Release Notes

0.4.0

New Features

• The PySCFGroundStateSolver now also computes the magnetization ($S^z$) and total angular momentum ($S^2$) values for all computes roots. In doing so, it properly takes the alpha-beta overlap matrix from the qiskit_nature.second_q.properties.AngularMomentum.overlap property into account. When this overlap is non-unitary, the spin-contamination within the active subspace is computed correctly. For more details, see also:

  • <https://github.com/qiskit-community/qiskit-nature/issues/1273>_

  • <https://github.com/qiskit-community/qiskit-nature/pull/1275>_

  • <https://github.com/qiskit-community/qiskit-nature/issues/1291>_

  • <https://github.com/qiskit-community/qiskit-nature/pull/1292>_

• Added support for Python 3.12.

0.3.0

Prelude

The use of the deprecated qiskit.algorithms module has been replaced by the new qiskit-algorithms package which provide a drop-in replacement in the form of the qiskit_algorithms module.

New Features

• Support was added for FCISolver instances which have their nroots attribute set to a value higher than 1, indicating that they also compute excited states.

Upgrade Notes

• Support for running with Python 3.7 has been removed. You now need to use Python 3.8 as the minimum version.

Bug Fixes

• The ElectronicDensity object that was returned as part of the ElectronicStructureResult from the PySCFGroundStateSolver was faultily storing restricted-spin information within the alpha-spin register even though the object is documented as storing unrestricted spin-data. This has been fixed and the ElectronicDensity object is now guaranteed to store unrestricted-spin information. If a restricted-spin density is required it may be obtained from the trace_spin() method.

0.2.0

New Features

• Adds the PySCFGroundStateSolver to provide simpler means for testing and debugging classical computational workflows in Qiskit Nature. Below is an example of how to use it:

  from pyscf import fci
  
  from qiskit_nature.second_q.drivers import MethodType, PySCFDriver
  from qiskit_nature.second_q.transformers import ActiveSpaceTransformer
  
  from qiskit_nature_pyscf import PySCFGroundStateSolver
  
  driver = PySCFDriver(
      atom="O 0.0 0.0 0.0; O 0.0 0.0 1.5",
      basis="sto3g",
      spin=2,
      method=MethodType.UHF,
  )
  problem = driver.run()
  
  transformer = ActiveSpaceTransformer(4, 4)
  
  problem = transformer.transform(problem)
  
  solver = PySCFGroundStateSolver(fci.direct_uhf.FCI())
  
  result = solver.solve(problem)
  print(result)
  

• Added support for running with Python 3.11.

Bug Fixes

• Ensures compatibility of this plugin with Qiskit Nature 0.6. The examples are updated in order to avoid triggering deprecation warnings. Using Qiskit Nature 0.5 is still supported.

0.1.0

New Features

• First release of Qiskit Nature PySCF with the class qiskit_nature_pyscf.runtime.QiskitSolver

  from pyscf import gto, scf, mcscf
  
  from qiskit.algorithms.optimizers import SLSQP
  from qiskit.primitives import Estimator
  from qiskit_nature.second_q.algorithms import GroundStateEigensolver, VQEUCCFactory
  from qiskit_nature.second_q.circuit.library import UCCSD
  from qiskit_nature.second_q.mappers import ParityMapper, QubitConverter
  
  from qiskit_nature_pyscf import QiskitSolver
  
  mol = gto.M(atom="Li 0 0 0; H 0 0 1.6", basis="sto-3g")
  
  h_f = scf.RHF(mol).run()
  
  norb, nelec = 2, 2
  
  cas = mcscf.CASCI(h_f, norb, nelec)
  
  converter = QubitConverter(ParityMapper(), two_qubit_reduction=True)
  
  vqe = VQEUCCFactory(Estimator(), UCCSD(), SLSQP())
  
  algorithm = GroundStateEigensolver(converter, vqe)
  
  cas.fcisolver = QiskitSolver(algorithm)
  
  cas.run()