diff --git a/compiler/qsc/src/interpret/circuit_tests.rs b/compiler/qsc/src/interpret/circuit_tests.rs index 9de00e3d7b..2a5cbf7b49 100644 --- a/compiler/qsc/src/interpret/circuit_tests.rs +++ b/compiler/qsc/src/interpret/circuit_tests.rs @@ -72,6 +72,36 @@ fn one_gate() { .assert_eq(&circ.to_string()); } +#[test] +fn measure_same_qubit_twice() { + let mut interpreter = interpreter( + r" + namespace Test { + @EntryPoint() + operation Main() : Result[] { + use q = Qubit(); + H(q); + let r1 = M(q); + let r2 = M(q); + [r1, r2] + } + } + ", + Profile::Unrestricted, + ); + + let circ = interpreter + .circuit(CircuitEntryPoint::EntryPoint, false) + .expect("circuit generation should succeed"); + + expect![[r#" + q_0 ── H ──── M ──── M ── + ╘══════╪═══ + ╘═══ + "#]] + .assert_eq(&circ.to_string()); +} + #[test] fn toffoli() { let mut interpreter = interpreter( diff --git a/compiler/qsc_circuit/src/builder.rs b/compiler/qsc_circuit/src/builder.rs index 0df85ba17f..ebc491ebf1 100644 --- a/compiler/qsc_circuit/src/builder.rs +++ b/compiler/qsc_circuit/src/builder.rs @@ -59,8 +59,6 @@ impl Backend for Builder { let mapped_q = self.map(q); // In the Circuit schema, result id is per-qubit let res_id = self.num_measurements_for_qubit(mapped_q); - // We don't actually need the Remapper since we're not - // remapping any qubits, but it's handy for keeping track of measurements let id = self.remapper.m(q); self.push_gate(measurement_gate(mapped_q.0, res_id)); @@ -249,21 +247,6 @@ impl Builder { self.circuit.operations.push(gate); } - fn num_measurements_by_qubit(&self) -> IndexMap { - self.remapper.qubit_measurement_counts.iter().fold( - IndexMap::default(), - |mut map: IndexMap, (q, _)| { - match map.get_mut(q.0) { - Some(rs) => *rs += 1, - None => { - map.insert(q.0, 1); - } - } - map - }, - ) - } - fn num_measurements_for_qubit(&self, qubit: WireId) -> usize { self.remapper .qubit_measurement_counts @@ -273,19 +256,17 @@ impl Builder { } fn finish_circuit(&self, mut circuit: Circuit) -> Circuit { - let by_qubit = self.num_measurements_by_qubit(); - // add deferred measurements if self.config.base_profile { - for (qubit, _) in &by_qubit { + for (qubit, _) in &self.remapper.qubit_measurement_counts { // guaranteed one measurement per qubit, so result is always 0 - circuit.operations.push(measurement_gate(qubit, 0)); + circuit.operations.push(measurement_gate(qubit.0, 0)); } } // add qubit declarations for i in 0..self.remapper.num_qubits() { - let num_measurements = by_qubit.get(i).map_or(0, |c| *c); + let num_measurements = self.num_measurements_for_qubit(WireId(i)); circuit.qubits.push(crate::circuit::Qubit { id: i, num_children: num_measurements,