Fix a bug with Barrier not being supported in Azure-qiskit

CHANGELOG.md

@@ -7,6 +7,11 @@
 * Updated qiskit ecosystem versions: qiskit to 2.3.0 and qiskit-ibm-runtime to 0.45.0.
   [(#681)](https://github.com/PennyLaneAI/pennylane-qiskit/pull/681)
 
+* The circuit conversion from PennyLane no longer inserts a superfluous `barrier` to 
+  delineate the circuit operations from the terminal measurements. This will allow support 
+  for remote backends that don't support `barrier`.
+  [(#677)](https://github.com/PennyLaneAI/pennylane-qiskit/pull/677)
+
 ### Breaking changes 💔
 
 ### Deprecations 👋

pennylane_qiskit/aer.py

@@ -16,6 +16,7 @@
 evaluation and differentiation of Qiskit Aer's C++ simulator
 using PennyLane.
 """
+
 import qiskit_aer
 
 from .qiskit_device_legacy import QiskitDeviceLegacy

pennylane_qiskit/basic_sim.py

@@ -16,6 +16,7 @@
 evaluation and differentiation of Qiskit Terra's BasicAer simulator
 using PennyLane.
 """
+
 from qiskit.providers.basic_provider import BasicProvider
 
 from .qiskit_device_legacy import QiskitDeviceLegacy

pennylane_qiskit/converter.py

@@ -15,6 +15,7 @@
 This module contains functions for converting between Qiskit QuantumCircuit objects
 and PennyLane circuits.
 """
+
 import warnings
 from collections.abc import Iterable, Sequence
 from functools import partial, reduce
@@ -501,7 +502,7 @@ def _function(*args, params: dict = None, wires: list = None, **kwargs):
         # Processing the dictionary of parameters passed
         # pylint: disable=too-many-nested-blocks
         for idx, circuit_instruction in enumerate(qc.data):
-            (instruction, qargs, cargs) = (
+            instruction, qargs, cargs = (
                 circuit_instruction.operation,
                 circuit_instruction.qubits,
                 circuit_instruction.clbits,
@@ -712,8 +713,6 @@ def circuit_to_qiskit(circuit, register_size, diagonalize=True, measure=True):
         for rot in rotations:
             qc &= operation_to_qiskit(rot, reg, creg)
 
-    # barrier ensures we first do all operations, then do all measurements
-    qc.barrier(reg)
     # we always measure the full register
     qc.measure(reg, creg)
 

pennylane_qiskit/noise_models.py

@@ -15,6 +15,7 @@
 This module contains functions for converting Qiskit NoiseModel objects
 into PennyLane NoiseModels.
 """
+
 from collections import defaultdict
 from warnings import warn
 

pennylane_qiskit/qiskit_device.py

@@ -15,6 +15,7 @@
 This module contains a prototype base class for constructing Qiskit devices
 for PennyLane with the new device API.
 """
+
 # pylint: disable=too-many-instance-attributes,attribute-defined-outside-init,too-many-positional-arguments
 
 import inspect

pennylane_qiskit/qiskit_device_legacy.py

@@ -14,6 +14,7 @@
 r"""
 This module contains a base class for constructing Qiskit devices for PennyLane.
 """
+
 # pylint: disable=too-many-instance-attributes,attribute-defined-outside-init
 
 

tests/test_apply.py

@@ -14,6 +14,7 @@
 r"""
 This module contains tests for applying operations on PennyLane IBMQ devices.
 """
+
 import numpy as np
 import pennylane as qml
 

tests/test_base_device.py

@@ -14,6 +14,7 @@
 """
 This module contains tests for the base Qiskit device for the new PennyLane device API
 """
+
 # pylint: disable=too-many-positional-arguments
 
 from unittest.mock import Mock, patch

tests/test_converter.py

@@ -14,6 +14,7 @@
 r"""
 This module contains tests for converting circuits for PennyLane IBMQ devices.
 """
+
 import functools as ft
 import itertools as it
 
@@ -1722,10 +1723,10 @@ def test_circuit_to_qiskit_diagonalize_kwarg(self, diagonalize):
 
         qc = circuit_to_qiskit(qscript, 2, diagonalize=diagonalize, measure=True)
 
-        # get list of instruction names up to the barrier (played right before measurements)
+        # get list of instruction names up to the first measurement
         instructions = []
         for instruction in qc.data:
-            if instruction.operation.name == "barrier":
+            if instruction.operation.name == "measure":
                 break
             instructions.append(instruction.operation.name)
 
@@ -1745,10 +1746,10 @@ def test_circuit_to_qiskit_measurements_with_overlapping_wires(self):
 
         qc = circuit_to_qiskit(tape, 2, diagonalize=True, measure=True)
 
-        # get list of instruction names up to the barrier (played right before measurements)
+        # get list of instruction names up to the first measurement
         instructions = []
         for instruction in qc.data:
-            if instruction.operation.name == "barrier":
+            if instruction.operation.name == "measure":
                 break
             instructions.append(instruction.operation.name)
 

tests/test_expval.py

@@ -14,6 +14,7 @@
 r"""
 This module contains tests for using expvals for PennyLane IBMQ devices.
 """
+
 import numpy as np
 import pennylane as qml
 

tests/test_integration.py

@@ -14,6 +14,7 @@
 r"""
 This module contains integration tests for PennyLane IBMQ devices.
 """
+
 # pylint: disable=too-many-positional-arguments
 import sys
 from functools import partial

tests/test_inverses.py

@@ -14,6 +14,7 @@
 r"""
 This module contains tests for using adjoints for PennyLane IBMQ devices.
 """
+
 import cmath
 import math
 

tests/test_noise_models.py

@@ -14,6 +14,7 @@
 r"""
 This module contains tests for converting Qiskit NoiseModels to PennyLane NoiseModels.
 """
+
 import itertools as it
 from functools import reduce
 

tests/test_qiskit_device.py

@@ -14,6 +14,7 @@
 r"""
 This module contains tests qiskit devices for PennyLane IBMQ devices.
 """
+
 from unittest.mock import Mock
 
 import numpy as np

tests/test_var.py

@@ -14,6 +14,7 @@
 r"""
 This module contains tests for computing variances on PennyLane IBMQ devices.
 """
+
 import numpy as np
 import pennylane as qml