def test_least_squares_xeb_fidelity_from_expectations():
prng_state = np.random.get_state()
np.random.seed(0)
depolarization = 0.5
n_qubits = 5
dim = 2**n_qubits
n_circuits = 10
qubits = cirq.LineQubit.range(n_qubits)
measured_expectations_lin = []
exact_expectations_lin = []
measured_expectations_log = []
exact_expectations_log = []
uniform_expectations_log = []
for _ in range(n_circuits):
circuit = make_random_quantum_circuit(qubits, depth=12)
bitstrings = sample_noisy_bitstrings(
circuit, qubits, depolarization=depolarization, repetitions=5000
)
amplitudes = cirq.final_state_vector(circuit)
probabilities = cirq.state_vector_to_probabilities(amplitudes)
measured_expectations_lin.append(dim * np.mean(probabilities[bitstrings]))
exact_expectations_lin.append(dim * np.sum(probabilities**2))
measured_expectations_log.append(np.mean(np.log(dim * probabilities[bitstrings])))
exact_expectations_log.append(np.sum(probabilities * np.log(dim * probabilities)))
uniform_expectations_log.append(np.mean(np.log(dim * probabilities)))
with cirq.testing.assert_deprecated(
'Use cirq.experiments.xeb_fitting', deadline='v0.16', count=2
):
f_lin, r_lin = cirq.experiments.least_squares_xeb_fidelity_from_expectations(
measured_expectations_lin, exact_expectations_lin, [1.0] * n_circuits
)
f_log, r_log = cirq.experiments.least_squares_xeb_fidelity_from_expectations(
measured_expectations_log, exact_expectations_log, uniform_expectations_log
)
assert np.isclose(f_lin, 1 - depolarization, atol=0.01)
assert np.isclose(f_log, 1 - depolarization, atol=0.01)
np.testing.assert_allclose(np.sum(np.array(r_lin) ** 2), 0.0, atol=1e-2)
np.testing.assert_allclose(np.sum(np.array(r_log) ** 2), 0.0, atol=1e-2)
np.random.set_state(prng_state)
def test_least_squares_xeb_fidelity_from_probabilities():
prng_state = np.random.get_state()
np.random.seed(0)
depolarization = 0.5
n_qubits = 5
dim = 2**n_qubits
n_circuits = 10
qubits = cirq.LineQubit.range(n_qubits)
all_probabilities = []
observed_probabilities = []
for _ in range(n_circuits):
circuit = make_random_quantum_circuit(qubits, depth=12)
bitstrings = sample_noisy_bitstrings(
circuit, qubits, depolarization=depolarization, repetitions=5000
)
amplitudes = cirq.final_state_vector(circuit)
probabilities = cirq.state_vector_to_probabilities(amplitudes)
all_probabilities.append(probabilities)
observed_probabilities.append(probabilities[bitstrings])
# 2 deprecation warnings for each of the following
with cirq.testing.assert_deprecated(
'Use cirq.experiments.xeb_fitting', deadline='v0.16', count=6
):
f_lin, r_lin = cirq.least_squares_xeb_fidelity_from_probabilities(
dim, observed_probabilities, all_probabilities, None, True
)
f_log_np, r_log_np = cirq.least_squares_xeb_fidelity_from_probabilities(
dim, observed_probabilities, all_probabilities, np.log, True
)
f_log_math, r_log_math = cirq.least_squares_xeb_fidelity_from_probabilities(
dim, observed_probabilities, all_probabilities, math.log, False
)
assert np.isclose(f_lin, 1 - depolarization, atol=0.01)
assert np.isclose(f_log_np, 1 - depolarization, atol=0.01)
assert np.isclose(f_log_math, 1 - depolarization, atol=0.01)
np.testing.assert_allclose(np.sum(np.array(r_lin) ** 2), 0.0, atol=1e-2)
np.testing.assert_allclose(np.sum(np.array(r_log_np) ** 2), 0.0, atol=1e-2)
np.testing.assert_allclose(np.sum(np.array(r_log_math) ** 2), 0.0, atol=1e-2)
np.random.set_state(prng_state)
def _ref_simulate_2q_xeb_circuit(task: Dict[str, Any]):
"""Helper function for simulating a given (circuit, cycle_depth)."""
circuit_i = task['circuit_i']
cycle_depth = task['cycle_depth']
circuit = task['circuit']
param_resolver = task['param_resolver']
circuit_depth = cycle_depth * 2 + 1
assert circuit_depth <= len(circuit)
tcircuit = circuit[:circuit_depth]
tcircuit = cirq.resolve_parameters_once(tcircuit, param_resolver=param_resolver)
pure_sim = cirq.Simulator()
psi = pure_sim.simulate(tcircuit)
psi = psi.final_state_vector
pure_probs = cirq.state_vector_to_probabilities(psi)
return {'circuit_i': circuit_i, 'cycle_depth': cycle_depth, 'pure_probs': pure_probs}