def ideal(self):
"""Return True if this error object is composed only of identity operations.
Note that the identity check is best effort and up to global phase."""
for circ in self.circuits:
try:
# Circuit-level identity check for clifford Circuits
clifford = Clifford(circ)
if clifford != Clifford(np.eye(2 * circ.num_qubits,
dtype=bool)):
return False
except QiskitError:
pass
# Component-wise check for non-Clifford circuits
for op, _, _ in circ:
if isinstance(op, IGate):
continue
if isinstance(op, PauliGate):
if op.params[0].replace('I', ''):
return False
else:
# Convert to Kraus and check if identity
kmats = Kraus(op).data
if len(kmats) > 1:
return False
if not is_identity_matrix(kmats[0],
ignore_phase=True,
atol=self.atol,
rtol=self.rtol):
return False
return True
def iden(self, num_qubits):
"""Initialize an identity group element"""
self._num_qubits = num_qubits
if self._group_gates_type:
return CNOTDihedral(num_qubits)
else:
return Clifford(np.eye(2 * num_qubits))
def iden(self, num_qubits):
"""Initialize an identity group element"""
self._num_qubits = num_qubits
if self._group_gates_type:
assert num_qubits <= 2, "num_qubits for CNOT-Dihedral RB should be 1 or 2"
return CNOTDihedral(num_qubits)
else:
return Clifford(np.eye(2 * num_qubits))
def __init__(self, data, validate=True):
"""Initialize a StabilizerState object.
Args:
data (StabilizerState or Clifford or Pauli or QuantumCircuit or
qiskit.circuit.Instruction):
Data from which the stabilizer state can be constructed.
validate (boolean): validate that the stabilizer state data is
a valid Clifford.
"""
# Initialize from another StabilizerState
if isinstance(data, StabilizerState):
self._data = data._data
# Initialize from a Pauli
elif isinstance(data, Pauli):
self._data = Clifford(data.to_instruction())
# Initialize from a Clifford, QuantumCircuit or Instruction
else:
self._data = Clifford(data, validate)
# Initialize
super().__init__(op_shape=OpShape.auto(num_qubits_r=self._data.num_qubits, num_qubits_l=0))
def reset(self, qargs=None):
"""Reset state or subsystems to the 0-state.
Args:
qargs (list or None): subsystems to reset, if None all
subsystems will be reset to their 0-state
(Default: None).
Returns:
StabilizerState: the reset state.
Additional Information:
If all subsystems are reset this will return the ground state
on all subsystems. If only some subsystems are reset this
function will perform a measurement on those subsystems and
evolve the subsystems so that the collapsed post-measurement
states are rotated to the 0-state. The RNG seed for this
sampling can be set using the :meth:`seed` method.
"""
# Resetting all qubits does not require sampling or RNG
if qargs is None:
return StabilizerState(
Clifford(np.eye(2 * self.clifford.num_qubits)))
randbits = self._rng.integers(2, size=len(qargs))
ret = self.copy()
for bit, qubit in enumerate(qargs):
# Apply measurement and get classical outcome
outcome = ret._measure_and_update(qubit, randbits[bit])
# Use the outcome to apply X gate to any qubits left in the
# |1> state after measure, then discard outcome.
if outcome == 1:
_append_x(ret.clifford, qubit)
return ret
def to_operator(self):
"""Convert state to matrix operator class"""
return Clifford(self.clifford).to_operator()