def test_cannot_deallocate_same_qubit():
mapper = BoundedQubitMapper(1)
engine = MainEngine(
Simulator(),
engine_list=[mapper],
verbose=True,
)
qureg = engine.allocate_qubit()
qubit_id = qureg[0].id
engine.deallocate_qubit(qureg[0])
with pytest.raises(RuntimeError) as excinfo:
deallocate_cmd = Command(
engine=engine,
gate=DeallocateQubitGate(),
qubits=([WeakQubitRef(engine=engine, idx=qubit_id)], ),
tags=[LogicalQubitIDTag(qubit_id)],
)
engine.send([deallocate_cmd])
assert str(excinfo.value
) == "Cannot deallocate a qubit that is not already allocated!"
def test_cannot_deallocate_unknown_qubit():
engine = MainEngine(
Simulator(),
engine_list=[BoundedQubitMapper(1)],
verbose=True,
)
qureg = engine.allocate_qubit()
with pytest.raises(RuntimeError) as excinfo:
deallocate_cmd = Command(
engine=engine,
gate=DeallocateQubitGate(),
qubits=([WeakQubitRef(engine=engine, idx=1)], ),
tags=[LogicalQubitIDTag(1)],
)
engine.send([deallocate_cmd])
assert str(excinfo.value
) == "Cannot deallocate a qubit that is not already allocated!"
# but we can still deallocate an already allocated one
engine.deallocate_qubit(qureg[0])
del qureg
del engine
def test_unitary_after_deallocation_or_measurement():
eng = MainEngine(backend=UnitarySimulator(), engine_list=[])
qubit = eng.allocate_qubit()
X | qubit
assert not eng.backend.history
eng.flush()
Measure | qubit
# FlushGate and MeasureGate do not append to the history
assert not eng.backend.history
assert np.allclose(eng.backend.unitary, X.matrix)
with pytest.warns(UserWarning):
Y | qubit
# YGate after FlushGate and MeasureGate does not append current unitary (identity) to the history
assert len(eng.backend.history) == 1
assert np.allclose(eng.backend.unitary,
Y.matrix) # Reset of unitary when applying Y above
assert np.allclose(eng.backend.history[0], X.matrix)
# Still ok
eng.flush()
Measure | qubit
# FlushGate and MeasureGate do not append to the history
assert len(eng.backend.history) == 1
assert np.allclose(eng.backend.unitary, Y.matrix)
assert np.allclose(eng.backend.history[0], X.matrix)
# Make sure that the new gate will trigger appending to the history and modify the current unitary
with pytest.warns(UserWarning):
Rx(1) | qubit
assert len(eng.backend.history) == 2
assert np.allclose(eng.backend.unitary, Rx(1).matrix)
assert np.allclose(eng.backend.history[0], X.matrix)
assert np.allclose(eng.backend.history[1], Y.matrix)
# --------------------------------------------------------------------------
eng = MainEngine(backend=UnitarySimulator(), engine_list=[])
qureg = eng.allocate_qureg(2)
All(X) | qureg
XX_matrix = np.kron(X.matrix, X.matrix)
assert not eng.backend.history
assert np.allclose(eng.backend.unitary, XX_matrix)
eng.deallocate_qubit(qureg[0])
assert not eng.backend.history
with pytest.warns(UserWarning):
Y | qureg[1]
# An internal call to flush() happens automatically since the X
# gate occurs as the simulator is in an invalid state (after qubit
# deallocation)
assert len(eng.backend.history) == 1
assert np.allclose(eng.backend.history[0], XX_matrix)
assert np.allclose(eng.backend.unitary, Y.matrix)
# Still ok
eng.flush()
Measure | qureg[1]
# Nothing should have changed
assert len(eng.backend.history) == 1
assert np.allclose(eng.backend.history[0], XX_matrix)
assert np.allclose(eng.backend.unitary, Y.matrix)
