[QECGatesCost] Adjustments part 3 (#1333)

* [QECGatesCost] Adjustments part 3

* lint

* restrict num controls

Author: mpharrigan

qualtran/resource_counting/_qubit_counts.py

@@ -110,6 +110,10 @@ def compute(
             return _cbloq_max_width(cbloq._binst_graph, get_callee_cost)
         except (DecomposeNotImplementedError, DecomposeTypeError):
             pass
+        except Exception as e:
+            raise RuntimeError(
+                f"An unexpected error occurred when trying to compute {self} for {bloq}: {e}"
+            ) from e
 
         # Fallback:
         # Use the simple maximum of callees and of this bloq's signature. If there

qualtran/resource_counting/classify_bloqs.py

@@ -230,7 +230,7 @@ def bloq_is_rotation(b: Bloq) -> bool:
     This function has a shim for counting Controlled[Rotation] gates as a rotation, which
     will be remediated when the Qualtran standard library gains a bespoke bloq for each CRot.
     """
-    from qualtran.bloqs.basic_gates import GlobalPhase, SGate, TGate
+    from qualtran.bloqs.basic_gates import SGate, TGate
     from qualtran.bloqs.basic_gates.rotation import (
         CZPowGate,
         Rx,
@@ -242,12 +242,17 @@ def bloq_is_rotation(b: Bloq) -> bool:
     )
 
     if isinstance(b, Controlled):
+        if b.ctrl_spec.num_qubits > 1:
+            return False
+
         # TODO https://github.com/quantumlib/Qualtran/issues/878
         #      explicit representation of all two-qubit rotations.
-        if isinstance(b.subbloq, (SGate, TGate, GlobalPhase)):
+        if isinstance(b.subbloq, (SGate, TGate)):
             return True
 
-        return bloq_is_rotation(b.subbloq)
+        # For historical reasons, this hacky solution for controlled rotations does *not*
+        # do clifford, T angle simplification.
+        return isinstance(b.subbloq, (Rx, Ry, Rz, XPowGate, YPowGate, ZPowGate))
 
     if isinstance(b, CZPowGate):
         return True

qualtran/resource_counting/classify_bloqs_test.py

@@ -18,7 +18,7 @@
 import numpy as np
 import pytest
 
-from qualtran import Bloq, QInt, Signature
+from qualtran import Bloq, CtrlSpec, QInt, Signature
 from qualtran.bloqs.arithmetic import Add
 from qualtran.bloqs.arithmetic.comparison import LessThanConstant
 from qualtran.bloqs.basic_gates import CSwap, Rx, Rz, TGate, YPowGate
@@ -33,6 +33,7 @@
 from qualtran.resource_counting import BloqCountT
 from qualtran.resource_counting.classify_bloqs import (
     _get_basic_bloq_classification,
+    bloq_is_rotation,
     bloq_is_t_like,
     classify_bloq,
     classify_t_count_by_bloq_type,
@@ -112,6 +113,14 @@ def test_classify_bloq_counts_with_custom_bloq_classification():
     assert test_bloq.call_graph()[1].get(TGate()) == sum(classified_bloqs.values())
 
 
+def test_bloq_is_rotation():
+    assert bloq_is_rotation(Rx(np.pi * 0.123))
+    assert not bloq_is_rotation(Rx(np.pi / 2))
+    assert bloq_is_rotation(Rx(np.pi * 0.123).controlled())
+    assert bloq_is_rotation(Rx(np.pi / 2).controlled())
+    assert not bloq_is_rotation(Rx(np.pi).controlled(ctrl_spec=CtrlSpec(cvs=(1, 1))))
+
+
 def test_bloq_is_t_like():
     assert bloq_is_t_like(TGate())
     assert bloq_is_t_like(TGate().adjoint())