Add test for projector.

pyqtorch/__init__.py

@@ -24,6 +24,7 @@
     H,
     I,
     N,
+    Proj,
     S,
     SDagger,
     T,

pyqtorch/primitive.py

@@ -80,7 +80,8 @@ class Proj(Primitive):
     def __init__(self, target: int, state: str = "1"):
         if state == "0":
             super().__init__(OPERATIONS_DICT["PROJ0"], target)
-        super()._init__(OPERATIONS_DICT["PROJ1"], target)
+        else:
+            super().__init__(OPERATIONS_DICT["PROJ1"], target)
 
 
 class N(Primitive):

tests/test_digital.py

@@ -35,6 +35,16 @@ def test_N() -> None:
     assert torch.allclose(product_state("1"), pyq.N(0)(product_state("1"), None))
 
 
+def test_projectors() -> None:
+    t0 = torch.tensor([[0.0], [0.0]], dtype=torch.cdouble)
+    t1 = torch.tensor([[1.0], [0.0]], dtype=torch.cdouble)
+    t2 = torch.tensor([[0.0], [1.0]], dtype=torch.cdouble)
+    assert torch.allclose(t1, pyq.Proj(0, "0")(product_state("0")))
+    assert torch.allclose(t0, pyq.Proj(0, "0")(product_state("1")))
+    assert torch.allclose(t2, pyq.Proj(0, "1")(product_state("1")))
+    assert torch.allclose(t0, pyq.Proj(0, "1")(product_state("0")))
+
+
 def test_CNOT_state00_controlqubit_0() -> None:
     result: torch.Tensor = pyq.CNOT(0, 1)(product_state("00"), None)
     assert torch.equal(product_state("00"), result)