Add mid-circuit measurement and classical feedforward - #5
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Implements the mid-circuit-measurement OpenSpec change: - AST: QEffectMeasure, QEffectConditional dataclasses; new optional fields on QActionSignature (mid_circuit_measure, conditional_gate) - Parser: recognize measure(qs[N]) -> bits[M] and if bits[M] == val: Gate(qs[K]) effect syntax; list<bit> context fields parsed as QTypeList(element_type="bit") - Qiskit compiler: QuantumCircuit(n_qubits, n_bits) for classical registers; emit qc.measure() mid-circuit and with qc.if_test() feedforward blocks; BFS no longer halts at mid-circuit measurement events - QASM compiler: emit c[M] = measure q[N]; inline and if(c==val) gate q[K]; terminal measurement block suppressed when mid-circuit measurements are present - Verifier: check_mid_circuit_coherence (errors on unitary gate after measured qubit) and check_feedforward_completeness (warns on unused measurement result); _has_rule now matches custom_name for custom rules - Examples: active-teleportation.q.orca.md, bit-flip-syndrome.q.orca.md - Tests: 21 new tests covering parser, Qiskit, QASM, and verifier paths (331 passed, 1 skipped — no regressions) Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Replace if(c==val) (OpenQASM 2, whole-register comparison) with
if (c[M] == val) { gate; } (OpenQASM 3.0, per-bit), consistent with
the OPENQASM 3.0; declaration at the top of every emitted file.
The old form gave wrong results for multi-bit classical registers:
if(c==1) on a 2-bit register tests c==01 in binary, not bit 0 alone.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
SUPERPOSITION_LEAK was firing for measure_alice_x/measure_s0 events because the check only looked at event names, not whether the action was a mid-circuit measurement (intentional, coherence-preserving) vs a terminal collapse. Add an action-level guard: skip the leak check when the transition's action has mid_circuit_measure set. Also fix check_mid_circuit_coherence BFS to continue past mid-circuit measurement transitions rather than stopping at them (terminal-only halt), enabling correct qubit reuse detection across the full circuit. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
'done' was declared in the events list but had no transitions, causing an ORPHAN_EVENT strict verify failure in CI. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Qiskit's QASM 3.0 importer requires single-bit conditions to be
'bit == bool' not 'bit == int'. Switch from:
if (c[M] == 1) { gate; }
to:
if (c[M]) { gate; } (value == 1)
if (!c[M]) { gate; } (value == 0)
Verified round-trip: both examples parse successfully through
qiskit.qasm3.loads() with depth and clbit counts intact.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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Summary
QEffectMeasureandQEffectConditionaldataclasses;QActionSignaturegainsmid_circuit_measureandconditional_gateoptional fieldsmeasure(qs[N]) -> bits[M]andif bits[M] == val: Gate(qs[K])effect syntax;list<bit>context fields are parsed asQTypeList(element_type="bit")QuantumCircuit(n_qubits, n_bits)when classical bits are present; emitsqc.measure()mid-circuit andwith qc.if_test((qc.clbits[M], val)):feedforward blocks; BFS traversal no longer halts at mid-circuit measurement eventsc[M] = measure q[N];inline in the gate sequence andif(c==val) gate q[K];for conditional gates; suppresses redundant terminal measurement block when mid-circuit measurements are presentcheck_mid_circuit_coherence(error if unitary gate applied to already-measured qubit);check_feedforward_completeness(warning if measurement result is never consumed);_has_rulenow also matchescustom_nameso custom rule names activate the new checksactive-teleportation.q.orca.md(3-qubit active teleportation with X/Z feedforward),bit-flip-syndrome.q.orca.md(5-qubit syndrome extraction with mid-circuit ancilla measurement)tests/test_mid_circuit_measurement.py— full suite is 331 passed, 1 skipped, 0 failuresTest plan
pytest tests/test_mid_circuit_measurement.py— 21/21 passpytest(full suite) — 331 passed, 1 skipped, no regressionsqc.if_testemission for correctness against IBM Dynamic Circuits docsif(c==val)clause is accepted by target simulators🤖 Generated with Claude Code