[BUG] Inconsistent behavior between lighning.qubit and default.qubit

[PabloAMC]

Expected behavior

The following code

dev1 = qml.device("lightning.qubit", wires=1)

@qml.qnode(dev1)
def circuit2(phi1, phi2):
    qml.RX(phi1, wires=0)
    qml.RY(phi2, wires=0)
    return qml.expval(qml.PauliZ(0))

phi1 = np.array([0.54])
phi2 = np.array([0.12])
circuit2(phi1, phi2)

should return similar results no matter whether we use lightning.qubit or default.qubit as the device.

Actual behavior

However, if the device is lightning.qubit, the output is Array(0.85154057, dtype=float32, weak_type=True) while if we use default.qubit the result is Array([0.85154057], dtype=float32).

Additional information

No response

Source code

No response

Tracebacks

No response

System information

Name: PennyLane
Version: 0.37.0.dev0
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: https://github.com/PennyLaneAI/pennylane
Author: 
Author-email: 
License: Apache License 2.0
Location: /Users/user/miniforge3/envs/vw/lib/python3.12/site-packages
Editable project location: /Users/pablo.casares/Developer/pennylane
Requires: appdirs, autograd, autoray, cachetools, networkx, numpy, packaging, pennylane-lightning, requests, rustworkx, scipy, semantic-version, toml, typing-extensions
Required-by: PennyLane-qiskit, PennyLane_Lightning

Platform info:           macOS-14.5-arm64-arm-64bit
Python version:          3.12.3
Numpy version:           1.26.4
Scipy version:           1.13.0
Installed devices:
- default.clifford (PennyLane-0.37.0.dev0)
- default.gaussian (PennyLane-0.37.0.dev0)
- default.mixed (PennyLane-0.37.0.dev0)
- default.qubit (PennyLane-0.37.0.dev0)
- default.qubit.autograd (PennyLane-0.37.0.dev0)
- default.qubit.jax (PennyLane-0.37.0.dev0)
- default.qubit.legacy (PennyLane-0.37.0.dev0)
- default.qubit.tf (PennyLane-0.37.0.dev0)
- default.qubit.torch (PennyLane-0.37.0.dev0)
- default.qutrit (PennyLane-0.37.0.dev0)
- default.qutrit.mixed (PennyLane-0.37.0.dev0)
- default.tensor (PennyLane-0.37.0.dev0)
- null.qubit (PennyLane-0.37.0.dev0)
- qiskit.aer (PennyLane-qiskit-0.36.0)
- qiskit.basicaer (PennyLane-qiskit-0.36.0)
- qiskit.basicsim (PennyLane-qiskit-0.36.0)
- qiskit.ibmq (PennyLane-qiskit-0.36.0)
- qiskit.ibmq.circuit_runner (PennyLane-qiskit-0.36.0)
- qiskit.ibmq.sampler (PennyLane-qiskit-0.36.0)
- qiskit.remote (PennyLane-qiskit-0.36.0)
- lightning.qubit (PennyLane_Lightning-0.37.0.dev49)

Existing GitHub issues

• [X] I have searched existing GitHub issues to make sure the issue does not already exist.

[albi3ro]

Might be worth renaming "broadcast_expand squeezes out batch sizes of 1", as that is the root cause of this issue.