# Qml.device error with qiskit.aer

**URL:** <https://discuss.pennylane.ai/t/qml-device-error-with-qiskit-aer/4556>\
**Category:** PennyLane Qiskit\
**Created:** [May 3, 2024, 4:37am UTC](https://discuss.pennylane.ai/t/qml-device-error-with-qiskit-aer/4556 "2024-05-03T04:37:45Z")\
**Posts on this page:** 18\
**Page:** 1

<div class="post-metadata">

**Author:** ![art](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/art/32/1126_2.png) [@art](https://discuss.pennylane.ai/u/art)\
**Post date:** [May 3, 2024, 4:37am UTC](https://discuss.pennylane.ai/t/qml-device-error-with-qiskit-aer/4556/1 "2024-05-03T04:37:45Z")

</div>

After creating a conda python 3.9 environment and activating it  
I ran the following command:

```auto
pip3 install -r tutorial_requirements.txt

```

from the following page:

> **[GitHub - QuTAM/QuFI: Quantum Fault Injector](https://github.com/QuTAM/QuFI?tab=readme-ov-file)**
>
> Quantum Fault Injector. Contribute to QuTAM/QuFI development by creating an account on GitHub.

The I ran the following code and got the error as shown.

```auto
import pennylane as qml

import qiskit
import pennylane as qml
from pennylane import numpy as np

dev = qml.device('qiskit.aer',wires=2, shots=10)

@qml.qnode(dev)
def circuit(w):
    qml.Hadamard(wires=0)
    qml.RX(w,wires=0)
    return qml.expval(qml.PauliZ(0))

w=np.array(0.1,requires_grad=True)

opt = qml.GradientDescentOptimizer(stepsize=0.1)
w, cost = opt.step_and_cost(circuit, w)
print(cost)

```

Error message:

```auto
Traceback (most recent call last):
  File "/media/xxx/C-UAS-DB1/QuFI/test_aer.py", line 8, in <module>
    dev = qml.device('qiskit.aer',wires=2, shots=10)
  File "/home/xxx/anaconda/envs/qufi2/lib/python3.9/site-packages/pennylane/ __init__.py", line 338, in device
    raise DeviceError("Device does not exist. Make sure the required plugin is installed.")
pennylane._device.DeviceError: Device does not exist. Make sure the required plugin is installed.

```

```auto
>>> qml.about()
Name: PennyLane
Version: 0.30.0
Summary: PennyLane is a Python quantum machine learning library by Xanadu Inc.
Home-page: https://github.com/XanaduAI/pennylane
Author: 
Author-email: 
License: Apache License 2.0
Location: /home/xxx/anaconda/envs/qufi2/lib/python3.9/site-packages
Requires: appdirs, autograd, autoray, cachetools, networkx, numpy, pennylane-lightning, requests, rustworkx, scipy, semantic-version, toml
Required-by: PennyLane-Lightning

Platform info: Linux-5.4.0-150-generic-x86_64-with-glibc2.27
Python version: 3.9.19
Numpy version: 1.23.5
Scipy version: 1.10.1
Installed devices:
- default.gaussian (PennyLane-0.30.0)
- default.mixed (PennyLane-0.30.0)
- default.qubit (PennyLane-0.30.0)
- default.qubit.autograd (PennyLane-0.30.0)
- default.qubit.jax (PennyLane-0.30.0)
- default.qubit.tf (PennyLane-0.30.0)
- default.qubit.torch (PennyLane-0.30.0)
- default.qutrit (PennyLane-0.30.0)
- null.qubit (PennyLane-0.30.0)
- lightning.qubit (PennyLane-Lightning-0.30.0)

```

I also get the same error when I run the run\_circuits.py script from the github page. What could be the issue here?

