exposing stabilizer seeding for the Python wrappers (#275)

Author: ciaranra

.github/dependabot.yml

@@ -0,0 +1,48 @@
+version: 2
+
+updates:
+  # Rust (Cargo) - security updates only
+  - package-ecosystem: "cargo"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+    open-pull-requests-limit: 5
+    groups:
+      rust-security:
+        applies-to: security-updates
+        patterns: ["*"]
+    # Only open PRs for security advisories
+    allow:
+      - dependency-type: "all"
+    # Ignore all version updates (non-security)
+    ignore:
+      - dependency-name: "*"
+        update-types: ["version-update:semver-patch", "version-update:semver-minor", "version-update:semver-major"]
+
+  # Python (pip) - security updates only
+  - package-ecosystem: "pip"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+    open-pull-requests-limit: 5
+    groups:
+      python-security:
+        applies-to: security-updates
+        patterns: ["*"]
+    ignore:
+      - dependency-name: "*"
+        update-types: ["version-update:semver-patch", "version-update:semver-minor", "version-update:semver-major"]
+
+  # GitHub Actions - security updates only
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+    open-pull-requests-limit: 5
+    groups:
+      actions-security:
+        applies-to: security-updates
+        patterns: ["*"]
+    ignore:
+      - dependency-name: "*"
+        update-types: ["version-update:semver-patch", "version-update:semver-minor", "version-update:semver-major"]

Cargo.lock

@@ -771,7 +771,8 @@ class GateBindingsDict:
 class SparseSim:
     """Sparse stabilizer simulator."""
 
-    def __init__(self, num_qubits: int) -> None: ...
+    def __init__(self, num_qubits: int, seed: int | None = None) -> None: ...
+    def set_seed(self, seed: int) -> None: ...
     def reset(self) -> SparseSim: ...
     @property
     def num_qubits(self) -> int: ...
@@ -788,7 +789,8 @@ class SparseSim:
 class Stab:
     """Generic stabilizer simulator (recommended)."""
 
-    def __init__(self, num_qubits: int) -> None: ...
+    def __init__(self, num_qubits: int, seed: int | None = None) -> None: ...
+    def set_seed(self, seed: int) -> None: ...
     def reset(self) -> Stab: ...
     @property
     def num_qubits(self) -> int: ...

python/pecos-rslib/pecos_rslib.pyi

@@ -24,12 +24,20 @@ pub struct PySparseSim {
 #[pymethods]
 impl PySparseSim {
     #[new]
-    fn new(num_qubits: usize) -> Self {
+    #[pyo3(signature = (num_qubits, seed=None))]
+    fn new(num_qubits: usize, seed: Option<u64>) -> Self {
         PySparseSim {
-            inner: SparseStab::new(num_qubits),
+            inner: match seed {
+                Some(s) => SparseStab::with_seed(num_qubits, s),
+                None => SparseStab::new(num_qubits),
+            },
         }
     }
 
+    fn set_seed(&mut self, seed: u64) {
+        self.inner.set_seed(seed);
+    }
+
     fn reset(mut slf: PyRefMut<'_, Self>) -> PyRefMut<'_, Self> {
         slf.inner.reset();
         slf

python/pecos-rslib/src/sparse_stab_bindings.rs

@@ -24,12 +24,20 @@ pub struct PyStab {
 #[pymethods]
 impl PyStab {
     #[new]
-    fn new(num_qubits: usize) -> Self {
+    #[pyo3(signature = (num_qubits, seed=None))]
+    fn new(num_qubits: usize, seed: Option<u64>) -> Self {
         PyStab {
-            inner: Stab::new(num_qubits),
+            inner: match seed {
+                Some(s) => Stab::with_seed(num_qubits, s),
+                None => Stab::new(num_qubits),
+            },
         }
     }
 
+    fn set_seed(&mut self, seed: u64) {
+        self.inner.set_seed(seed);
+    }
+
     fn reset(mut slf: PyRefMut<'_, Self>) -> PyRefMut<'_, Self> {
         slf.inner.reset();
         slf

python/pecos-rslib/src/stab_bindings.rs

@@ -0,0 +1,52 @@
+# Copyright 2026 The PECOS Developers
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
+# in compliance with the License. You may obtain a copy of the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software distributed under the License
+# is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
+# or implied. See the License for the specific language governing permissions and limitations under
+# the License.
+
+"""Tests for simulator seeding via the pecos_rslib bindings."""
+
+import pytest
+from pecos_rslib.simulators import SparseSim, Stab
+
+
+def _measure_sequence(sim_cls: type, *, seed: int, rounds: int = 16) -> list:
+    """Create a seeded simulator, apply H then MZ repeatedly, return outcomes."""
+    sim = sim_cls(1, seed=seed)
+    outcomes = []
+    for _ in range(rounds):
+        sim.reset()
+        sim.run_1q_gate("H", 0)
+        outcomes.append(sim.run_1q_gate("MZ", 0))
+    return outcomes
+
+
+@pytest.mark.parametrize("sim_cls", [SparseSim, Stab])
+class TestSimulatorSeeding:
+    """Verify that seeded stabilizer simulators produce reproducible results."""
+
+    def test_constructor_seed_is_reproducible(self, sim_cls: type) -> None:
+        """Same seed in constructor gives same measurement sequence."""
+        assert _measure_sequence(sim_cls, seed=42) == _measure_sequence(sim_cls, seed=42)
+
+    def test_different_seeds_differ(self, sim_cls: type) -> None:
+        """Different seeds give different measurement sequences."""
+        assert _measure_sequence(sim_cls, seed=42) != _measure_sequence(sim_cls, seed=99)
+
+    def test_set_seed_is_reproducible(self, sim_cls: type) -> None:
+        """Calling set_seed after construction gives reproducible results."""
+        sim_a = sim_cls(1)
+        sim_a.set_seed(42)
+        outcomes_a = [sim_a.run_1q_gate("H", 0) for _ in range(8)]
+
+        sim_b = sim_cls(1)
+        sim_b.set_seed(42)
+        outcomes_b = [sim_b.run_1q_gate("H", 0) for _ in range(8)]
+
+        assert outcomes_a == outcomes_b

python/pecos-rslib/tests/test_simulator_seeding.py

@@ -0,0 +1,42 @@
+# Copyright 2026 The PECOS Developers
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
+# in compliance with the License. You may obtain a copy of the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software distributed under the License
+# is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
+# or implied. See the License for the specific language governing permissions and limitations under
+# the License.
+
+"""High-level tests for seeded stabilizer simulator re-exports."""
+
+import pytest
+from pecos.simulators import SparseSim, Stab
+
+
+def _measurement_sequence(
+    sim_cls: type,
+    *,
+    seed: int | None = None,
+    reseed: int | None = None,
+    rounds: int = 16,
+) -> list:
+    sim = sim_cls(1, seed=seed) if seed is not None else sim_cls(1)
+    if reseed is not None:
+        sim.set_seed(reseed)
+
+    outcomes = []
+    for _ in range(rounds):
+        sim.reset()
+        sim.run_1q_gate("H", 0)
+        outcomes.append(sim.run_1q_gate("MZ", 0))
+    return outcomes
+
+
+@pytest.mark.parametrize("sim_cls", [SparseSim, Stab])
+def test_high_level_simulators_accept_seed_and_set_seed(sim_cls: type) -> None:
+    """Verify that seeded stabilizer simulators produce reproducible results."""
+    assert _measurement_sequence(sim_cls, seed=42) == _measurement_sequence(sim_cls, seed=42)
+    assert _measurement_sequence(sim_cls, reseed=42) == _measurement_sequence(sim_cls, reseed=42)