[BUG] Incorrect state measurement when GlobalPhase decomposes to nothing

[astralcai]

Expected behavior

A circuit should produce the same result for a state measurement whether it is decomposed.

Actual behavior

@qml.qnode(qml.device("default.qubit"))
def circuit():
    qml.X(0)
    return qml.state()

>>> circuit()
array([0.+0.j, 1.+0.j])

but if we decompose the circuit:

@functools.partial(qml.transforms.decompose, gate_set={"RX"})
@qml.qnode(qml.device("default.qubit"))
def circuit():
    qml.X(0)
    return qml.state()

>>> circuit()
array([6.123234e-17+0.j, 0.000000e+00-1.j])

Additional information

No response

Source code

Tracebacks

System information

Name: PennyLane
Version: 0.41.0.dev42
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/xxx/Workspace/pennylane
Requires: appdirs, autograd, autoray, cachetools, diastatic-malt, networkx, numpy, packaging, pennylane-lightning, requests, rustworkx, scipy, tomlkit, typing_extensions
Required-by: PennyLane_Lightning

Platform info:           macOS-15.3.2-arm64-arm-64bit
Python version:          3.10.14
Numpy version:           1.26.4
Scipy version:           1.14.1
Installed devices:
- default.clifford (PennyLane-0.41.0.dev42)
- default.gaussian (PennyLane-0.41.0.dev42)
- default.mixed (PennyLane-0.41.0.dev42)
- default.qubit (PennyLane-0.41.0.dev42)
- default.qutrit (PennyLane-0.41.0.dev42)
- default.qutrit.mixed (PennyLane-0.41.0.dev42)
- default.tensor (PennyLane-0.41.0.dev42)
- null.qubit (PennyLane-0.41.0.dev42)
- reference.qubit (PennyLane-0.41.0.dev42)
- lightning.qubit (PennyLane_Lightning-0.40.0)

Existing GitHub issues

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