---

<div class="post-metadata">

**Author:** ![CatalinaAlbornoz](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/catalinaalbornoz/32/1196_2.png) [@CatalinaAlbornoz](https://discuss.pennylane.ai/u/CatalinaAlbornoz)\
**Post date:** [May 3, 2024, 2:58pm UTC](https://discuss.pennylane.ai/t/qml-device-error-with-qiskit-aer/4556/2 "2024-05-03T14:58:17Z")

</div>

Hi @art, it looks like you need to install the PennyLane-Qiskit plugin.

You can run `pip install pennylane-qiskit`. However I’m not sure what version you will need since you’re using an older version of PennyLane and Qiskit.

You can try running `pip install PennyLane-qiskit==0.30.0` and then try setting the version of Qiskit according to the error message that you get.

If you’re interested in running the snippet of code you shared with the latest version of everything then I recommend that you wait until Tuesday when we will have a new PennyLane release. Then you can run `pip install --upgrade pennylane pennylane-qiskit`

If you don’t want to wait then you can install PennyLane and the Qiskit plugin from source with the following code:

```auto
pip install git+https://github.com/PennyLaneAI/pennylane.git#egg=pennylane
pip install git+https://github.com/PennyLaneAI/pennylane-qiskit.git

```

I hope this helps you

---

<div class="post-metadata">

**Author:** ![art](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/art/32/1126_2.png) [@art](https://discuss.pennylane.ai/u/art)\
**Post date:** [May 5, 2024, 2:37am UTC](https://discuss.pennylane.ai/t/qml-device-error-with-qiskit-aer/4556/3 "2024-05-05T02:37:51Z")

</div>

I did the last two pip installs. Now the code snippet runs but  
run\_circuits.py gives the following error:

```auto

Traceback (most recent call last):
  File "/media/xxx/C-UAS-DB1/QuFI/run_circuits.py", line 3, in <module>
    from qiskit.providers.fake_provider import FakeSantiago
ImportError: cannot import name 'FakeSantiago' from 'qiskit.providers.fake_provider' (/home/xxx/anaconda/envs/qufi2/lib/python3.9/site-packages/qiskit/providers/fake_provider/ __init__.py)

```

```auto
>>> qml.about()
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: /home/xxx/anaconda/envs/qufi2/lib/python3.9/site-packages
Requires: appdirs, autograd, autoray, cachetools, networkx, numpy, pennylane-lightning, requests, rustworkx, scipy, semantic-version, toml, typing-extensions
Required-by: PennyLane-qiskit, PennyLane_Lightning

Platform info: Linux-5.4.0-150-generic-x86_64-with-glibc2.27
Python version: 3.9.19
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)
- null.qubit (PennyLane-0.37.0.dev0)
- lightning.qubit (PennyLane-Lightning-0.35.1)
- 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)

```

---

<div class="post-metadata">

**Author:** ![CatalinaAlbornoz](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/catalinaalbornoz/32/1196_2.png) [@CatalinaAlbornoz](https://discuss.pennylane.ai/u/CatalinaAlbornoz)\
**Post date:** [May 8, 2024, 12:52am UTC](https://discuss.pennylane.ai/t/qml-device-error-with-qiskit-aer/4556/4 "2024-05-08T00:52:20Z")

</div>

Hi @art ,

It seems that Qiskit has changed their functionality and removed the old fake backends. Check their first example in their documentation [here](https://docs.quantum.ibm.com/api/qiskit/providers_fake_provider) to learn how to use the new GenericBackend they have.

Since a lot has changed in Qiskit and PennyLane in two years (when the QuFI project was written), it’s possible that you will encounter many other similar errors. If you get more of these errors you should try looking up online to see what the new Qiskit functionality is in those cases.

I hope this helps you!

