Expand description
MWPM (Minimum-Weight Perfect Matching) decoder for the rotated surface code.
§Algorithm
In the surface code, syndrome ancillas form the nodes of a matching graph, and data qubits are the EDGES. Each data qubit connects exactly the 1 or 2 syndrome ancillas that contain it in their stabilizer support:
- If qubit q is in 2 Z-stab supports (A and B), it is the edge A↔B.
- If qubit q is in only 1 Z-stab support A, it is the edge A↔virtual_boundary. The boundary type (top/bottom/left/right) is determined by (row, col) of q.
We build this qubit→edge map, run Floyd-Warshall on the ancilla graph to get shortest distances, then run bitmask-DP MWPM on the defect subgraph.
Corrections are lifted by walking parent pointers in the ancilla graph.
Structs§
- Mwpm
Surface Decoder - MWPM decoder for the rotated planar surface code.