def __init__(self, num_qubits: int, initial_state: int = 0) -> None:
"""Initializes StabilizerStateChForm
Args:
num_qubits: The number of qubits in the system.
initial_state: The computational basis representation of the
state as a big endian int.
"""
self.n = num_qubits
# The state is represented by a set of binary matrices and vectors.
# See Section IVa of Bravyi et al
self.G = np.eye(self.n, dtype=bool)
self.F = np.eye(self.n, dtype=bool)
self.M = np.zeros((self.n, self.n), dtype=bool)
self.gamma = np.zeros(self.n, dtype=int)
self.v = np.zeros(self.n, dtype=bool)
self.s = np.zeros(self.n, dtype=bool)
self.omega = 1 # type: complex
# Apply X for every non-zero element of initial_state
for (i, val) in enumerate(
big_endian_int_to_digits(initial_state,
digit_count=num_qubits,
base=2)):
if val:
protocols.act_on(
pauli_gates.X,
clifford.ActOnStabilizerCHFormArgs(self, [i],
np.random.RandomState(),
{}),
)
def _create_partial_act_on_args(
self,
initial_state: Union[int, 'cirq.ActOnStabilizerCHFormArgs'],
qubits: Sequence['cirq.Qid'],
classical_data: 'cirq.ClassicalDataStore',
) -> 'cirq.ActOnStabilizerCHFormArgs':
"""Creates the ActOnStabilizerChFormArgs for a circuit.
Args:
initial_state: The initial state for the simulation in the
computational basis. Represented as a big endian int.
qubits: Determines the canonical ordering of the qubits. This
is often used in specifying the initial state, i.e. the
ordering of the computational basis states.
logs: A log of the results of measurement that is added to.
classical_data: The shared classical data container for this
simulation.
Returns:
ActOnStabilizerChFormArgs for the circuit.
"""
if isinstance(initial_state, clifford.ActOnStabilizerCHFormArgs):
return initial_state
return clifford.ActOnStabilizerCHFormArgs(
prng=self._prng,
classical_data=classical_data,
qubits=qubits,
initial_state=initial_state,
)
def _create_partial_act_on_args(
self,
initial_state: Union[int, clifford.ActOnStabilizerCHFormArgs],
qubits: Sequence['cirq.Qid'],
logs: Dict[str, Any],
) -> clifford.ActOnStabilizerCHFormArgs:
"""Creates the ActOnStabilizerChFormArgs for a circuit.
Args:
initial_state: The initial state for the simulation in the
computational basis. Represented as a big endian int.
qubits: Determines the canonical ordering of the qubits. This
is often used in specifying the initial state, i.e. the
ordering of the computational basis states.
logs: A log of the results of measurement that is added to.
Returns:
ActOnStabilizerChFormArgs for the circuit.
"""
if isinstance(initial_state, clifford.ActOnStabilizerCHFormArgs):
return initial_state
qubit_map = {q: i for i, q in enumerate(qubits)}
state = CliffordState(qubit_map, initial_state=initial_state)
return clifford.ActOnStabilizerCHFormArgs(
state=state.ch_form,
prng=self._prng,
log_of_measurement_results=logs,
qubits=qubits,
)
def apply_measurement(
self,
op: 'cirq.Operation',
measurements: Dict[str, List[np.ndarray]],
prng: np.random.RandomState,
collapse_state_vector=True,
):
if not isinstance(op.gate, cirq.MeasurementGate):
raise TypeError(
'apply_measurement only supports cirq.MeasurementGate operations. Found %s instead.'
% str(op.gate))
if collapse_state_vector:
state = self
else:
state = self.copy()
classical_data = value.ClassicalDataDictionaryStore()
ch_form_args = clifford.ActOnStabilizerCHFormArgs(
prng=prng,
classical_data=classical_data,
qubits=self.qubit_map.keys(),
initial_state=state.ch_form,
)
act_on(op, ch_form_args)
measurements.update(
{str(k): list(v[-1])
for k, v in classical_data.records.items()})
def apply_unitary(self, op: 'cirq.Operation'):
ch_form_args = clifford.ActOnStabilizerCHFormArgs(
self.ch_form, np.random.RandomState(), {}, self.qubit_map.keys())
try:
act_on(op, ch_form_args)
except TypeError:
raise ValueError(
f'{str(op.gate)} cannot be run with Clifford simulator.'
) # type: ignore
return
def _base_iterator(
self, circuit: circuits.Circuit, qubit_order: ops.QubitOrderOrList,
initial_state: int
) -> Iterator['cirq.CliffordSimulatorStepResult']:
"""Iterator over CliffordSimulatorStepResult from Moments of a Circuit
Args:
circuit: The circuit to simulate.
qubit_order: Determines the canonical ordering of the qubits. This
is often used in specifying the initial state, i.e. the
ordering of the computational basis states.
initial_state: The initial state for the simulation in the
computational basis. Represented as a big endian int.
Yields:
CliffordStepResult from simulating a Moment of the Circuit.
"""
qubits = ops.QubitOrder.as_qubit_order(qubit_order).order_for(
circuit.all_qubits())
qubit_map = {q: i for i, q in enumerate(qubits)}
if len(circuit) == 0:
yield CliffordSimulatorStepResult(measurements={},
state=CliffordState(
qubit_map,
initial_state=initial_state))
return
state = CliffordState(qubit_map, initial_state=initial_state)
ch_form_args = clifford.ActOnStabilizerCHFormArgs(
state.ch_form,
[],
self._prng,
{},
)
for moment in circuit:
ch_form_args.log_of_measurement_results = {}
for op in moment:
try:
ch_form_args.axes = tuple(state.qubit_map[i]
for i in op.qubits)
act_on(op, ch_form_args)
except TypeError:
raise NotImplementedError(
f"CliffordSimulator doesn't support {op!r}"
) # type: ignore
yield CliffordSimulatorStepResult(
measurements=ch_form_args.log_of_measurement_results,
state=state)
def apply_unitary(self, op: 'cirq.Operation'):
tableau_args = clifford.ActOnCliffordTableauArgs(
self.tableau, [self.qubit_map[i] for i in op.qubits],
np.random.RandomState(), {})
ch_form_args = clifford.ActOnStabilizerCHFormArgs(
self.ch_form, [self.qubit_map[i] for i in op.qubits])
try:
act_on(op, tableau_args)
act_on(op, ch_form_args)
except TypeError:
raise ValueError('%s cannot be run with Clifford simulator.' %
str(op.gate)) # type: ignore
return
def apply_measurement(
self,
op: 'cirq.Operation',
measurements: Dict[str, List[np.ndarray]],
prng: np.random.RandomState,
collapse_state_vector=True,
):
if not isinstance(op.gate, cirq.MeasurementGate):
raise TypeError(
'apply_measurement only supports cirq.MeasurementGate operations. Found %s instead.'
% str(op.gate))
if collapse_state_vector:
state = self
else:
state = self.copy()
ch_form_args = clifford.ActOnStabilizerCHFormArgs(
state.ch_form, prng, measurements, self.qubit_map.keys())
act_on(op, ch_form_args)
