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Surface Code Sandbox

Learn Quantum Error Correction end to end. Inject Pauli errors onto a surface-code patch, watch the stabilizers detect syndromes live, then run a minimum-weight matching decoder to correct them — and see whether a logical error slipped through. Hover any qubit or stabilizer to trace what it touches.

Surface Code Distance (d)

Error Injection Mode

Select an error type below, then click on the circular data qubits in the grid to flip their state.

Syndrome (live)

Errors

Defects

Z-defects

X-defects

Actions

Noise p 5%

Legend

Data qubit (stores logical information)

Z-stabilizer (detects X errors)

X-stabilizer (detects Z errors)

X-correction chain (from matching)

Z-correction chain

The decoder pairs syndrome defects into minimum-weight correction chains (matching to a boundary when cheaper), applies them, then checks if the residual error is a non-trivial logical operator.