factorize inplace while removing qubit in density matrix simulation s…

…tate

cirq-core/cirq/sim/density_matrix_simulation_state.py

@@ -297,10 +297,10 @@ def remove_qubits(self, qubits: Sequence['cirq.Qid']):
         ret = super().remove_qubits(qubits)
         if ret is not NotImplemented:
             return ret
-        extracted, remainder = self.factor(qubits)
+        extracted, remainder = self.factor(qubits, inplace=True)
         remainder._state._density_matrix *= extracted._state._density_matrix.reshape(-1)[0]
         return remainder
-    
+
     def _act_on_fallback_(
         self, action: Any, qubits: Sequence['cirq.Qid'], allow_decompose: bool = True
     ) -> bool:

cirq-core/cirq/sim/simulation_state_test.py

@@ -153,21 +153,7 @@ def test_delegating_gate_unitary(exp):
     assert_test_circuit_for_sv_simulator(test_circuit, control_circuit)
 
 
-@pytest.mark.parametrize('exp', np.linspace(0, 2 * np.pi, 1))
-def test_delegating_gate_channel_sv(exp):
-    q = cirq.LineQubit(0)
-
-    test_circuit = cirq.Circuit()
-    test_circuit.append(cirq.H(q))
-    test_circuit.append(DelegatingAncillaZ(exp, True).on(q))
-
-    control_circuit = cirq.Circuit(cirq.H(q))
-    control_circuit.append(cirq.ZPowGate(exponent=exp).on(q))
-
-    assert_test_circuit_for_sv_simulator(test_circuit, control_circuit)
-
-
-@pytest.mark.parametrize('exp', np.linspace(0, 2 * np.pi, 1))
+@pytest.mark.parametrize('exp', np.linspace(0, 2 * np.pi, 10))
 def test_delegating_gate_channel(exp):
     q = cirq.LineQubit(0)
 
@@ -178,6 +164,7 @@ def test_delegating_gate_channel(exp):
     control_circuit = cirq.Circuit(cirq.H(q))
     control_circuit.append(cirq.ZPowGate(exponent=exp).on(q))
 
+    assert_test_circuit_for_sv_simulator(test_circuit, control_circuit)
     assert_test_circuit_for_dm_simulator(test_circuit, control_circuit)