SelectHubbard refactor (#1732)

Use subroutines for `SelectHubbard`. 

- Wrap complex metaprogramming in bespoke hubbard bloqs for
documentability, serializability.
- move towards support for symbolic decomposition: the select circuit
now theoretically could be constructed with symbolic n. There are some
complications when using the cirq-style decomposition though.
- unit test the phasing subroutine using the new phased-classical
simulation tools.

I created a new bloq notebook for select and its subroutines. And I put
the existing hubbard model page under "chemistry" where it belongs.

Author: mpharrigan

dev_tools/qualtran_dev_tools/notebook_specs.py

@@ -368,6 +368,24 @@
         ],
         directory=f'{SOURCE_DIR}/bloqs/chemistry/trotter/hubbard',
     ),
+    NotebookSpecV2(
+        title='Qubitized Hubbard',
+        module=qualtran.bloqs.chemistry.hubbard_model.qubitization,
+        path_stem='hubbard_model',
+        bloq_specs=[
+            qualtran.bloqs.chemistry.hubbard_model.qubitization.select_hubbard._SELECT_HUBBARD_DOC,
+            qualtran.bloqs.chemistry.hubbard_model.qubitization.prepare_hubbard._PREPARE_HUBBARD,
+        ],
+    ),
+    NotebookSpecV2(
+        title='Qubitized Hubbard Select',
+        module=qualtran.bloqs.chemistry.hubbard_model.qubitization.select_hubbard,
+        bloq_specs=[
+            qualtran.bloqs.chemistry.hubbard_model.qubitization.select_hubbard._SELECT_HUBBARD_DOC,
+            qualtran.bloqs.chemistry.hubbard_model.qubitization.select_hubbard._HUBBARD_MAJORANNA_OPERATOR_DOC,
+            qualtran.bloqs.chemistry.hubbard_model.qubitization.select_hubbard._HUBBARD_SPIN_UP_Z_DOC,
+        ],
+    ),
     NotebookSpecV2(
         title='Givens Rotations',
         module=qualtran.bloqs.chemistry.quad_fermion.givens_bloq,
@@ -930,15 +948,6 @@
             qualtran.bloqs.state_preparation.prepare_uniform_superposition._PREP_UNIFORM_DOC
         ],
     ),
-    NotebookSpecV2(
-        title='Qubitized Hubbard Model',
-        module=qualtran.bloqs.chemistry.hubbard_model.qubitization,
-        path_stem='hubbard_model',
-        bloq_specs=[
-            qualtran.bloqs.chemistry.hubbard_model.qubitization.select_hubbard._SELECT_HUBBARD,
-            qualtran.bloqs.chemistry.hubbard_model.qubitization.prepare_hubbard._PREPARE_HUBBARD,
-        ],
-    ),
     NotebookSpecV2(
         title='Apply to Lth Target',
         module=qualtran.bloqs.multiplexers.apply_gate_to_lth_target,

docs/bloqs/index.rst

@@ -63,6 +63,8 @@ Bloqs Library
     chemistry/trotter/trotterized_unitary.ipynb
     chemistry/trotter/ising/ising.ipynb
     chemistry/trotter/hubbard/hubbard.ipynb
+    chemistry/hubbard_model/qubitization/hubbard_model.ipynb
+    chemistry/hubbard_model/qubitization/select_hubbard.ipynb
     chemistry/quad_fermion/givens_bloq.ipynb
 
 .. toctree::
@@ -178,7 +180,6 @@ Bloqs Library
     :caption: Other:
 
     state_preparation/prepare_uniform_superposition.ipynb
-    chemistry/hubbard_model/qubitization/hubbard_model.ipynb
     multiplexers/apply_gate_to_lth_target.ipynb
     multiplexers/apply_lth_bloq.ipynb
     data_loading/qrom.ipynb

qualtran/_infra/composite_bloq.py

@@ -1367,7 +1367,7 @@ def free(self, soq: Soquet, dirty: bool = False) -> None:
 
         self.add(Free(dtype=qdtype, dirty=dirty), reg=soq)
 
-    def split(self, soq: Soquet) -> NDArray[Soquet]:  # type: ignore[type-var]
+    def split(self, soq: SoquetInT) -> NDArray[Soquet]:  # type: ignore[type-var]
         """Add a Split bloq to split up a register."""
         from qualtran.bloqs.bookkeeping import Split
 

qualtran/bloqs/chemistry/hubbard_model/qubitization/__init__.py

@@ -50,5 +50,5 @@
  - $p>q$, YZY term.
 """
 from .prepare_hubbard import PrepareHubbard
-from .select_hubbard import SelectHubbard
+from .select_hubbard import HubbardMajorannaOperator, HubbardSpinUpZ, SelectHubbard
 from .walk_operator import get_walk_operator_for_hubbard_model

qualtran/bloqs/chemistry/hubbard_model/qubitization/hubbard_model.ipynb

@@ -7,7 +7,7 @@
     "cq.autogen": "title_cell"
    },
    "source": [
-    "# Qubitized Hubbard Model\n",
+    "# Qubitized Hubbard\n",
     "\n",
     "Simulating the Hubbard model Hamiltonian using qubitization.\n",
     "\n",
@@ -83,6 +83,8 @@
     "If neither $U$ nor $V$ is set we apply the kinetic terms of the Hamiltonian:\n",
     "\n",
     "$$\n",
+    "\\def\\Zvec{\\overrightarrow{Z}}\n",
+    "\\def\\hop#1{#1_{p,\\sigma} \\Zvec #1_{q,\\sigma}}\n",
     "-\\hop{X} \\quad p < q \\\\\n",
     "-\\hop{Y} \\quad p > q\n",
     "$$\n",