qc2 workflow

Code workflow diagram

qc2 is designed around the qc2Data. This class connects with traditional quantum chemistry codes via custom qc2-ASE calculators and the formatted QCSchema or FCIdump [KH89] data files generated from them. qc2Data is then able to read these files and create instances of FCIdump and QCSchema dataclasses; see Qiskit Nature documentation.

Note

Since qc2 primarily operates with data files, you could, in principle, use any traditional quantum chemistry backend other than ASE to generate qchem data. This is possible as long as your backend dumps the necessary data in accordance with the above-mentioned schema.

With the FCIdump and QCSchema dataclasses at hand, qc2Data can seamlessly integrate with Qiskit Nature and build up the active-space molecular Hamiltonian in qubit representation via get_qubit_hamiltonian(). This function uses Qiskit Nature routines and returns the Hamiltonian in Qiskit format.

Warning

By being naturally compatible with Qiskit Nature, qc2Data does not yet directly communicate with PennyLane, a feature that will be available in the near future.

However, If you want to use PennyLane, get_qubit_hamiltonian() can internally convert the Qiskit Hamiltonian into Pennylane format by resorting to _qiskit_nature_to_pennylane().

Once an appropriate form of the qubit Hamiltonian is obtained, VQE calculations can be performed using the quantum computing library of choice. Examples on how to perform such calculations will be later given in the Tutorials and can also be found in the examples directory.