Hello!

I am currently facing the issue that when I include PhasShift gates in my circuit im my QML project I get a ‘casting imaginary to real’ warning. This warning emerges when calling the step_and_cost method of ADAM.

```
from pennylane import numpy as np
import pennylane as qml
from pennylane.optimize import AdamOptimizer
dev = qml.device("default.qubit")
# create random data with complex amplitudes and binary classification label
X_train = np.random.rand(100, 2) + 1j * np.random.rand(100, 2)
Y_train = np.random.randint(low = 0, high=2, size=(100,1))
# define circuit with phase shift gate
@qml.qnode(dev)
def shift_circuit(state, weight):
qml.QubitStateVector(state, wires=range(1), normalize=True)
qml.PhaseShift(weight[0], 0)
return qml.expval(qml.PauliZ(0))
# cost function with MSE of batch prediction
def cost(weights, X, Y):
predictions = np.array([shift_circuit(x, weights) for x in X])
return np.sum((Y - predictions)**2)
opt = AdamOptimizer()
q_weights = np.ones(1)
# optimisation run with
for it in range(3):
batch_index = np.random.randint(0, len(X_train), (5,))
X_batch = X_train[batch_index]
Y_batch = Y_train[batch_index]
q_weights, loss = opt.step_and_cost(cost, q_weights, X=X_batch, Y=Y_batch)
```

The warning message is the following and I get it for every iteration

```
/opt/miniconda3/lib/python3.12/site-packages/autograd/numpy/numpy_wrapper.py:156: ComplexWarning: Casting complex values to real discards the imaginary part
return A.astype(dtype, order, casting, subok, copy)
```

Here is the qml.about() information:

Name: PennyLane

Version: 0.38.0

Summary: PennyLane is a cross-platform Python library for quantum computing, quantum machine learning, and quantum chemistry. Train a quantum computer the same way as a neural network.

Home-page: GitHub - PennyLaneAI/pennylane: PennyLane is a cross-platform Python library for quantum computing, quantum machine learning, and quantum chemistry. Train a quantum computer the same way as a neural network.

Author:

Author-email:

License: Apache License 2.0

Location: /opt/miniconda3/lib/python3.12/site-packages

Requires: appdirs, autograd, autoray, cachetools, networkx, numpy, packaging, pennylane-lightning, requests, rustworkx, scipy, toml, typing-extensions

Required-by: PennyLane_Lightning

Platform info: macOS-15.0.1-arm64-arm-64bit

Python version: 3.12.1

Numpy version: 1.26.4

Scipy version: 1.14.1

Installed devices:

- lightning.qubit (PennyLane_Lightning-0.38.0)
- default.clifford (PennyLane-0.38.0)
- default.gaussian (PennyLane-0.38.0)
- default.mixed (PennyLane-0.38.0)
- default.qubit (PennyLane-0.38.0)
- default.qubit.autograd (PennyLane-0.38.0)
- default.qubit.jax (PennyLane-0.38.0)
- default.qubit.legacy (PennyLane-0.38.0)
- default.qubit.tf (PennyLane-0.38.0)
- default.qubit.torch (PennyLane-0.38.0)
- default.qutrit (PennyLane-0.38.0)
- default.qutrit.mixed (PennyLane-0.38.0)
- default.tensor (PennyLane-0.38.0)
- null.qubit (PennyLane-0.38.0)

Thanks in advance!