Qiskit · SaashaJoshi · Jun 19, 2023 · May 31, 2023 · Jun 1, 2023 · Jun 1, 2023
diff --git a/README.md b/README.md
@@ -5,7 +5,7 @@
   ![Platform](https://img.shields.io/badge/Platform-Linux%20%7C%20macOS%20%7C%20Windows-informational)
   [![Python](https://img.shields.io/badge/Python-3.8%20%7C%203.9%20%7C%203.10%20%7C%203.11-informational)](https://www.python.org/)
   [![Qiskit](https://img.shields.io/badge/Qiskit-%E2%89%A5%200.43.0-6133BD)](https://github.com/Qiskit/qiskit)
-  [![Qiskit Nature](https://img.shields.io/badge/Qiskit%20Nature-%E2%89%A5%200.5.2-6133BD)](https://github.com/Qiskit/qiskit-nature)
+  [![Qiskit Nature](https://img.shields.io/badge/Qiskit%20Nature-%E2%89%A5%200.6.0-6133BD)](https://github.com/Qiskit/qiskit-nature)
 <br />
   [![DOI](https://zenodo.org/badge/543181258.svg)](https://zenodo.org/badge/latestdoi/543181258)
   [![License](https://img.shields.io/github/license/Qiskit-Extensions/circuit-knitting-toolbox?label=License)](LICENSE.txt)

diff --git a/circuit_knitting/forging/__init__.py b/circuit_knitting/forging/__init__.py
@@ -45,6 +45,16 @@
     EntanglementForgingGroundStateSolver,
 )
 from .cholesky_decomposition import cholesky_decomposition, convert_cholesky_operator
+from qiskit_nature import settings
+
+# From now forward, the entanglement forging module requires that SparsePauliOp
+# be used rather than PauliSumOp, as the latter is deprecated in Qiskit Terra 0.24.
+# However, Qiskit Nature still is not expected to change this default until Qiskit
+# Nature 0.7. Here, we modify the global state to opt into the new behavior early.
+# Unfortunately, this means that any code that calls Qiskit Nature in the same
+# process as entanglement forging will need to be updated to use SparsePauliOp as well.
+
+settings.use_pauli_sum_op = False
 
 __all__ = [
     "EntanglementForgingAnsatz",

diff --git a/circuit_knitting/forging/cholesky_decomposition.py b/circuit_knitting/forging/cholesky_decomposition.py
@@ -18,10 +18,10 @@
 
 import numpy as np
 
-from qiskit.opflow import PauliSumOp
 from qiskit.quantum_info import Pauli
+from qiskit.quantum_info import SparsePauliOp
 from qiskit_nature.second_q.problems import ElectronicStructureProblem
-from qiskit_nature.second_q.mappers import QubitConverter, JordanWignerMapper
+from qiskit_nature.second_q.mappers import JordanWignerMapper
 from qiskit_nature.second_q.operators import (
     FermionicOp,
     PolynomialTensor,
@@ -36,8 +36,8 @@
 
 
 def get_cholesky_op(
-    l_op: np.ndarray, g: int, converter: QubitConverter, opname: str
-) -> PauliSumOp:
+    l_op: np.ndarray, g: int, converter: JordanWignerMapper, opname: str
+) -> SparsePauliOp:
     """
     Convert a two-body term into a cholesky operator.
 
@@ -52,7 +52,7 @@ def get_cholesky_op(
     """
     pt = PolynomialTensor({"+-": l_op[:, :, g]})
     fer_op = FermionicOp.from_polynomial_tensor(pt)
-    cholesky_op = converter.convert(fer_op)
+    cholesky_op = converter.map(fer_op)
     cholesky_op._name = opname + "_chol" + str(g)
 
     return cholesky_op
@@ -62,7 +62,7 @@ def cholesky_decomposition(
     problem: ElectronicStructureProblem,
     mo_coeff: np.ndarray | None = None,
     orbitals_to_reduce: Sequence[int] | None = None,
-) -> tuple[list[PauliSumOp], float]:
+) -> tuple[list[SparsePauliOp], float]:
     """
     Construct the decomposed Hamiltonian from an input ``ElectronicStructureProblem``.
 
@@ -124,14 +124,14 @@ def cholesky_decomposition(
 
 
 def convert_cholesky_operator(
-    operator: list[PauliSumOp],
+    operator: list[SparsePauliOp],
     ansatz: EntanglementForgingAnsatz,
 ) -> EntanglementForgingOperator:
     """
-    Convert the Cholesky operator (List[PauliSumOp]) into the entanglement forging format.
+    Convert the Cholesky operator (List[SparsePauliOp]) into the entanglement forging format.
 
     Args:
-        operator: A `List[PauliSumOp]` containing the single-body Hamiltonian followed
+        operator: A `List[SparsePauliOp]` containing the single-body Hamiltonian followed
             by the Cholesky operators
             shape: [single-body hamiltonian, cholesky_0, ..., cholesky_N]
         ansatz: The ansatz for which to compute expectation values of operator. The
@@ -153,11 +153,7 @@ def convert_cholesky_operator(
     tensor_paulis = set()
     superpos_paulis = set()
     paulis_each_op = [
-        {
-            label: weight
-            for label, weight in op.primitive.to_list()
-            if np.abs(weight) > 0
-        }
+        {label: weight for label, weight in op.to_list() if np.abs(weight) > 0}
         for op in [op1] + list(cholesky_ops)
     ]
 
@@ -242,7 +238,7 @@ def _get_fermionic_ops_with_cholesky(
     occupied_orbitals_to_reduce: np.ndarray | None = None,
     virtual_orbitals_to_reduce: np.ndarray | None = None,
     epsilon_cholesky: float = 1e-10,
-) -> tuple[PauliSumOp, list[PauliSumOp], float, np.ndarray, np.ndarray,]:
+) -> tuple[SparsePauliOp, list[SparsePauliOp], float, np.ndarray, np.ndarray,]:
     r"""
     Decompose the Hamiltonian operators into a form appropriate for entanglement forging.
 
