Closes 151

src/qforte/abc/algorithm.py

@@ -75,10 +75,6 @@ def __init__(self,
                  print_summary_file=False,
                  **kwargs):
 
-        if isinstance(self, qf.QPE) and hasattr(system, 'frozen_core'):
-            if system.frozen_core + system.frozen_virtual > 0:
-                raise ValueError("QPE with frozen orbitals is not currently supported.")
-
         self._sys = system
         self._state_prep_type = state_prep_type
 

src/qforte/qpea/qpe.py

@@ -24,7 +24,9 @@ def run(self,
         guess_energy : A guess for the eigenvalue of the eigenspace with which |0>^(n)
             has greatest overlap. You should be confident the ground state is within
         t : A scaling parameter that controls the precision of the computation. You should
-            confident that the eigenvalue of interest is within +/- t of the guess energy.
+            confident that the eigenvalue of interest is within +/- 2pi/t of the guess energy.
+            Larger t's lead to fewer resources for the same amount of precision, but require
+            more confidence in the guess energy.
         """
 
         # float: evolution times

tests/test_freeze_orb.py

@@ -1,6 +1,6 @@
 import pytest
 from pytest import approx
-from qforte import system_factory, UCCNVQE, ADAPTVQE, UCCNPQE, SPQE
+from qforte import system_factory, UCCNVQE, ADAPTVQE, UCCNPQE, SPQE, QPE
 
 class TestFreezingOrbitals():
 
@@ -31,3 +31,26 @@ def test_freeze_orb_ucc(self, method, options):
         Efci = -28.747184707540754
 
         assert Egs == approx(Efci, abs=1.0e-10)
+
+    def test_freeze_orb_qkd(self):
+
+        mol = system_factory(system_type = 'molecule',
+                                     build_type = 'psi4',
+                                     basis = 'sto-3g',
+                                     mol_geometry = [('Be', (0, 0, -1.2)),
+                                                     ('Be', (0, 0,  1.2))],
+                                     symmetry = 'd2h',
+                                     num_frozen_docc = 2,
+                                     num_frozen_uocc = 3)
+
+        alg = QPE(mol)
+
+        alg.run(-28.75, nruns=100, num_precise_bits=5, t=100)
+
+        Egs = alg.get_gs_energy()
+        # WARNING: Due to a bug in Psi4, the energies stored in the fci_energy attrbitute of the Molecule class are not
+        #          correct when the number of frozen virtual orbitals is larger than zero.
+        Efci = -28.747184707540754
+
+        assert Egs == approx(Efci, abs=1.1e-3)
+