---

<div class="post-metadata">

**Author:** ![art](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/art/32/1126_2.png) [@art](https://discuss.pennylane.ai/u/art)\
**Post date:** [May 8, 2024, 4:42pm UTC](https://discuss.pennylane.ai/t/qml-device-error-with-qiskit-aer/4556/5 "2024-05-08T16:42:25Z")

</div>

I switched over to the Brisbane backend.  
Now I get a pennylane error from injector.py.  
What happened to the qml.qfunc\_transform decorator?  
There is no pennylane page on that also.

```auto

    from qufi import execute_over_range, BernsteinVazirani, get_qiskit_coupling_map, read_results_directory, generate_all_statistics
  File "/media/xxx/C-UAS-DB1/QuFI/qufi/ __init__.py", line 1, in <module>
    from qufi.injector import *
  File "/media/xxx/C-UAS-DB1/QuFI/qufi/injector.py", line 131, in <module>
    @qml.qfunc_transform
  File "/home/xxx/anaconda/envs/qufi2/lib/python3.9/site-packages/pennylane/ __init__.py", line 164, in __getattr__
    raise AttributeError(f"module 'pennylane' has no attribute '{name}'")
AttributeError: module 'pennylane' has no attribute 'qfunc_transform'

```

---

<div class="post-metadata">

**Author:** ![art](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/art/32/1126_2.png) [@art](https://discuss.pennylane.ai/u/art)\
**Post date:** [May 8, 2024, 5:47pm UTC](https://discuss.pennylane.ai/t/qml-device-error-with-qiskit-aer/4556/6 "2024-05-08T17:47:17Z")

</div>

Replacing @qml.func\_transform by @qml.transform solved the issue.

---

<div class="post-metadata">

**Author:** ![art](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/art/32/1126_2.png) [@art](https://discuss.pennylane.ai/u/art)\
**Post date:** [May 8, 2024, 6:00pm UTC](https://discuss.pennylane.ai/t/qml-device-error-with-qiskit-aer/4556/7 "2024-05-08T18:00:12Z")

</div>

I was able to use the FakeSantiago backend by using the line:  
from qiskit\_ibm\_runtime.fake\_provider import FakeSantiago

Now I am getting a “cannot pickle ‘pennylane\_lightning.lightning\_qubit\_ops.StateVectorC128’ object”  
error issued by deepcopy() in injector.py. Any suggestions?

```auto
--------------------------------------------------------------------------------

Circuit Bernstein-Vazirani_4 start: 2024-05-08 13:50:21.185230
--------------------------------------------------------------------------------
Injecting circuit: Bernstein-Vazirani_4 theta0: 0 phi0: 0
Traceback (most recent call last):
  File "/media/xxx/C-UAS-DB1/QuFI/run_circuits.py", line 24, in <module>
    results_names = execute_over_range(circuits, angles, coupling_map=coupling_map, results_folder="./tmp/")
  File "/media/xxx/C-UAS-DB1/QuFI/qufi/injector.py", line 277, in execute_over_range
    copy_of_circuit = deepcopy(target_circuit) # pickle error here
  File "/home/xxx/anaconda/envs/qufi2/lib/python3.9/copy.py", line 172, in deepcopy
    y = _reconstruct(x, memo, *rv)
  File "/home/xxx/anaconda/envs/qufi2/lib/python3.9/copy.py", line 270, in _reconstruct
    state = deepcopy(state, memo)
  File "/home/xxx/anaconda/envs/qufi2/lib/python3.9/copy.py", line 146, in deepcopy
    y = copier(x, memo)
  File "/home/xxx/anaconda/envs/qufi2/lib/python3.9/copy.py", line 230, in _deepcopy_dict
    y[deepcopy(key, memo)] = deepcopy(value, memo)
  File "/home/xxx/anaconda/envs/qufi2/lib/python3.9/copy.py", line 172, in deepcopy
    y = _reconstruct(x, memo, *rv)
  File "/home/xxx/anaconda/envs/qufi2/lib/python3.9/copy.py", line 270, in _reconstruct
    state = deepcopy(state, memo)
  File "/home/xxx/anaconda/envs/qufi2/lib/python3.9/copy.py", line 146, in deepcopy
    y = copier(x, memo)
  File "/home/xxx/anaconda/envs/qufi2/lib/python3.9/copy.py", line 230, in _deepcopy_dict
    y[deepcopy(key, memo)] = deepcopy(value, memo)
  File "/home/xxx/anaconda/envs/qufi2/lib/python3.9/copy.py", line 161, in deepcopy
    rv = reductor(4)
TypeError: cannot pickle 'pennylane_lightning.lightning_qubit_ops.StateVectorC128' object

