Created generalized evolution operator for uccsd (#68)

* Adds generalized UCCSD evolution operator and abstracts singlet case to a special instance of this operator.

Author: hsim13372

src/fermilib/utils/_unitary_cc.py

@@ -209,6 +209,34 @@ def t2_ind(i, j, k, l):
     return uccsd_generator
 
 
+def uccsd_evolution(fermion_generator, fermion_transform=jordan_wigner):
+    """Create a ProjectQ evolution operator for a UCCSD circuit
+
+    Args:
+        fermion_generator(FermionOperator): UCCSD generator to evolve.
+        fermion_transform(fermilib.transform): The transformation that
+            defines the mapping from Fermions to QubitOperator.
+
+    Returns:
+        evoution_operator(projectq.ops.TimeEvolution): The unitary operator
+            that constructs the UCCSD state.
+    """
+
+    # Transform generator to qubits
+    qubit_generator = fermion_transform(fermion_generator)
+
+    # Cast to real part only for compatibility with current ProjectQ routine
+    for key in qubit_generator.terms:
+        qubit_generator.terms[key] = float(qubit_generator.terms[key].imag)
+    qubit_generator.compress()
+
+    # Allocate wavefunction and act evolution on gate according to compilation
+    evolution_operator = (
+        projectq.ops.TimeEvolution(time=1., hamiltonian=qubit_generator))
+
+    return evolution_operator
+
+
 def uccsd_singlet_evolution(packed_amplitudes, n_qubits, n_electrons,
                             fermion_transform=jordan_wigner):
     """Create a ProjectQ evolution operator for a UCCSD singlet circuit
@@ -232,17 +260,9 @@ def uccsd_singlet_evolution(packed_amplitudes, n_qubits, n_electrons,
     fermion_generator = uccsd_singlet_operator(packed_amplitudes,
                                                n_qubits,
                                                n_electrons)
-    # Transform generator to qubits
-    qubit_generator = fermion_transform(fermion_generator)
 
-    # Cast to real part only for compatibility with current ProjectQ routine
-    for key in qubit_generator.terms:
-        qubit_generator.terms[key] = float(qubit_generator.terms[key].imag)
-    qubit_generator.compress()
-
-    # Allocate wavefunction and act evolution on gate according to compilation
-    evolution_operator = (
-        projectq.ops.TimeEvolution(time=1., hamiltonian=qubit_generator))
+    evolution_operator = uccsd_evolution(fermion_generator,
+                                         fermion_transform)
 
     return evolution_operator
 

src/fermilib/utils/_unitary_cc_test.py

@@ -16,6 +16,7 @@
 
 import unittest
 from numpy.random import randn
+import itertools
 
 import fermilib
 import fermilib.ops