Merge pull request #168 from BoxiLi/chain_strucuture_bug

Fix bugs in to_chain_structure

src/qutip_qip/transpiler/chain.py

@@ -1,3 +1,4 @@
+from copy import deepcopy
 from ..circuit import QubitCircuit
 
 
@@ -27,7 +28,8 @@ def to_chain_structure(qc, setup="linear"):
     # FIXME This huge block has been here for a long time.
     # It could be moved to the new compiler section and carefully
     # splitted into smaller peaces.
-    qc_t = QubitCircuit(qc.N, qc.reverse_states)
+    qc_t = deepcopy(qc)
+    qc_t.gates = []
     swap_gates = [
         "SWAP",
         "ISWAP",
@@ -263,12 +265,8 @@ def to_chain_structure(qc, setup="linear"):
                     j = j + 1
 
         else:
-            qc_t.add_gate(
-                gate.name,
-                gate.targets,
-                gate.controls,
-                gate.arg_value,
-                gate.arg_label,
-            )
+            # This gate can be general quantum operations
+            # such as measurement or global phase.
+            qc_t.add_gate(gate)
 
     return qc_t

tests/test_circuit.py

@@ -12,7 +12,7 @@
 from qutip_qip.operations import (
     Gate, gates, Measurement, gate_sequence_product
 )
-
+from qutip_qip.transpiler import to_chain_structure
 from qutip_qip.decompose.decompose_single_qubit_gate import _ZYZ_rotation
 
 import qutip as qp
@@ -763,3 +763,14 @@ def test_deprecation_warning(self):
         with pytest.warns(DeprecationWarning):
             from qutip_qip.circuit import Gate, Measurement
             Gate("X", 0)
+
+    def test_circuit_chain_structure(self):
+        """
+        Test if the transpiler correctly inherit the properties of a circuit.
+        """
+        qc = QubitCircuit(3, reverse_states=True)
+        qc.add_gate("CNOT", 2, 0)
+        qc2 = to_chain_structure(qc)
+
+        assert qc2.reverse_states is True
+        assert qc2.input_states == [None] * 3