```

---

<div class="post-metadata">

**Author:** ![CatalinaAlbornoz](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/catalinaalbornoz/32/1196_2.png) [@CatalinaAlbornoz](https://discuss.pennylane.ai/u/CatalinaAlbornoz)\
**Post date:** [May 10, 2024, 1:16am UTC](https://discuss.pennylane.ai/t/qml-device-error-with-qiskit-aer/4556/8 "2024-05-10T01:16:15Z")

</div>

Hi @art,

Indeed @qml.func\_transform was deprecated and you should now use @qml.transform. You can see more details in the [Deprecations section of the documentation](https://docs.pennylane.ai/en/stable/development/deprecations.html?highlight=qfunc_transform#completed-deprecation-cycles).

Ah it’s interesting to see that Qiskit has moved the fake providers to qiskit\_ibm\_runtime. Good find.

From your last error it seems that the QuFI project is using Python’s deepcopy to do something. this is being called in l[ine 271 of the injector.py](https://github.com/QuTAM/QuFI/blob/689e088e296ccaa67b4b6cf0544ed025ce5336be/qufi/injector.py#L271) file and in other places too. It seems that this operation is incompatible with lightning.qubit. It looks like `lightning.qubit` is being called in QuFI’s circuit\_generator and injector files so I would recommend that you change them to use `default.qubit` instead and test if this resolves the problem.

---

<div class="post-metadata">

**Author:** ![art](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/art/32/1126_2.png) [@art](https://discuss.pennylane.ai/u/art)\
**Post date:** [May 10, 2024, 3:33am UTC](https://discuss.pennylane.ai/t/qml-device-error-with-qiskit-aer/4556/9 "2024-05-10T03:33:56Z")

</div>

@CatalinaAlbornoz earlier I had made the lightning.qubit to default.qubit changes in injector.py but I also needed to make the same changes in circuit\_generator.py. That fixed the deepcopy error.

How would I go about changing qml.qfunc\_transform decorators to qml.transform for the following code (using @partial(…))?

```auto
@qml.qfunc_transform
def pl_insert_gate(tape, index, wire, theta=0, phi=0, lam=0):
    """Decorator qfunc_transform which inserts a single fault gate"""
    i = 0
    for gate in tape.operations + tape.measurements:
        # Ignore barriers and measurement gates
        if i == index:
            # If gate are not using a single qubit, insert one gate after each qubit
            qml.apply(gate)
            qml.U3(theta=theta, phi=phi, delta=lam, wires=wire, id="FAULT")
        else:
            qml.apply(gate)
        i = i + 1

def pl_generate_circuits(base_circuit, name, theta=0, phi=0, lam=0):
    """Generate all possible fault circuits"""
    mycircuits = []
    inj_info = []
    index_info = []
    op_info = []
    # with tape as tape:
    index = 0
    for op in base_circuit.tape.operations:
        for wire in op.wires:
            shots = 1024
            transformed_circuit = pl_insert_gate(index, wire, theta, phi, lam)(base_circuit.func)
            device = qml.device('default.qubit', wires=len(base_circuit.tape.wires), shots=shots)
            transformed_qnode = qml.QNode(transformed_circuit, device)
            log(f'Generated single fault circuit: {name} with fault on ({op.name}, wire:{wire}), theta = {theta}, phi = {phi}')
            #print(qml.draw(transformed_qnode)())
            transformed_qnode()
            mycircuits.append(transformed_qnode)
            inj_info.append(wire)
            op_info.append(op.name)
            index_info.append(index)
        index = index + 1
    log(f"{len(mycircuits)} circuits generated\n")
    return mycircuits, op_info, inj_info, index_info

