add circuit cop

Author: refraction-ray

CHANGELOG.md

@@ -12,6 +12,12 @@
 
 - Add keras3 example showcasing integration with tc
 
+- Add circuit copy method that avoid shallow copy issue `Circuit.copy()`
+
+### Changed
+
+- The static method `BaseCircuit.copy` is renamed as `BaseCircuit.copy_nodes`
+
 ## 0.10.0
 
 ### Added

docs/source/quickstart.rst

@@ -148,6 +148,8 @@ The IR is given as a list, each element is a dict containing information on one
     >>> c.to_qir()
     [{'gate': cnot, 'index': (0, 1), 'name': 'cnot', 'split': None}, {'gate': crx, 'index': (1, 0), 'name': 'crx', 'split': None, 'parameters': {'theta': 0.2}}]
 
+We can also create new copied circuit via ``c.copy()`` which internally utilize the ``qir``.
+
 
 Programming Paradigm
 -------------------------

tensorcircuit/abstractcircuit.py

@@ -1172,6 +1172,11 @@ def append(
         self.__dict__.update(newc.__dict__)
         return self
 
+    def copy(self) -> "AbstractCircuit":
+        qir = self.to_qir()
+        c = type(self).from_qir(qir, self.circuit_param)
+        return c
+
     def expectation(
         self,
         *ops: Tuple[tn.Node, List[int]],

tensorcircuit/basecircuit.py

@@ -81,7 +81,7 @@ def coloring_copied_nodes(
             node.id = getattr(n0, "id", id(n0))
 
     @staticmethod
-    def copy(
+    def copy_nodes(
         nodes: Sequence[tn.Node],
         dangling: Optional[Sequence[tn.Edge]] = None,
         conj: Optional[bool] = False,
@@ -111,7 +111,7 @@ def copy(
     def _copy(
         self, conj: Optional[bool] = False
     ) -> Tuple[List[tn.Node], List[tn.Edge]]:
-        return self.copy(self._nodes, self._front, conj)
+        return self.copy_nodes(self._nodes, self._front, conj)
 
     def apply_general_gate(
         self,
@@ -171,7 +171,7 @@ def apply_general_gate(
                         self._front[index[0]] = n1[0]
                         self._front[index[1]] = n2[1]
                         if self.is_dm:
-                            [n1l, n2l], _ = self.copy([n1, n2], conj=True)
+                            [n1l, n2l], _ = self.copy_nodes([n1, n2], conj=True)
                             n1l[1] ^ self._front[index[0] + nq]
                             n2l[2] ^ self._front[index[1] + nq]
                             self._nodes.append(n1l)
@@ -186,7 +186,7 @@ def apply_general_gate(
                         self._front[index[0]] = n1[0]
                         self._front[index[1]] = n2[1]
                         if self.is_dm:
-                            [n1l, n2l], _ = self.copy([n1, n2], conj=True)
+                            [n1l, n2l], _ = self.copy_nodes([n1, n2], conj=True)
                             n2l[1] ^ self._front[index[0] + nq]
                             n1l[2] ^ self._front[index[1] + nq]
                             self._nodes.append(n1l)
@@ -203,7 +203,7 @@ def apply_general_gate(
                 # gate.id = id(gate)
                 self._nodes.append(gate)
                 if self.is_dm:
-                    lgates, _ = self.copy([gate], conj=True)
+                    lgates, _ = self.copy_nodes([gate], conj=True)
                     lgate = lgates[0]
                     self._nodes.append(lgate)
                 for i, ind in enumerate(index):

tensorcircuit/densitymatrix.py

@@ -86,7 +86,7 @@ def __init__(
                 for i, n in enumerate(mps_nodes):
                     mps_nodes[i].tensor = backend.cast(n.tensor, dtypestr)  # type: ignore
                 mps_edges = mps_inputs.out_edges + mps_inputs.in_edges
-                self._nodes, self._front = self.copy(mps_nodes, mps_edges)
+                self._nodes, self._front = self.copy_nodes(mps_nodes, mps_edges)
                 self.coloring_nodes(self._nodes)
                 self._double_nodes_front()
 
@@ -131,7 +131,7 @@ def __init__(
         self._extra_qir: List[Dict[str, Any]] = []
 
     def _double_nodes_front(self) -> None:
-        lnodes, lfront = self.copy(self._nodes, self._front, conj=True)
+        lnodes, lfront = self.copy_nodes(self._nodes, self._front, conj=True)
         self._front.extend(lfront)
         self._nodes.extend(lnodes)
 

tensorcircuit/results/counts.py

@@ -9,6 +9,8 @@
 Tensor = Any
 ct = Dict[str, int]
 
+# TODO(@refraction-ray): merge_count
+
 
 def reverse_count(count: ct) -> ct:
     ncount = {}

tests/test_circuit.py

@@ -1627,3 +1627,12 @@ def test_general_kraus_with_prob(backend):
     np.testing.assert_allclose(rs[0][1], [0.25, 0.25, 0.5], atol=1e-5)
     np.testing.assert_allclose(rs[1][1], [0.25, 0.25, 0.5], atol=1e-5)
     np.testing.assert_allclose(tc.backend.norm(c.state()), 1, atol=1e-5)
+
+
+@pytest.mark.parametrize("backend", [lf("tfb"), lf("jaxb"), lf("npb")])
+def test_circuit_copy(backend):
+    c = tc.Circuit(2)
+    c.h(0)
+    c1 = c.copy()
+    c.rz(0, theta=0.1)
+    assert c1.gate_count() == 1