def test_observable_expectation_supported_qubits(executor):
executor = functools.partial(executor, noise_level=(0, ))
a, b, c = cirq.LineQubit.range(3)
circuit = cirq.Circuit(cirq.I(a), cirq.X.on(b), cirq.H.on(c))
# <Z0> = 1.
obs = Observable(PauliString(spec="Z", support=(0, )))
assert np.isclose(obs.expectation(circuit, executor), 1.0)
# <Z1> = -1.
obs = Observable(PauliString(spec="Z", support=(1, )))
assert np.isclose(obs.expectation(circuit, executor), -1.0)
# <Z2> = 0.
obs = Observable(PauliString(spec="Z", support=(2, )))
assert np.isclose(obs.expectation(circuit, executor), 0.0, atol=5e-2)
def test_observable_expectation_one_circuit(n, executor):
executor = functools.partial(executor, noise_level=(0, ))
qubits = cirq.LineQubit.range(n)
obs = Observable(PauliString(spec="X" * n))
circuit = cirq.Circuit(cirq.H.on_each(qubits))
expectation = obs.expectation(circuit, executor)
assert np.isclose(expectation, 1.0)
def test_observable_expectation_two_circuits(n, executor):
executor = functools.partial(executor, noise_level=(0, ))
obs = Observable(PauliString(spec="X" * n, coeff=-2.0),
PauliString(spec="Z" * n))
qubits = cirq.LineQubit.range(n)
circuit = cirq.Circuit(cirq.H.on_each(qubits))
expectation = obs.expectation(circuit, executor)
assert np.isclose(expectation, -2.0, atol=1e-1)