Expectation value is a real quantity

UCL-CCS · Nov 28, 2023 · f35bac8 · f35bac8
1 parent da42a45
commit f35bac8
Showing 1 changed file with 2 additions and 2 deletions.
diff --git a/symmer/operators/base.py b/symmer/operators/base.py
@@ -830,7 +830,7 @@ def expval(self, psi: "QuantumState") -> complex:
             complex: The expectation value.
         """
         if self.n_terms > psi.n_terms:
-            return psi.dagger * self * psi
+            return (psi.dagger * self * psi).real
         else:
             if self.n_terms > 1:
                 @process.parallelize
@@ -841,7 +841,7 @@ def f(P, psi):
             else:
                 expvals = np.array(single_term_expval(self, psi))
 
-            return np.sum(expvals * self.coeff_vec)
+            return np.sum(expvals * self.coeff_vec).real
 
     def __mul__(self, 
             mul_obj: Union["PauliwordOp", "QuantumState", complex],