specified
# initial state, using a circuit unitary if supplied by the user, otherwise the initial state itself,
# and then estimate over <H>
if self.initial_psi is None:
raise ValueError('Warning: no initial wavefunction set. Please set using '
'VQEexperiment().set_initial_state()')
# attempt to propagate with a circuit unitary
if self.circuit_unitary is None:
psi = self.initial_psi
else:
psi = expm_multiply(self.circuit_unitary, self.initial_psi)
E += expectation(self.hamiltonian_matrix, psi).real
else:
raise ValueError('Impossible method: please choose from method = {WFS, Numpy, linalg} if Tomography is set'
' to False, or choose from method = {QC, WFS, Numpy, linalg} if tomography is set to True')
if self.verbose:
self.it_num += 1
print('black-box function call #' + str(self.it_num))
print('Energy estimate is now: ' + str(E))
print('at angles: ', packed_amps)
print('and this took ' + '{0:.3f}'.format(time.time()-t) + ' seconds to evaluate')
self.history.append(E)
return E
