Status: runtime-experimental Contract: 0.2.0-runtime-experimental Default: disabled Owner: language / compiler

1. Problem

N/M 0.1 already supports @target and advisory @constraints warnings. Those surfaces help exploration, but they do not let a source artifact fail closed when a selected target lacks a required native gate set, exact topology, or bounded reference error budget. A warning-only profile is insufficient for reproducible compilation policy.

NM-RFC-0006 adds an explicitly negotiated, typed assertion:

module native_bell;
@target("superconducting");
@target_capabilities(profile: "superconducting", gate_set: ["H", "CNOT"], connectivity: "line", max_error: 0.08);

fn main() {
  let q: QReg<2> = qreg[2];
  H(q[0]);
  CNOT(q[0], q[1]);
  return q;
}

Stable N/M 0.1 behavior is unchanged. The annotation is accepted only when experimental.targetCapabilityConstraints=true is negotiated.

2. Fields and bounds

Tablo 1
Field	Contract
`profile`	Required registered target id; ASCII lowercase/digit/hyphen, at most 64 UTF-8 bytes.
`gate_set`	Optional closed-world list of 1–32 unique N/M gates. Every source gate must be declared and every declared/source gate must be native on the profile.
`connectivity`	Optional exact `all-to-all`, `line`, or `grid`; no implicit topology subsumption.
`max_error`	Optional finite value in `[1e-9, 1]`; compared with the bounded reference profile estimate.

At least one of gate_set, connectivity, or max_error is required in addition to profile. The annotation is line-oriented, must fit on one source line, is limited to 2,048 UTF-8 bytes, and may occur once.

3. Evidence

Successful analysis publishes a deterministic object containing:

contract version, required profile and explicit @target;
sorted required, missing, and undeclared source gate sets;
required/actual connectivity and exact-match result;
maximum/estimated error, evidence source and pass result;
aggregate passed state.

The bounded reference error estimate is:

text

1 - (1-p1)^single × (1-p2)^two × (1-p3)^three × (1-pm)^measurement

Reference rates are versioned educational profile data. They are not live hardware calibration, an SLA, a provider claim, or a substitute for signed calibration evidence.

4. Diagnostics

Tablo 2
Code	Meaning
`NM-PARSE-064`	Feature was used without explicit negotiation.
`NM-PARSE-065`	Annotation, field, duplicate, type, or bound is invalid.
`NM-TARGET-040`	Profile is unknown or conflicts with `@target`.
`NM-TARGET-041`	Closed/native gate-set contract fails.
`NM-TARGET-042`	Exact topology contract fails.
`NM-TARGET-043`	Reference error evidence is unavailable or exceeds the budget.

All failures are errors. The compiler/runtime must not silently lower, infer topology compatibility, substitute a profile, or fabricate error evidence after a failed constraint.

5. Carrier and compatibility

The canonical printer preserves field order: profile, gate_set, connectivity, max_error. JSON IR and the strict OpenQASM 3 sidecar preserve the typed requirement, negotiation version, and evidence. OpenQASM 2 cannot carry this contract and must report the gap.

Unknown fields, profiles, gate names, carrier fields, or future contract versions fail closed. No persistent artifact migration is promised while the feature remains experimental.

6. Non-goals

claiming live hardware availability, queue state, fidelity, or SLA;
selecting a provider or executing a quantum job;
treating one topology as implicitly satisfying another;
automatically widening the declared gate set after lowering;
signed calibration, attestation, or calibration freshness policy;
pulse-level capabilities and dynamic-circuit feature negotiation.