I am a student and I am trying to use qiskit nature in order to calculate the ground state energy of a molecule. My probelm is that when I try to run the simulation an error message comes out:

Traceback (most recent call last):
  Input In [7] in <cell line: 4>
    res = calc.solve(es_problem)
  File /opt/conda/lib/python3.8/site-packages/qiskit_nature/algorithms/ground_state_solvers/ground_state_eigensolver.py:93 in solve
    second_q_ops = problem.second_q_ops()
  File /opt/conda/lib/python3.8/site-packages/qiskit_nature/problems/second_quantization/electronic/electronic_structure_problem.py:94 in second_q_ops
    driver_result = self.driver.run()
  File /opt/conda/lib/python3.8/site-packages/qiskit_nature/drivers/second_quantization/electronic_structure_molecule_driver.py:173 in run
    driver_class = ElectronicStructureDriverType.driver_class_from_type(
  File /opt/conda/lib/python3.8/site-packages/qiskit_nature/drivers/second_quantization/electronic_structure_molecule_driver.py:84 in driver_class_from_type
  File /opt/conda/lib/python3.8/site-packages/qiskit_nature/drivers/second_quantization/pyscfd/pyscfdriver.py:382 in check_installed
    raise MissingOptionalLibraryError(
MissingOptionalLibraryError: The 'PySCF' library is required to use 'PySCFDriver'. You can install it with 'pip install 'qiskit-nature[pyscf]''.  See https://pyscf.org/install.html.

I have installed PySCF using qiskit-nature[pyscf] and I also followed the instructions on pyscf.org , but the message keeps coming out, even if everything is already installed. Where I am doing the mistake? The code I am trying to run is the tutorial: https://qiskit.org/documentation/nature/tutorials/03_ground_state_solvers.html

  • $\begingroup$ pip show pyscf shows its installed right in that environment you are running the tutorial. I have seen a couple of people say similar when they have been using the IBM Quantum Experience - for them re-installing qiskit-nature fixed things. $\endgroup$
    – Steve Wood
    Jun 17 at 15:13
  • $\begingroup$ I gave this command and this is what comes out: Name: pyscf Version: 2.0.1 Summary: PySCF: Python-based Simulations of Chemistry Framework Home-page: pyscf.org Author: Qiming Sun Author-email: osirpt.sun@gmail.com License: Apache License 2.0 Location: /home/natale/.local/lib/python3.8/site-packages Requires: numpy, scipy, h5py Required-by: ; may the problem be that pyscf is in site-packages and qiskit is looking for it in other directories? $\endgroup$ Jun 18 at 15:17

1 Answer 1


try the following step:

  1. (uninstall both pakage)!pip uninstall qiskit_nature --yes
    !pip uninstall pyscf --yes
  2. (check if uninstalled)!pip show qiskit_nature
    !pip show pyscf
  3. (install both package)!pip install qiskit-nature[pyscf] -U or
    (follow sequence) 1.!pip install qiskit-nature 2.pip install pyscf
  4. do the step 2 again check both is installed
  5. restart kernel, it should work like magic.
  • $\begingroup$ I tried but it says on both runs that requirements are already satisfied, so it skips the upgrading... $\endgroup$ Jun 18 at 15:13
  • $\begingroup$ @NataleMatranga uninstall $\endgroup$
    – poig
    Jun 18 at 20:14
  • $\begingroup$ It still doesn't work, I can't figure out why. I uninstalled and installed again, I tried to do this firstly via pip, then conda. $\endgroup$ Jun 20 at 13:07
  • $\begingroup$ @NataleMatranga I edit my answer, I tried the method on IBM lab, it solved the issue. $\endgroup$
    – poig
    Jun 20 at 16:52
  • $\begingroup$ I accept your answer, but it has not solved the problem... it keeps saying that I must install pyscf, but I checked as you said, they are installed... $\endgroup$ Jun 21 at 15:45

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