@@ -335,11 +331,10 @@ def _get_fermionic_ops_with_cholesky(
     if halve_transformed_h2:
         h2 /= 2  # type: ignore
 
-    converter = QubitConverter(JordanWignerMapper())
+    converter = JordanWignerMapper()
     pt = PolynomialTensor({"+-": h1, "++--": to_physicist_ordering(h2)})
     fer_op = FermionicOp.from_polynomial_tensor(pt)
-    qubit_op = converter.convert(fer_op)
-
+    qubit_op = converter.map(fer_op)
     qubit_op._name = opname + "_onebodyop"
 
     cholesky_ops = [

diff --git a/circuit_knitting/forging/entanglement_forging_ground_state_solver.py b/circuit_knitting/forging/entanglement_forging_ground_state_solver.py
@@ -33,7 +33,7 @@
     ElectronicBasis,
 )
 from qiskit_ibm_runtime import QiskitRuntimeService, Options
-from qiskit.opflow import PauliSumOp
+from qiskit.quantum_info import SparsePauliOp
 
 from .entanglement_forging_ansatz import EntanglementForgingAnsatz
 from .entanglement_forging_knitter import EntanglementForgingKnitter
@@ -363,7 +363,7 @@ def evaluate_eigenvalue(parameters: Sequence[float]) -> float:
     def get_qubit_operators(
         self,
         problem: ElectronicStructureProblem,
-    ) -> list[PauliSumOp]:
+    ) -> list[SparsePauliOp]:
         """Construct decomposed qubit operators from an ``ElectronicStructureProblem``.
 
         Args:

diff --git a/docs/entanglement_forging/tutorials/tutorial_2_forging_with_quantum_serverless.ipynb b/docs/entanglement_forging/tutorials/tutorial_2_forging_with_quantum_serverless.ipynb
@@ -11,7 +11,7 @@
     "\n",
     "See [Tutorial 1](tutorial_1_getting_started.ipynb) for a high-level breakdown of the entanglement forging algorithm, or check out the [explanatory material](../explanation/index.rst) for a more detailed explanation.\n",
     "\n",
-    "<span style=\"color:red\"><i>Quantum Serverless does not support Qiskit Nature 0.6.0 yet. In order to use entanglement forging with quantum serverless, users should use 0.5.2 < Qiskit Nature < 0.6.0. There is an [associated issue in the quantum-serverless repo](https://github.com/Qiskit-Extensions/quantum-serverless/issues/413) to address this.</i></span>"
+    "<span style=\"color:red\"><i>Quantum Serverless does not support Qiskit Nature 0.6.0 yet. In order to use entanglement forging with quantum serverless, users should downgrade to version 0.2 of the Circuit Knitting Toolbox, as it is compatible with Qiskit Nature 0.5.2. There is an [associated issue in the quantum-serverless repo](https://github.com/Qiskit-Extensions/quantum-serverless/issues/413) to address this.</i></span>"
    ]
   },
   {
@@ -497,7 +497,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.8.16"
+   "version": "3.11.3"
   }
  },
  "nbformat": 4,

diff --git a/pyproject.toml b/pyproject.toml
@@ -28,7 +28,7 @@ requires-python = ">=3.8"
 dependencies = [
     "qiskit-aer>=0.12.0",
     "qiskit-terra>=0.24.0",
-    "qiskit-nature>=0.5.2",
+    "qiskit-nature>=0.6.0",
     "qiskit-ibm-runtime>=0.9.2",
 ]
 
@@ -86,7 +86,6 @@ notebook-dependencies = [
     "matplotlib",
     "ipywidgets",
     "pylatexenc",
-    "qiskit-nature<0.6.0",
 ]
 
 [project.urls]

diff --git a/releasenotes/notes/remove-opflow-177bb07ba0e68002.yaml b/releasenotes/notes/remove-opflow-177bb07ba0e68002.yaml
@@ -0,0 +1,8 @@
+---
+upgrade:
+  - |
+    The dependency on the :mod:`qiskit.opflow` module has been removed from entanglement forging.
+    With this change, Qiskit Nature 0.6.0 is now required.
+    However, Qiskit Nature 0.6.0 is incompatible with Quantum Serverless, so users that wish to
+    use entanglement forging with Quantum Serverless must remain on version 0.2 of the Circuit
+    Knitting Toolbox until `issue #108 <https://github.com/Qiskit-Extensions/circuit-knitting-toolbox/issues/108>`__ is resolved.
diff --git a/tools/extremal-python-dependencies.py b/tools/extremal-python-dependencies.py
@@ -21,7 +21,7 @@ def mapfunc_dev(dep):
     """Load the development version(s) of certain Qiskit-related packages"""
     # https://peps.python.org/pep-0440/#direct-references
     return re.sub(
-        r"^(qiskit-(?:terra|ibm-runtime)).*$",
+        r"^(qiskit-(?:terra|nature|ibm-runtime)).*$",
         r"\1 @ git+https://github.com/Qiskit/\1.git",
         dep,
     )

diff --git a/tox.ini b/tox.ini
@@ -37,7 +37,7 @@ extras =
   nbtest
   notebook-dependencies
 commands =
-  pytest --nbmake --nbmake-timeout=3000 {posargs} docs/
+  pytest --nbmake --nbmake-timeout=3000 {posargs} docs/ --ignore=docs/entanglement_forging/tutorials/tutorial_2_forging_with_quantum_serverless.ipynb
 
 [testenv:coverage]
 basepython = python3.10