update df trotter tutorial

qiskit-community · Nov 6, 2023 · 7d1c82c · 7d1c82c
1 parent 21d010f
commit 7d1c82c
Showing 1 changed file with 36 additions and 17 deletions.
diff --git a/docs/tutorials/03-double-factorized.ipynb b/docs/tutorials/03-double-factorized.ipynb
@@ -35,7 +35,7 @@
     "\n",
     "where $n_{\\sigma, i} = a^\\dagger_{\\sigma, i} a_{\\sigma, i}$ is the occupation number operator and $\\mathbf{J}_{ij}$ is a real symmetric matrix.\n",
     "\n",
-    "In the cell below, we construct the Hamiltonian for a hydrogen molecule at a stretched bond length and then get the double-factorized representation of the Hamiltonian."
+    "In the cell below, we construct the Hamiltonian for an ethene molecule at a stretched bond length and then get the double-factorized representation of the Hamiltonian."
    ]
   },
   {
@@ -47,14 +47,34 @@
     "import pyscf\n",
     "import ffsim\n",
     "\n",
-    "# Build an H2 molecule\n",
+    "# Build a stretched ethene molecule\n",
+    "bond_distance = 2.678\n",
+    "a = 0.5 * bond_distance\n",
+    "b = a + 0.5626\n",
+    "c = 0.9289\n",
     "mol = pyscf.gto.Mole()\n",
-    "mol.build(atom=[[\"H\", (0, 0, 0)], [\"H\", (0, 0, 1.8)]], basis=\"sto-6g\", symmetry=\"d2h\")\n",
+    "mol.build(\n",
+    "    atom=[\n",
+    "        [\"C\", (0, 0, a)],\n",
+    "        [\"C\", (0, 0, -a)],\n",
+    "        [\"H\", (0, c, b)],\n",
+    "        [\"H\", (0, -c, b)],\n",
+    "        [\"H\", (0, c, -b)],\n",
+    "        [\"H\", (0, -c, -b)],\n",
+    "    ],\n",
+    "    basis=\"sto-6g\",\n",
+    "    symmetry=\"d2h\",\n",
+    ")\n",
     "hartree_fock = pyscf.scf.RHF(mol)\n",
     "hartree_fock.kernel()\n",
     "\n",
+    "# Define active space\n",
+    "active_space = range(mol.nelectron // 2 - 2, mol.nelectron // 2 + 2)\n",
+    "\n",
     "# Get molecular data and molecular Hamiltonian (one- and two-body tensors)\n",
-    "mol_data = ffsim.MolecularData.from_hartree_fock(hartree_fock)\n",
+    "mol_data = ffsim.MolecularData.from_hartree_fock(\n",
+    "    hartree_fock, active_space=active_space\n",
+    ")\n",
     "norb = mol_data.norb\n",
     "nelec = mol_data.nelec\n",
     "mol_hamiltonian = mol_data.hamiltonian\n",
@@ -69,7 +89,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "Here, `mol_hamiltonian` is an instance of `MolecularHamiltonian`, a dataclass that stores the one- and two-body tensors, and `df_hamiltonian` is an instance of `DoubleFactorizedHamiltonian`, a dataclass that stores the updated one-body-tensor, diagonal Coulomb matrices, and orbital rotations. In the cell below, we print out the tensors describing the original and double-factorized representations."
+    "Here, `mol_hamiltonian` is an instance of `MolecularHamiltonian`, a dataclass that stores the one- and two-body tensors, and `df_hamiltonian` is an instance of `DoubleFactorizedHamiltonian`, a dataclass that stores the updated one-body-tensor, diagonal Coulomb matrices, and orbital rotations. In the cell below, we print out the shapes of the tensors describing the original and double-factorized representations."
    ]
   },
   {
@@ -78,26 +98,25 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "# Print some information\n",
     "print(\"Original representation\")\n",
     "print(\"-----------------------\")\n",
-    "print(\"One-body tensor:\")\n",
-    "print(mol_hamiltonian.one_body_tensor)\n",
+    "print(\"One-body tensor shape:\")\n",
+    "print(mol_hamiltonian.one_body_tensor.shape)\n",
     "print()\n",
-    "print(\"Two-body tensor:\")\n",
-    "print(mol_hamiltonian.two_body_tensor)\n",
+    "print(\"Two-body tensor shape:\")\n",
+    "print(mol_hamiltonian.two_body_tensor.shape)\n",
     "print()\n",
     "\n",
     "print(\"Double-factorized representation\")\n",
     "print(\"--------------------------------\")\n",
-    "print(\"One-body tensor:\")\n",
-    "print(df_hamiltonian.one_body_tensor)\n",
+    "print(\"One-body tensor shape:\")\n",
+    "print(df_hamiltonian.one_body_tensor.shape)\n",
     "print()\n",
-    "print(\"Diagonal Coulomb matrices:\")\n",
-    "print(df_hamiltonian.diag_coulomb_mats)\n",
+    "print(\"Diagonal Coulomb matrices shape:\")\n",
+    "print(df_hamiltonian.diag_coulomb_mats.shape)\n",
     "print()\n",
-    "print(\"Orbital rotations:\")\n",
-    "print(df_hamiltonian.orbital_rotations)"
+    "print(\"Orbital rotations shape:\")\n",
+    "print(df_hamiltonian.orbital_rotations.shape)"
    ]
   },
   {
@@ -263,7 +282,7 @@
    "source": [
     "import scipy.sparse.linalg\n",
     "\n",
-    "time = 1.0\n",
+    "time = 5.0\n",
     "\n",
     "exact_state = scipy.sparse.linalg.expm_multiply(\n",
     "    -1j * time * hamiltonian,\n",