def test_partial_trace_gate_errors(backend):
gate = gates.PartialTrace(0, 1)
# attempt to create unitary matrix
with pytest.raises(ValueError):
gate._construct_unitary()
# attempt to call on state vector
state = np.random.random(16) + 1j * np.random.random(16)
with pytest.raises(RuntimeError):
gate(state)
def nqubits(self, n: int):
from qibo import gates
self._nqubits = n
if self.partition is None:
self.partition = list(range(n // 2 + n % 2))
if len(self.partition) <= self.nqubits // 2:
self.partition = [
i for i in range(self.nqubits) if i not in set(self.partition)
]
self.partial_trace = gates.PartialTrace(*self.partition)
self.partial_trace.nqubits = n
self.partial_trace.density_matrix = self.density_matrix
def test_partial_trace_gate(backend, qubit):
gate = gates.PartialTrace(qubit)
gate.density_matrix = True
initial_rho = random_density_matrix(3)
final_state = gate(np.copy(initial_rho))
zero_state = np.array([[1, 0], [0, 0]])
target_state = np.reshape(initial_rho, 6 * (2,))
if qubit == 0:
target_state = np.einsum("aBCabc,Dd->DBCdbc", target_state, zero_state)
elif qubit == 1:
target_state = np.einsum("AbCabc,Dd->ADCadc", target_state, zero_state)
elif qubit == 2:
target_state = np.einsum("ABcabc,Dd->ABDabd", target_state, zero_state)
target_state = np.reshape(target_state, (8, 8))
K.assert_allclose(final_state, target_state)
def nqubits(self, n: int):
from qibo import gates
if self._nqubits is not None and self._nqubits != n:
raise_error(
RuntimeError,
f"Changing EntanglementEntropy nqubits from {self._nqubits} to {n}."
)
self._nqubits = n
if self.partition is None:
self.partition = list(range(n // 2 + n % 2))
if len(self.partition) <= self.nqubits // 2:
self.partition = [
i for i in range(self.nqubits) if i not in set(self.partition)
]
self.partial_trace = gates.PartialTrace(*self.partition)
self.partial_trace.nqubits = n
self.partial_trace.density_matrix = self.density_matrix
