add keep_measure_order option in from_openqasm method

Author: refraction-ray

CHANGELOG.md

@@ -17,6 +17,8 @@
 
 - Auto unroll composite qiskit instructions when translating to tc circuit
 
+- Add `keep_measure_order` bool option to `from_openqasm` methods so that the measure instruction order is kept by qiskit
+
 ### Fixed
 
 - Fix adjoint possible bug with agnostic backend

tensorcircuit/abstractcircuit.py

@@ -580,21 +580,39 @@ def to_openqasm(self, **kws: Any) -> str:
 
     @classmethod
     def from_openqasm(
-        cls, qasmstr: str, circuit_params: Optional[Dict[str, Any]] = None
+        cls,
+        qasmstr: str,
+        circuit_params: Optional[Dict[str, Any]] = None,
+        keep_measure_order: bool = False,
     ) -> "AbstractCircuit":
         from qiskit.circuit import QuantumCircuit
 
-        qiskit_circ = QuantumCircuit.from_qasm_str(qasmstr)
+        if keep_measure_order is True:
+            from .translation import qiskit_from_qasm_str_ordered_measure
+
+            qiskit_circ = qiskit_from_qasm_str_ordered_measure(qasmstr)
+        else:
+            qiskit_circ = QuantumCircuit.from_qasm_str(qasmstr)
         c = cls.from_qiskit(qiskit_circ, circuit_params=circuit_params)
         return c
 
     @classmethod
     def from_openqasm_file(
-        cls, file: str, circuit_params: Optional[Dict[str, Any]] = None
+        cls,
+        file: str,
+        circuit_params: Optional[Dict[str, Any]] = None,
+        keep_measure_order: bool = False,
     ) -> "AbstractCircuit":
         from qiskit.circuit import QuantumCircuit
 
-        qiskit_circ = QuantumCircuit.from_qasm_file(file)
+        if keep_measure_order is True:
+            from .translation import qiskit_from_qasm_str_ordered_measure
+
+            with open(file) as f:
+                qasmstr = f.read()
+            qiskit_circ = qiskit_from_qasm_str_ordered_measure(qasmstr)
+        else:
+            qiskit_circ = QuantumCircuit.from_qasm_file(file)
         c = cls.from_qiskit(qiskit_circ, circuit_params=circuit_params)
         return c
 

tensorcircuit/quantum.py

@@ -1387,7 +1387,7 @@ def ps2coo_core(
         return tf.SparseTensor(indices=indices, values=values, dense_shape=(s, s))  # type: ignore
 
 except (NameError, ImportError):
-    logger.warning(
+    logger.info(
         "tensorflow is not installed, and sparse Hamiltonian generation utilities are disabled"
     )
 

tensorcircuit/translation.py

@@ -17,7 +17,7 @@
     from qiskit.extensions.exceptions import ExtensionError
 except ImportError:
     logger.warning(
-        "Please first ``pip install -U qiskit`` to enable related functionality"
+        "Please first ``pip install -U qiskit`` to enable related functionality in translation module"
     )
 
 from . import gates
@@ -508,3 +508,31 @@ def eqasm2tc(
                 getattr(c, gate_name)(*index)
 
     return c
+
+
+def qiskit_from_qasm_str_ordered_measure(qasm_str: str) -> Any:
+    """
+    qiskit ``from_qasm_str`` method cannot keep the order of measure as the qasm file,
+    we provide this alternative function in case the order of measure instruction matters
+
+    :param qasm_str: open qasm str
+    :type qasm_str: str
+    :return: ``qiskit.circuit.QuantumCircuit``
+    :rtype: Any
+    """
+    measure_sequence = []
+    qasm_instruction = []
+    for line in qasm_str.split("\n"):
+        if line.startswith("measure"):
+            print(line)
+            index = int(line.split(" ")[1][2:-1])
+            cindex = int(line.split(" ")[3].strip(";")[2:-1])
+
+            measure_sequence.append((index, cindex))
+        else:
+            qasm_instruction.append(line)
+
+    qc = QuantumCircuit.from_qasm_str("\n".join(qasm_instruction))
+    for qid, cid in measure_sequence:
+        qc.measure(qid, cid)
+    return qc

tests/test_circuit.py

@@ -1256,3 +1256,17 @@ def test_to_openqasm():
     c.to_openqasm(filename="test.qasm")
     c2 = tc.Circuit.from_openqasm_file("test.qasm")
     np.testing.assert_allclose(c.state(), c2.state())
+
+
+def test_from_qasm_keep_measure_order():
+    qasm_str = """OPENQASM 2.0;
+include "qelib1.inc";
+qreg q[2];
+creg c[2];
+h q[0];
+measure q[1] -> c[1];
+measure q[0] -> c[0];"""
+    c = tc.Circuit.from_openqasm(qasm_str)
+    c.to_openqasm().split("\n")[-2][-3] == "1"
+    c = tc.Circuit.from_openqasm(qasm_str, keep_measure_order=True)
+    c.to_openqasm().split("\n")[-2][-3] == "0"