Merge pull request #263 from amirebrahimi/fix-cliffordTmeas

Allow generating single qubit Clifford+T circuits

pyzx/generate.py

@@ -288,7 +288,7 @@ def cliffordTmeas(
     else: rest -= p_s
     if p_hsh is None: num += 1.0
     else: rest -= p_hsh
-    if p_cnot is None: num += 1.0
+    if p_cnot is None: num += 1.0 if qubits > 1 else 0.0
     else: rest -= p_cnot
     if p_meas is None: num += 1.0
     else: rest -= p_meas
@@ -298,13 +298,15 @@ def cliffordTmeas(
     if p_t is None: p_t = rest / num
     if p_s is None: p_s = rest / num
     if p_hsh is None: p_hsh = rest / num
-    if p_cnot is None: p_cnot = rest / num
+    if p_cnot is None: p_cnot = rest / num if qubits > 1 else 0.0
     if p_meas is None: p_meas = rest / num
 
+    if p_cnot > 0 and qubits <= 1: raise ValueError("Cannot have p_cnot > 0 with a single qubit.")
+
     #p_s = (1 - p_t) / 3.0
     #p_hsh = (1 - p_t) / 3.0
     #p_cnot = (1 - p_t) / 3.0
-    
+
     inputs = []
     outputs = []
 

tests/test_circuit.py

@@ -83,13 +83,18 @@ def test_load_quipper_from_file(self):
         self.assertListEqual(c2.gates,c2.gates)
 
     def test_cliffordT_preserves_graph_semantics(self):
-        random.seed(SEED)
-        g = cliffordT(4,20,0.2)
-        c = Circuit.from_graph(g)
-        g2 = c.to_graph()
-        t = tensorfy(g,False)
-        t2 = tensorfy(g2,False)
-        self.assertTrue(compare_tensors(t,t2, False))
+        for i in range(1,5):
+            with self.subTest(i):
+                random.seed(SEED)
+                g = cliffordT(i,20,0.2)
+                c = Circuit.from_graph(g)
+                g2 = c.to_graph()
+                t = tensorfy(g,False)
+                t2 = tensorfy(g2,False)
+                self.assertTrue(compare_tensors(t,t2, False))
+
+    def test_cliffordT_raises_exception_with_pcnot(self):
+        self.assertRaises(ValueError, cliffordT, 1, 1, p_cnot=0.1)
 
     def test_cliffords_preserves_graph_semantics(self):
         random.seed(SEED)