bug fix

doc/releases/changelog-dev.md

@@ -126,6 +126,8 @@
 
 <h3>Bug fixes 🐛</h3>
 
+* Fixed a bug in `qml.SPSAOptimizer` that ignored keyword arguments in the objective function.
+
 * `CircuitGraph` can now handle circuits with the same operation instance occuring multiple times.
  [(#5907)](https://github.com/PennyLaneAI/pennylane/pull/5907)
 

pennylane/optimize/spsa.py

@@ -194,6 +194,7 @@ def step_and_cost(self, objective_fn, *args, **kwargs):
  objective function output prior to the step.
  """
  g = self.compute_grad(objective_fn, args, kwargs)
+
  new_args = self.apply_grad(g, args)
 
  self.k += 1
@@ -270,7 +271,8 @@ def compute_grad(self, objective_fn, args, kwargs):
  shots = Shots(objective_fn.device._raw_shot_sequence) # pragma: no cover
  else:
  shots = Shots(None)
- if np.prod(objective_fn.func(*args).shape(objective_fn.device, shots)) > 1:
+
+ if np.prod(objective_fn.func(*args, **kwargs).shape(objective_fn.device, shots)) > 1:
  raise ValueError(
  "The objective function must be a scalar function for the gradient "
  "to be computed."

tests/optimize/test_spsa.py

@@ -443,7 +443,7 @@ def cost(params):
 
  @pytest.mark.usefixtures("use_legacy_opmath")
  @pytest.mark.slow
- def test_lighting_device_legacy_opmath(self):
+ def test_lightning_device_legacy_opmath(self):
  """Test SPSAOptimizer implementation with lightning.qubit device."""
  coeffs = [0.2, -0.543, 0.4514]
  obs = [
@@ -479,7 +479,7 @@ def cost_fun(params, num_qubits=1):
  assert energy < init_energy
 
  @pytest.mark.slow
- def test_lighting_device(self):
+ def test_lightning_device(self):
  """Test SPSAOptimizer implementation with lightning.qubit device."""
  coeffs = [0.2, -0.543, 0.4514]
  obs = [