Minor program capture fixes (#5889)

**Context:**

Catalyst PR #837 (PennyLaneAI/catalyst#837)
needs a couple minor updates to the capture module.

**Description of the Change:**

1) makes it possible to do `from pennylane.capture import
AbstractOperator, AbstractMeasurement, qnode_prim` so we don't have to
touch private functions

2) Adds `qnode` as a keyword argument that gets bound to the qnode
primitive

3) Makes it so we can capture a sample measurement specified like
`qml.sample(wires=1)`

**Benefits:**

**Possible Drawbacks:**

**Related GitHub Issues:**
[sc-66703]

---------

Co-authored-by: David Wierichs <david.wierichs@xanadu.ai>

doc/releases/changelog-dev.md

@@ -282,6 +282,7 @@
  [(#5708)](https://github.com/PennyLaneAI/pennylane/pull/5708)
  [(#5523)](https://github.com/PennyLaneAI/pennylane/pull/5523)
  [(#5686)](https://github.com/PennyLaneAI/pennylane/pull/5686)
+ [(#5889)](https://github.com/PennyLaneAI/pennylane/pull/5889)
 
 * The `decompose` transform has an `error` kwarg to specify the type of error that should be raised,
  allowing error types to be more consistent with the context the `decompose` function is used in.

pennylane/capture/__init__.py

@@ -135,10 +135,45 @@ def _(*args, **kwargs):
 )
 from .capture_qnode import qnode_call
 
+# by defining this here, we avoid
+# E0611: No name 'AbstractOperator' in module 'pennylane.capture' (no-name-in-module)
+# on use of from capture import AbstractOperator
+AbstractOperator: type
+AbstractMeasurement: type
+qnode_prim: "jax.core.Primitive"
+
 
 def __getattr__(key):
  if key == "AbstractOperator":
  from .primitives import _get_abstract_operator # pylint: disable=import-outside-toplevel
 
  return _get_abstract_operator()
+
+ if key == "AbstractMeasurement":
+ from .primitives import _get_abstract_measurement # pylint: disable=import-outside-toplevel
+
+ return _get_abstract_measurement()
+
+ if key == "qnode_prim":
+ from .capture_qnode import _get_qnode_prim # pylint: disable=import-outside-toplevel
+
+ return _get_qnode_prim()
+
  raise AttributeError(f"module 'pennylane.capture' has no attribute '{key}'")
+
+
+__all__ = (
+ "disable",
+ "enable",
+ "enabled",
+ "CaptureMeta",
+ "ABCCaptureMeta",
+ "create_operator_primitive",
+ "create_measurement_obs_primitive",
+ "create_measurement_wires_primitive",
+ "create_measurement_mcm_primitive",
+ "qnode_call",
+ "AbstractOperator",
+ "AbstractMeasurement",
+ "qnode_prim",
+)

pennylane/capture/capture_qnode.py

@@ -61,7 +61,7 @@ def _get_qnode_prim():
  qnode_prim.multiple_results = True
 
  @qnode_prim.def_impl
- def _(*args, shots, device, qnode_kwargs, qfunc_jaxpr):
+ def _(*args, qnode, shots, device, qnode_kwargs, qfunc_jaxpr):
  def qfunc(*inner_args):
  return jax.core.eval_jaxpr(qfunc_jaxpr.jaxpr, qfunc_jaxpr.consts, *inner_args)
 
@@ -70,7 +70,7 @@ def qfunc(*inner_args):
 
  # pylint: disable=unused-argument
  @qnode_prim.def_abstract_eval
- def _(*args, shots, device, qnode_kwargs, qfunc_jaxpr):
+ def _(*args, qnode, shots, device, qnode_kwargs, qfunc_jaxpr):
  mps = qfunc_jaxpr.out_avals
  return _get_shapes_for(*mps, shots=shots, num_device_wires=len(device.wires))
 
@@ -166,6 +166,12 @@ def f(x):
  qnode_kwargs = {"diff_method": qnode.diff_method, **execute_kwargs, **mcm_config}
  qnode_prim = _get_qnode_prim()
 
- return qnode_prim.bind(
- *args, shots=shots, device=qnode.device, qnode_kwargs=qnode_kwargs, qfunc_jaxpr=qfunc_jaxpr
+ res = qnode_prim.bind(
+ *args,
+ shots=shots,
+ qnode=qnode,
+ device=qnode.device,
+ qnode_kwargs=qnode_kwargs,
+ qfunc_jaxpr=qfunc_jaxpr,
  )
+ return res[0] if len(res) == 1 else res

pennylane/measurements/sample.py

@@ -134,7 +134,7 @@ def circuit(x):
  [0, 0]])
 
