Add import_state docs to the website (#4461)

doc/introduction/chemistry.rst

@@ -40,10 +40,7 @@ with an external backend that uses the
 `OpenFermion-PySCF <https://github.com/quantumlib/OpenFermion-PySCF>`_ plugin interfaced with the
 electronic structure package `PySCF <https://github.com/sunqm/pyscf>`_, which requires separate
 installation. This backend is non-differentiable and can be selected by setting
-``method='pyscf'`` in :func:`~.molecular_hamiltonian`. Additionally, if the electronic Hamiltonian
-is built independently using `OpenFermion <https://github.com/quantumlib/OpenFermion>`_ tools, it
-can be readily converted to a PennyLane observable using the
-:func:`~.pennylane.import_operator` function.
+``method='pyscf'`` in :func:`~.molecular_hamiltonian`. 
 
 Furthermore, the net charge,
 the `spin multiplicity <https://en.wikipedia.org/wiki/Multiplicity_(chemistry)>`_, the
@@ -63,6 +60,18 @@ specified for each backend.
         active_orbitals=2
     )
 
+Importing the Hamiltonian and ansatz state
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+If the electronic Hamiltonian is built independently using 
+`OpenFermion <https://github.com/quantumlib/OpenFermion>`_ tools, it can be readily converted 
+to a PennyLane observable using the :func:`~.pennylane.import_operator` function. There is also 
+capability to import wavefunctions (states) that have been pre-computed by traditional quantum chemistry methods
+from `PySCF <https://github.com/sunqm/pyscf>`_, which could be used to for example to provide a better 
+starting point to a quantum algorithm. State import can be accomplished using the :func:`~pennylane.import_state` 
+utility function.
+
+
 Importing molecular structure data
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
@@ -255,6 +264,7 @@ Utility functions
     ~pennylane.qchem.givens_decomposition
     ~pennylane.qchem.hf_state
     ~pennylane.import_operator
+    ~pennylane.import_state
     ~pennylane.qchem.mol_data
     ~pennylane.qchem.read_structure
 

doc/releases/changelog-dev.md

@@ -61,7 +61,7 @@ array([False, False])
   ```
 
   The currently supported objects are RCISD, UCISD, RCCSD, and UCCSD which correspond to 
-  restricted (R) and unrestricted (U) configuration interaction (CI )and coupled cluster (CC) 
+  restricted (R) and unrestricted (U) configuration interaction (CI) and coupled cluster (CC) 
   calculations with single and double (SD) excitations.
 
 <h3>Improvements 🛠</h3>
@@ -287,6 +287,9 @@ array([False, False])
   some aspects of its use.
   [(#4391)](https://github.com/PennyLaneAI/pennylane/pull/4391)
 
+* `qml.import_state` is now accounted for in `doc/introduction/chemistry.rst`, adding the documentation for the function.
+  [(#4461)](https://github.com/PennyLaneAI/pennylane/pull/4461)
+
 <h3>Bug fixes 🐛</h3>
 
 * Allow sparse matrix calculation of `SProd`s containing a `Tensor`. When using

pennylane/__init__.py

@@ -38,7 +38,14 @@
 import pennylane.resource
 import pennylane.qchem
 from pennylane.fermi import FermiC, FermiA, jordan_wigner
-from pennylane.qchem import taper, symmetry_generators, paulix_ops, taper_operation, import_operator
+from pennylane.qchem import (
+    taper,
+    symmetry_generators,
+    paulix_ops,
+    taper_operation,
+    import_operator,
+    import_state,
+)
 from pennylane._device import Device, DeviceError
 from pennylane._grad import grad, jacobian
 from pennylane._qubit_device import QubitDevice