Add CliffordCircuitPredicate if we're using the stabilizer simulator (#560)

Author: isobelhooper

docs/changelog.md

@@ -4,6 +4,11 @@
 
 # Changelog
 
+## Unreleased
+
+- Add CliffordCircuitPredicate for circuit compilation and processing
+  when using the stabilizer simulator.
+
 ## 0.44.0 (February 2025)
 
 - Remove `noise_specs` from local-emulator backends.

pytket/extensions/quantinuum/backends/quantinuum.py

@@ -65,6 +65,7 @@
     scratch_reg_resize_pass,
 )
 from pytket.predicates import (
+    CliffordCircuitPredicate,
     GateSetPredicate,
     MaxNClRegPredicate,
     MaxNQubitsPredicate,
@@ -621,6 +622,8 @@ def required_predicates(self) -> list[Predicate]:
             assert self.backend_info is not None
             preds.append(MaxNQubitsPredicate(self.backend_info.n_nodes))
             preds.append(MaxNClRegPredicate(cast(int, self.backend_info.n_cl_reg)))
+        if self.simulator_type == "stabilizer":
+            preds.append(CliffordCircuitPredicate())
 
         return preds
 

tests/integration/backend_test.py

@@ -56,7 +56,7 @@
     QuantinuumAPI,
     QuantinuumAPIError,
 )
-from pytket.extensions.quantinuum.backends.quantinuum import _ALL_GATES, GetResultFailed
+from pytket.extensions.quantinuum.backends.quantinuum import _ALL_GATES
 from pytket.predicates import CompilationUnit
 from pytket.wasm import WasmFileHandler
 
@@ -530,11 +530,11 @@ def test_leakage_detection(
 
 
 @given(
-    n_shots=st.integers(min_value=1, max_value=10),  # type: ignore
+    n_shots=st.integers(min_value=1, max_value=10),
     n_bits=st.integers(min_value=0, max_value=10),
 )
 @pytest.mark.timeout(120)
-def test_shots_bits_edgecases(n_shots, n_bits) -> None:
+def test_shots_bits_edgecases(n_shots: int, n_bits: int) -> None:
     quantinuum_backend = QuantinuumBackend("H1-1SC", machine_debug=True)
     c = Circuit(n_bits, n_bits)
 
@@ -597,18 +597,17 @@ def test_simulator(
     assert sum(stab_counts.values()) == n_shots
     assert len(stab_counts) == 2
 
-    # test non-clifford circuit fails on stabilizer backend
-    # unfortunately the job is accepted, then fails, so have to check get_result
+    # test non-clifford circuit fails predicate check
+    # when run on stabilizer backend
     non_stab_circ = (
         Circuit(2, name="non_stab_circ").H(0).Rx(0.1, 0).CX(0, 1).measure_all()
     )
     non_stab_circ = stabilizer_backend.get_compiled_circuit(non_stab_circ)
-    broken_handle = stabilizer_backend.process_circuit(
-        non_stab_circ, n_shots, language=language
-    )
 
-    with pytest.raises(GetResultFailed) as _:
-        _ = stabilizer_backend.get_result(broken_handle)
+    with pytest.raises(CircuitNotValidError):
+        _ = stabilizer_backend.process_circuit(
+            non_stab_circ, n_shots, noisy_simulation=False, language=language
+        )
 
 
 @pytest.mark.skipif(skip_remote_tests, reason=REASON)

tests/unit/backend.py

@@ -0,0 +1,29 @@
+import pytest
+
+from pytket.extensions.quantinuum import QuantinuumAPIOffline, QuantinuumBackend
+from pytket.predicates import CliffordCircuitPredicate
+
+
+@pytest.mark.parametrize(
+    "simulator_type,should_have_clifford_predicate",
+    [
+        ("state-vector", False),
+        ("stabilizer", True),
+    ],
+)
+def test_clifford_circuits_for_stabilizer(
+    simulator_type: str,
+    should_have_clifford_predicate: bool,
+) -> None:
+    """Check that the stabilizer simulator restricts circuits to be Clifford circuits,
+    and the statevector simulator does not."""
+    qapi_offline = QuantinuumAPIOffline()
+    backend = QuantinuumBackend(
+        "H1-1E",
+        api_handler=qapi_offline,  # type: ignore
+        simulator=simulator_type,
+    )
+    required_predicates = backend.required_predicates
+    assert should_have_clifford_predicate == any(
+        isinstance(pred, CliffordCircuitPredicate) for pred in required_predicates
+    )

tests/unit/offline_backend_test.py

@@ -117,7 +117,7 @@ def test_tket_pass_submission(language: Language) -> None:
 
 
 @given(
-    n_shots=strategies.integers(min_value=1, max_value=10),  # type: ignore
+    n_shots=strategies.integers(min_value=1, max_value=10),
     n_bits=strategies.integers(min_value=0, max_value=10),
 )
 @pytest.mark.parametrize(
@@ -128,7 +128,7 @@ def test_tket_pass_submission(language: Language) -> None:
         Language.PQIR,
     ],
 )
-def test_shots_bits_edgecases(n_shots, n_bits, language: Language) -> None:
+def test_shots_bits_edgecases(n_shots: int, n_bits: int, language: Language) -> None:
     quantinuum_backend = QuantinuumBackend("H1-1SC", machine_debug=True)
     c = Circuit(n_bits, n_bits)