Skip unitary in Clifford check (quantumlib#3165)

Fixes quantumlib#3164.
zaqqwerty · Jul 22, 2020 · 7a4ccaf · 7a4ccaf
1 parent 0952958
commit 7a4ccaf
Showing 1 changed file with 3 additions and 3 deletions.
diff --git a/cirq/sim/clifford/clifford_simulator.py b/cirq/sim/clifford/clifford_simulator.py
@@ -66,9 +66,9 @@ def is_supported_operation(op: 'cirq.Operation') -> bool:
         if isinstance(op.gate, cirq.MeasurementGate): return True
         if isinstance(op, GlobalPhaseOperation): return True
         if not protocols.has_unitary(op): return False
-        u = unitary(op)
-        if u.shape == (2, 2):
-            return not SingleQubitCliffordGate.from_unitary(u) is None
+        if len(op.qubits) == 1:
+            u = unitary(op)
+            return SingleQubitCliffordGate.from_unitary(u) is not None
         else:
             return op.gate in [cirq.CNOT, cirq.CZ]