# 📐  L2 Digital Twin — Surface-Code Decoder Twin

**ID:** `L2-921` · **Status:** ⊙ Testnet (genesis catalog)
**Parents:** ⬆ Principle [`L1-921`](/artifact/l1/L1-921)

> **🎯 Tolerance (ε):** expression
> **⚖ Difficulty score:** 0.9 · **Delta tier:** 50

---

## 1. Domain Ω

**Type:** `range`

| Parameter | Unit | Range |
|---|---|---|
| Noise | — | depolarizing|biased|leakage |
| Code distance | — | 3 – 25 |
| Physical error | — | 0.0005 – 0.01 |

## 2. Tolerance (ε)

**Type:** `fn`

```
below-threshold scaling (Λ > 1); real-time decode latency within the cycle budget
```

## 3. Difficulty

| Property | Value |
|---|---|
| Difficulty score | 0.9 |
| Delta tier | 50 |

## 4. Fingerprint

`6783225549f8a391267f4fa0bdf8639823ca5afade7c9f75c3c9630a31f4a913`

---

## File Mapping

This bundle consists of: `L2-921.md`, `L2-921.json`.

| File | Role | How to regenerate |
|------|------|-------------------|
| `L2-921.md` | Source of truth — edit this | Human or LLM |
| `L2-921.json` | Structured metadata for the registry | LLM regenerates from the sections above |

**Prompt for your LLM after editing this Markdown:**

> Read the attached Markdown. Regenerate the sibling `.json` so every field matches.
> Preserve the schema documented in the rows above.
> Output each file in its own fenced code block tagged with the filename.
> Output only the JSON object.

_This Markdown was auto-synthesized from the catalog row for `L2-921`._
_Edit it, regenerate the JSON, and submit at [/submit](/submit) to claim the artifact._