Qubit ZooDescription
A surface-code logical qubit is not a new physical modality, but a fault-tolerant logical qubit encoded across a 2D lattice of physical qubits using repeated stabilizer measurements.
Logical information is stored nonlocally; errors are detected via local parity checks and corrected by decoding syndrome histories.
Figure
Hamiltonian / Stabilizers
The code space is defined by star and plaquette stabilizers:
with code Hamiltonian form:
Logical operators correspond to non-contractible strings across the patch.
Why it matters
Surface code is currently the dominant QEC architecture for superconducting and trapped-ion roadmaps due to high threshold (~1%) and local nearest-neighbor constraints.
Key Metrics
| Metric | Value | Notes | Fidelity reference |
|---|---|---|---|
| Threshold | ~1% | Circuit-level threshold | — |
| Physical qubits per logical | O(d²) | Code distance d | — |
| Stabilizer cycle time | 0.5–5 μs | Platform dependent | — |
| Current status | Early logical demonstrations | Below full fault tolerance | — |