| """Walking dynamic surface code circuit builder.""" |
| from __future__ import annotations |
|
|
| from typing import Dict, Optional |
|
|
| from surface_code_in_stem.noise_models import NoiseModel |
|
|
| from .base import DynamicLayout, StimStringBuilder, stabilizer_cycle |
|
|
|
|
| def walking_surface_code(distance: int, rounds: int, p: float, noise_model: Optional[NoiseModel] = None) -> str: |
| """Return a Stim circuit string for the walking surface code. |
| |
| Each cycle swaps which sublattice receives a reset so that every physical |
| qubit is refreshed every other round. Detectors stitch consecutive |
| measurements of the same plaquette to expose leakage-induced correlations. |
| """ |
|
|
| layout = DynamicLayout.build(distance) |
| index_to_coord = {idx: coord for coord, idx in layout.coord_to_index.items()} |
| builder = StimStringBuilder(coord_lookup=index_to_coord) |
| builder.qubit_coords() |
|
|
| prev_meas: Dict[tuple[float, float], int] = {} |
| orientations = (0, 1, 2, 3) |
| for cycle in range(rounds): |
| reset_data = cycle % 2 == 1 |
| measure_data = cycle % 2 == 1 |
| prev_meas = stabilizer_cycle( |
| builder, |
| layout, |
| p=p, |
| orientations=orientations, |
| gate="CX", |
| noise_model=noise_model, |
| reset_data=reset_data, |
| measure_data=measure_data, |
| prev_meas=prev_meas, |
| ) |
|
|
| data_indices = [layout.coord_to_index[c] for c in layout.datas[:distance]] |
| logical_meas = builder.measure(data_indices) |
| builder.observable(logical_meas) |
| return builder.build() |
|
|
