[Test] Add three qubit gate tests for density matrix.

Author: Zhuoyang Ye

test/density/test_density_op.py

@@ -132,7 +132,7 @@ def density_is_close(mat1: np.ndarray, mat2: np.ndarray):
 
 
 
-class single_qubit(TestCase):
+class single_qubit_test(TestCase):
     def compare_single_gate(self, gate_pair, qubit_num):
         passed = True
         for index in range(0, qubit_num):
@@ -157,7 +157,7 @@ def test_single_gates(self):
 
 
 
-class Two_qubit(TestCase):
+class two_qubit_test(TestCase):
     def compare_two_qubit_gate(self, gate_pair, qubit_num):
         passed = True
         for index1 in range(0, qubit_num):
@@ -184,5 +184,34 @@ def test_two_qubits_gates(self):
             self.assertTrue(self.compare_two_qubit_gate(two_qubit_gate_list[i], 5))
 
 
+class three_qubit_test(TestCase):
+    def compare_three_qubit_gate(self, gate_pair, qubit_num):
+        passed = True
+        for index1 in range(0, qubit_num):
+            for index2 in range(0, qubit_num):
+                if (index1 == index2):
+                    continue
+                for index3 in range(0, qubit_num):
+                    if (index3 == index1) or (index3 == index2):
+                        continue
+                    qdev = tq.NoiseDevice(n_wires=qubit_num, bsz=1, device="cpu", record_op=True)
+                    gate_pair['tq'](qdev, [index1,index2,index3])
+                    mat1 = np.array(qdev.get_2d_matrix(0))
+                    rho_qiskit = qiskitDensity.from_label('0' * qubit_num)
+                    rho_qiskit = rho_qiskit.evolve(gate_pair['qiskit'](), [qubit_num - 1 - index1,qubit_num - 1 - index2,qubit_num - 1 - index3])
+                    mat2 = np.array(rho_qiskit.to_operator())
+                    if density_is_close(mat1, mat2):
+                        print("Test passed for %s gate on qubit (%d,%d,%d) when qubit_number is %d!" % (
+                        gate_pair['name'], index1,index2,index3, qubit_num))
+                    else:
+                        passed = False
+                        print("Test failed for %s gate on qubit (%d,%d,%d)  when qubit_number is %d!" % (
+                        gate_pair['name'], index1,index2,index3,qubit_num))
+        return passed
+
+    def test_three_qubits_gates(self):
+        for i in range(0, len(three_qubit_gate_list)):
+            self.assertTrue(self.compare_three_qubit_gate(three_qubit_gate_list[i], 5))
+