from collections.abc import Collection, Generator
from itertools import chain
from stim import Circuit
from ..detectors import Detectors
from ..layouts.layout import Layout
from ..models import Model
from .decorators import qec_circuit
# methods to have in this script
from .util import (
idle_iterator,
init_qubits,
init_qubits_iterator,
init_qubits_x0_iterator,
init_qubits_x1_iterator,
init_qubits_z0_iterator,
init_qubits_z1_iterator,
log_depolarize1_error_iterator,
log_meas,
log_meas_iterator,
log_meas_x_iterator,
log_meas_z_iterator,
log_x,
log_x_error_iterator,
log_x_iterator,
log_y_error_iterator,
log_z,
log_z_error_iterator,
log_z_iterator,
pauli_observable_x_iterator,
pauli_observable_y_iterator,
pauli_observable_z_iterator,
qubit_coords,
)
from .util import qec_round_iterator as qec_round_iterator_sc
__all__ = [
"qubit_coords",
"idle_iterator",
"log_meas",
"log_meas_iterator",
"log_meas_z_iterator",
"log_meas_x_iterator",
"log_x",
"log_x_iterator",
"log_z",
"log_z_iterator",
"init_qubits",
"init_qubits_iterator",
"init_qubits_z0_iterator",
"init_qubits_z1_iterator",
"init_qubits_x0_iterator",
"init_qubits_x1_iterator",
"qec_round",
"qec_round_iterator",
"log_x_error_iterator",
"log_y_error_iterator",
"log_z_error_iterator",
"log_depolarize1_error_iterator",
"gate_to_iterator",
"pauli_observable_x_iterator",
"pauli_observable_y_iterator",
"pauli_observable_z_iterator",
]
[docs]
def qec_round(
model: Model,
layout: Layout,
detectors: Detectors,
anc_reset: bool = True,
anc_detectors: Collection[str] | None = None,
) -> Circuit:
"""
Returns stim circuit corresponding to a QEC round
of the given model.
Parameters
----------
model
Noise model for the gates.
layout
Code layout.
detectors
Detector object to use for their definition.
anc_reset
If ``True``, ancillas are reset at the beginning of the QEC round.
By default ``True``.
anc_detectors
List of ancilla qubits for which to define the detectors.
If ``None``, adds all detectors.
By default ``None``.
Notes
-----
This implementation follows two schedules, depending on the layout's interaction order:
https://doi.org/10.1103/PhysRevApplied.8.034021
or
shallowest interaction order for the rotated surface code where ancillas interact
with the data qubit on the left and right in just two two-qubit-gate layers.
It activates all the ancillas in ``detectors`` to always build the detectors.
As this function should not be used when building encoded circuits with
the iterating functions, it does not matter if the detectors are activated or not.
"""
circuit = sum(
qec_round_iterator(model=model, layout=layout, anc_reset=anc_reset),
start=Circuit(),
)
# add detectors
anc_qubits = layout.anc_qubits
if anc_detectors is None:
anc_detectors = anc_qubits
if set(anc_detectors) > set(anc_qubits):
raise ValueError("Elements in 'anc_detectors' are not ancilla qubits.")
# activate detectors so that "Detectors.build_from_anc" always populates
# the stim detector definitions.
inactive_dets = set(anc_detectors).difference(detectors.detectors)
detectors.activate_detectors(inactive_dets)
circuit += detectors.build_from_anc(
model.meas_target, anc_reset, anc_qubits=anc_detectors
)
return circuit
@qec_circuit
def qec_round_iterator(
model: Model,
layout: Layout,
anc_reset: bool = True,
) -> Generator[Circuit]:
"""
Yields stim circuit blocks which as a whole correspond to a QEC round
of the given model without the detectors.
Parameters
----------
model
Noise model for the gates.
layout
Code layout.
anc_reset
If ``True``, ancillas are reset at the beginning of the QEC round.
By default ``True``.
Notes
-----
This implementation follows two schedules, depending on the layout's interaction order:
https://doi.org/10.1103/PhysRevApplied.8.034021
or
shallowest interaction order for the rotated surface code where ancillas interact
with the data qubit on the left and right in just two two-qubit-gate layers.
"""
if layout.code not in ("repetition_code", "repetition_stability"):
raise TypeError(
f"The given layout is not a repetition code, but a {layout.code}"
)
if "steps" not in layout.interaction_order:
yield from qec_round_iterator_sc(model, layout, anc_reset=anc_reset)
return # finish generator
data_qubits = layout.data_qubits
anc_qubits = layout.anc_qubits
qubits = set(layout.qubits)
int_order = layout.interaction_order.copy()
mapping = {
"left": ("north_west", "south_west"),
"right": ("north_east", "south_east"),
}
int_order["steps"] = [mapping[i] for i in int_order["steps"]]
stab_type = (
"z_type"
if len(layout.get_qubits(role="anc", stab_type="x_type")) == 0
else "x_type"
)
yield model.incoming_noise(data_qubits)
yield model.tick()
if anc_reset:
yield model.reset(anc_qubits) + model.idle(data_qubits)
yield model.tick()
# a
rot_qubits = set(anc_qubits)
if stab_type == "x_type":
rot_qubits.update(data_qubits)
idle_qubits = qubits - rot_qubits
yield model.hadamard(rot_qubits) + model.idle(idle_qubits)
yield model.tick()
# b
int_pairs: list[tuple[str, str]] = []
for ord_dir in int_order["steps"][0]:
int_pairs.extend(
layout.get_neighbors(anc_qubits, direction=ord_dir, as_pairs=True)
)
int_qubits = list(chain.from_iterable(int_pairs))
idle_qubits = qubits - set(int_qubits)
yield model.cphase(int_qubits) + model.idle(idle_qubits)
yield model.tick()
# c
int_pairs = []
for ord_dir in int_order["steps"][1]:
int_pairs += layout.get_neighbors(anc_qubits, direction=ord_dir, as_pairs=True)
int_qubits = list(chain.from_iterable(int_pairs))
idle_qubits = qubits - set(int_qubits)
yield model.cphase(int_qubits) + model.idle(idle_qubits)
yield model.tick()
# d
rot_qubits = set(anc_qubits)
if stab_type == "x_type":
rot_qubits.update(data_qubits)
idle_qubits = qubits - rot_qubits
yield model.hadamard(rot_qubits) + model.idle(idle_qubits)
yield model.tick()
# e
yield model.measure(anc_qubits) + model.idle(data_qubits)
yield model.tick()
gate_to_iterator = {
"TICK": qec_round_iterator,
"I": idle_iterator,
"X": log_x_iterator,
"Z": log_z_iterator,
"R": init_qubits_z0_iterator,
"RZ": init_qubits_z0_iterator,
"RX": init_qubits_x0_iterator,
"M": log_meas_z_iterator,
"MZ": log_meas_z_iterator,
"MX": log_meas_x_iterator,
"X_ERROR": log_x_error_iterator,
"Y_ERROR": log_y_error_iterator,
"Z_ERROR": log_z_error_iterator,
"DEPOLARIZE1": log_depolarize1_error_iterator,
}
