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random_circuit

random_circuit

The x/random_circuit module (formerly x/qcledger) is Problem #1 in daqq’s Problem System. It records participants’ theoretical output probability distributions for the random quantum circuit generated from each beacon round’s seed.

Case A vs Case B — x/random_circuit handles the analytical/theoretical distribution (Case A). A future x/random_circuit_sampling module will handle empirical shot histograms (Case B) as a separate problem in the registry.

Registration with x/problems

x/random_circuit registers itself in the problems registry at chain genesis. Look it up by name:

quantumchaind query problems get-problem-by-name random_circuit
problem:
  id: "1"
  name: random_circuit
  module_name: random_circuit
  kind: PROBLEM_KIND_BUILTIN
  enabled: true
  description: Theoretical output distribution of a randomly generated quantum circuit (case A).

The keeper persists the assigned ProblemID in its own store so other modules and clients can derive it without re-querying.

Dependency on beacon

Every submission carries a roundID. Before accepting it, the handler calls:

// quantum-chain/x/random_circuit/keeper/msg_server_submit_result.go
_, err := k.beaconKeeper.GetSeed(ctx, msg.RoundId)
if err != nil {
    return nil, errorsmod.Wrapf(types.ErrSeedNotReady, "seed for round %d not ready", msg.RoundId)
}

This guarantees:

  1. Every recorded result is tied to a seed every node already agrees on.
  2. Honest nodes generating the same circuit from that seed produce the same expected output, making divergent results easy to spot.

Submission shape

MsgSubmitResult carries the participant’s full theoretical distribution:

message MsgSubmitResult {
  string creator = 1;
  uint64 round_id = 2;
  Distribution distribution = 3;
}

message Distribution {
  // basis state (e.g. "00101") -> probability as a decimal string
  map<string, string> probabilities = 1;
}

Probabilities are encoded as decimal strings to avoid floating-point divergence across nodes during consensus serialisation.

A submitter may submit at most one solution per (round, problem) pair. Re-submissions are rejected.

TODO

This page still needs:

  • Validation rules for Distribution (must sum to ~1, dimension = 2^width, byte cap).
  • Query endpoints for stored submissions.
  • Worked example of a full submit flow.
beaconproblems