Bounded leakage runtime

Purpose and scope

Proposes a distinct three-level local model for leaving the computational qubit subspace. The third level is neither an ordinary bit value nor another name for a 2×2 qubit channel.

Core design rules

• browser-leakage-density is a separate target with a bounded backend.
• Gate embedding, typed leakage channels and leakage-aware measurement require explicit rules.
• Results distinguish leakage probabilities and three-level state evidence from ordinary qubit results.

Example from the original

This example illustrates the design recorded in the original. It is not by itself a claim of executable or stable support; check required options and the current version.

@target("browser-leakage-density");
@leakage_profile("package.lab.leakage@1.0.0", "reference_profile");

qreg q[2];
sample 1024 {
  X(q[0]);
  CNOT(q[0], q[1]);
  measure_leakage_aware(q[0]);
  measure_leakage_aware(q[1]);
}

Limits and interpretation

• The model does not change existing QReg<N> meaning or stabilizer/statevector results.
• A three-level local simulation is not evidence of a device's leakage rate or fault tolerance.

Status and implementation boundary

The source is proposed and requires a separate pre-implementation review. Requests for timed rates additionally depend on the binding conditions in NM-RFC-0019.