Merge pull request #11 from Schoyen/two-body-exp-val

Add options for two-body operator when computing expectation values

.travis.yml

@@ -1,7 +1,6 @@
 language: python
 python:
-- '3.6'
-- '3.7'
+- '3.8'
 install:
 - pip install pipenv
 - pipenv install --skip-lock

Pipfile

@@ -7,7 +7,6 @@ verify_ssl = true
 
 [packages]
 pytest = "*"
-tdhf = {editable = true,git = "ssh://[email protected]/haakoek/tdhf.git"}
 black = "*"
 matplotlib = "*"
 tqdm = "*"

configuration_interaction/ci.py

@@ -284,7 +284,7 @@ def compute_one_body_density_matrix(self, K=0):
 
         return rho_qp
 
-    def compute_two_body_expectation_value(self, op, K=0):
+    def compute_two_body_expectation_value(self, op, K=0, asym=True):
         r"""Function computing the expectation value of a two-body operator.
         For a given two-body operator :math:`\hat{A}`, we compute the
         expectation value by
@@ -301,6 +301,10 @@ def compute_two_body_expectation_value(self, op, K=0):
             density matrix, i.e., the number of basis functions ``l``.
         K : int
             The eigenstate to use for the two-body density matrix.
+        asym: bool
+            Toggle whether or not ``op`` is anti-symmetrized or not. This
+            determines the prefactor when tracing the two-body density matrix
+            with the two-body operator. Default is ``True``.
 
         Returns
         -------
@@ -314,7 +318,7 @@ def compute_two_body_expectation_value(self, op, K=0):
         """
         rho_rspq = self.compute_two_body_density_matrix(K=K)
 
-        return 0.25 * self.np.tensordot(
+        return (0.25 if asym else 0.5) * self.np.tensordot(
             op, rho_rspq, axes=((0, 1, 2, 3), (2, 3, 0, 1))
         )