```

Also note the @partial() decorator at the following page does not work:

> **[qml.transforms.insert](https://docs.pennylane.ai/en/stable/code/api/pennylane.transforms.insert.html)**

I had to modify the code as follows:

```auto

import pennylane as qml
from functools import partial

dev = qml.device("default.mixed", wires=2)

#@partial(qml.transforms.insert, qml.AmplitudeDamping, 0.2, position="end")
#@qml.qnode(dev)
def f(w, x, y, z):
    qml.RX(w, wires=0)
    qml.RY(x, wires=1)
    qml.CNOT(wires=[0, 1])
    qml.RY(y, wires=0)
    qml.RX(z, wires=1)
    return qml.expval(qml.Z(0) @ qml.Z(1))

dev_noisy = qml.transforms.insert(dev, qml.AmplitudeDamping, 0.2, position="end")
qnode_noisy = qml.QNode(f, dev_noisy)
print(qnode_noisy(0.9, 0.4, 0.5, 0.6))
qml.about()

```

Output:

```auto
0.754846996885476
Name: PennyLane
Version: 0.36.0
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: https://github.com/PennyLaneAI/pennylane
Author: 
Author-email: 
License: Apache License 2.0
Location: /home/xxx/anaconda/envs/qufi2/lib/python3.9/site-packages
Requires: appdirs, autograd, autoray, cachetools, networkx, numpy, pennylane-lightning, requests, rustworkx, scipy, semantic-version, toml, typing-extensions
Required-by: PennyLane-qiskit, PennyLane_Lightning

Platform info: Linux-5.4.0-150-generic-x86_64-with-glibc2.27
Python version: 3.9.19
Numpy version: 1.23.5
Scipy version: 1.10.0
Installed devices:
- default.clifford (PennyLane-0.36.0)
- default.gaussian (PennyLane-0.36.0)
- default.mixed (PennyLane-0.36.0)
- default.qubit (PennyLane-0.36.0)
- default.qubit.autograd (PennyLane-0.36.0)
- default.qubit.jax (PennyLane-0.36.0)
- default.qubit.legacy (PennyLane-0.36.0)
- default.qubit.tf (PennyLane-0.36.0)
- default.qubit.torch (PennyLane-0.36.0)
- default.qutrit (PennyLane-0.36.0)
- default.qutrit.mixed (PennyLane-0.36.0)
- null.qubit (PennyLane-0.36.0)
- lightning.qubit (PennyLane-Lightning-0.36.0)
- 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)

```

---

<div class="post-metadata">

**Author:** ![CatalinaAlbornoz](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/catalinaalbornoz/32/1196_2.png) [@CatalinaAlbornoz](https://discuss.pennylane.ai/u/CatalinaAlbornoz)\
**Post date:** [May 11, 2024, 12:05am UTC](https://discuss.pennylane.ai/t/qml-device-error-with-qiskit-aer/4556/10 "2024-05-11T00:05:38Z")

</div>

Hi @art,

I’m glad to see that you fixed the deepcopy error!

I can confirm that the example [here](https://docs.pennylane.ai/en/stable/code/api/pennylane.transforms.insert.html) isn’t working. Thank you for reporting it! I’ll let you know about the teams’ response to this next week.

I’m glad that you managed to modify the code to make it work. Let me know if you have any further questions and thank you again for reporting the error in the example!

---

<div class="post-metadata">

**Author:** ![art](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/art/32/1126_2.png) [@art](https://discuss.pennylane.ai/u/art)\
**Post date:** [May 13, 2024, 4:32am UTC](https://discuss.pennylane.ai/t/qml-device-error-with-qiskit-aer/4556/11 "2024-05-13T04:32:41Z")

</div>

@CatalinaAlbornoz how would I convert the qml.qfunc\_transform decorator to qml.transform for the pl\_insert\_gate() function (in injector.py)?