  """
- return SampleMP(obs=op, wires=wires)
+ return SampleMP(obs=op, wires=None if wires is None else qml.wires.Wires(wires))
 
 
 class SampleMP(SampleMeasurement):

tests/capture/test_capture_qnode.py

@@ -21,9 +21,7 @@
 import pytest
 
 import pennylane as qml
-from pennylane.capture.capture_qnode import _get_qnode_prim
-
-qnode_prim = _get_qnode_prim()
+from pennylane.capture import qnode_prim
 
 pytestmark = pytest.mark.jax
 
@@ -119,6 +117,7 @@ def circuit(x):
  assert jaxpr.out_avals[0] == jax.core.ShapedArray((), fdtype)
 
  assert eqn0.params["device"] == dev
+ assert eqn0.params["qnode"] == circuit
  assert eqn0.params["shots"] == qml.measurements.Shots(None)
  expected_kwargs = {"diff_method": "best"}
  expected_kwargs.update(circuit.execute_kwargs)

tests/capture/test_measurements_capture.py

@@ -20,7 +20,6 @@
 import pytest
 
 import pennylane as qml
-from pennylane.capture.primitives import _get_abstract_measurement
 from pennylane.measurements import (
  ClassicalShadowMP,
  DensityMatrixMP,
@@ -38,9 +37,9 @@
 
 jax = pytest.importorskip("jax")
 
-pytestmark = pytest.mark.jax
+from pennylane.capture import AbstractMeasurement # pylint: disable=wrong-import-position
 
-AbstractMeasurement = _get_abstract_measurement()
+pytestmark = pytest.mark.jax
 
 
 @pytest.fixture(autouse=True)
@@ -453,32 +452,42 @@ def f(c1, c2):
 @pytest.mark.parametrize("x64_mode", (True, False))
 class TestSample:
 
- @pytest.mark.parametrize("wires, dim1_len", [([0, 1, 2], 3), ([], 4)])
+ @pytest.mark.parametrize("wires, dim1_len", [([0, 1, 2], 3), ([], 4), (1, 1)])
  def test_wires(self, wires, dim1_len, x64_mode):
  """Tests capturing samples on wires."""
 
  initial_mode = jax.config.jax_enable_x64
  jax.config.update("jax_enable_x64", x64_mode)
 
- def f(*inner_wires):
- return qml.sample(wires=inner_wires)
+ if isinstance(wires, list):
+
+ def f(*inner_wires):
+ return qml.sample(wires=inner_wires)
 
- jaxpr = jax.make_jaxpr(f)(*wires)
+ jaxpr = jax.make_jaxpr(f)(*wires)
+ else:
+
+ def f(inner_wire):
+ return qml.sample(wires=inner_wire)
+
+ jaxpr = jax.make_jaxpr(f)(wires)
 
  assert len(jaxpr.eqns) == 1
 
  assert jaxpr.eqns[0].primitive == SampleMP._wires_primitive
  assert [x.aval for x in jaxpr.eqns[0].invars] == jaxpr.in_avals
  mp = jaxpr.eqns[0].outvars[0].aval
  assert isinstance(mp, AbstractMeasurement)
- assert mp.n_wires == len(wires)
+ assert mp.n_wires == len(wires) if isinstance(wires, list) else 1
  assert mp._abstract_eval == SampleMP._abstract_eval
 
  shapes = _get_shapes_for(
  *jaxpr.out_avals, shots=qml.measurements.Shots(50), num_device_wires=4
  )
+ assert len(shapes) == 1
+ shape = (50, dim1_len) if isinstance(wires, list) else (50,)
  assert shapes[0] == jax.core.ShapedArray(
- (50, dim1_len), jax.numpy.int64 if x64_mode else jax.numpy.int32
+ shape, jax.numpy.int64 if x64_mode else jax.numpy.int32
  )
 
  with pytest.raises(ValueError, match="finite shots are required"):

tests/capture/test_operators.py

@@ -18,13 +18,12 @@
 import pytest
 
 import pennylane as qml
-from pennylane.capture.primitives import _get_abstract_operator
 
 jax = pytest.importorskip("jax")
 
-pytestmark = pytest.mark.jax
+from pennylane.capture import AbstractOperator # pylint: disable=wrong-import-position
 
-AbstractOperator = _get_abstract_operator()
+pytestmark = pytest.mark.jax
 
 
 @pytest.fixture(autouse=True)

tests/capture/test_templates.py

@@ -23,14 +23,12 @@
 import pytest
 
 import pennylane as qml
-from pennylane.capture.primitives import _get_abstract_operator
 
 jax = pytest.importorskip("jax")
 jnp = jax.numpy
 
 pytestmark = pytest.mark.jax
 
-AbstractOperator = _get_abstract_operator()
 original_op_bind_code = qml.operation.Operator._primitive_bind_call.__code__