Merge pull request #269 from rafaelha/master

Bug fix in simplify.to_clifford_normal_form_graph

pyzx/simplify.py

@@ -546,9 +546,10 @@ def to_clifford_normal_form_graph(g: BaseGraph[VT,ET]) -> None:
         v = v_inputs[q]
         i = inputs[q]
         e = g.edge(v,i)
-        if g.edge_type(e) == EdgeType.HADAMARD or g.phase(v) != 0:
+        e_type = g.edge_type(e)
+        if e_type == EdgeType.HADAMARD or g.phase(v) != 0:
             h = g.add_vertex(VertexType.Z, q, row=1, phase=g.phase(v))
-            g.add_edge((i,h),EdgeType.HADAMARD)
+            g.add_edge((i,h),e_type)
             g.add_edge((h,v),EdgeType.SIMPLE)
             g.remove_edge(e)
             g.set_phase(v,0)
@@ -558,9 +559,10 @@ def to_clifford_normal_form_graph(g: BaseGraph[VT,ET]) -> None:
         v = v_outputs[q]
         o = outputs[q]
         e = g.edge(v,o)
-        if g.edge_type(e) == EdgeType.HADAMARD or g.phase(v) != 0:
+        e_type = g.edge_type(e)
+        if e_type == EdgeType.HADAMARD or g.phase(v) != 0:
             h = g.add_vertex(VertexType.Z, q, row=7, phase=g.phase(v))
-            g.add_edge((h,o),EdgeType.HADAMARD)
+            g.add_edge((h,o),e_type)
             g.add_edge((v,h),EdgeType.SIMPLE)
             g.remove_edge(e)
             g.set_phase(v,0)

tests/test_simplify.py

@@ -32,7 +32,9 @@
 from fractions import Fraction
 from pyzx.generate import cliffordT
 from pyzx.simplify import *
-from pyzx.simplify import supplementarity_simp
+from pyzx.simplify import supplementarity_simp, to_clifford_normal_form_graph
+from pyzx import compare_tensors
+from pyzx.generate import cliffordT
 
 np: Optional[ModuleType]
 try:
@@ -130,6 +132,13 @@ def test_full_reduce_with_h_box(self):
             full_reduce(g)
         self.assertTrue("Input graph is not a ZX-diagram" in str(context.exception))
 
+    def test_to_clifford_normal_form_graph(self):
+        for _ in range(10):
+            g = cliffordT(4, 20, p_t=0)
+            g0 = g.copy()
+            to_clifford_normal_form_graph(g)
+            self.assertTrue(compare_tensors(g0, g, preserve_scalar=True))
+
 
 qasm_1 = """OPENQASM 2.0;
 include "qelib1.inc";