---

<div class="post-metadata">

**Author:** ![CatalinaAlbornoz](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/catalinaalbornoz/32/1196_2.png) [@CatalinaAlbornoz](https://discuss.pennylane.ai/u/CatalinaAlbornoz)\
**Post date:** [May 13, 2024, 2:48pm UTC](https://discuss.pennylane.ai/t/qml-device-error-with-qiskit-aer/4556/12 "2024-05-13T14:48:10Z")

</div>

Hi @art, my colleague David has opened [this Pull Request](https://github.com/PennyLaneAI/pennylane/pull/5681/) to fix the examples you mentioned in the documentation.

I don’t know exactly what the pl\_insert\_gate() function in injector.py is doing but below is the working example which adds a single-qubit amplitude damping error channel to the circuit (so it becomes a noisy circuit).

```auto
import pennylane as qml
from functools import partial

dev = qml.device("default.mixed", wires=2)

@partial(qml.transforms.insert, op=qml.AmplitudeDamping, op_args=0.2, position="end")
@qml.qnode(dev)
def f(w, x, y, z):
  qml.RX(w, wires=0)
  qml.RY(x, wires=1)
  qml.CNOT(wires=[0, 1])
  qml.RY(y, wires=0)
  qml.RX(z, wires=1)
  return qml.expval(qml.Z(0) @ qml.Z(1))

f(0.9, 0.4, 0.5, 0.6)

```

---

<div class="post-metadata">

**Author:** ![art](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/art/32/1126_2.png) [@art](https://discuss.pennylane.ai/u/art)\
**Post date:** [May 14, 2024, 12:37am UTC](https://discuss.pennylane.ai/t/qml-device-error-with-qiskit-aer/4556/13 "2024-05-14T00:37:44Z")

</div>

@CatalinaAlbornoz can you make the qml.qfunc\_transform to qml.transform change for the code snippet in the “Transforms with parameters” section of the following page:

> **[How to write quantum function transforms in PennyLane | PennyLane Blog](https://pennylane.ai/blog/2021/08/how-to-write-quantum-function-transforms-in-pennylane/)**
>
> Quantum transforms are an exciting new feature of PennyLane. Learn how transforms can help you construct and manipulate quantum functions with ease!

The code I wrote:

```auto
import pennylane as qml
from pennylane.tape import QuantumTape
from typing import Sequence, Callable

@qml.transform
def overrotate_rx(tape: QuantumTape, overrot_angle=0) -> (Sequence[QuantumTape], Callable):
    for op in tape.operation + tape.measurements:
        if op.name == "RX":
            qml.RX(op.parameters[0] + overrot_angle, wires=op.wires)
        else:
            qml.apply(op)

def circuit(x):
    qml.RX(x, wires=0)
    qml.CNOT(wires=[0, 1])
    qml.CNOT(wires=[1, 2])
    qml.Hadamard(wires=2)
    return qml.expval(qml.PauliZ(0))

dev = qml.device('default.qubit', wires=3)
transformed_circuit = overrotate_rx(0.1)(circuit)
qnode = qml.QNode(transformed_circuit, dev)
qnode(0.3)
print(qml.draw(qnode)(0.3))

```

gives the following error:

```auto

transformed_circuit = overrotate_rx(0.1)(circuit)
  File "/home/xxx/anaconda/envs/qufi2/lib/python3.9/site-packages/pennylane/transforms/core/transform_dispatcher.py", line 137, in __call__
    raise TransformError(
pennylane.transforms.core.transform_dispatcher.TransformError: Decorating a QNode with @transform_fn(**transform_kwargs) has been removed. Please decorate with @functools.partial(transform_fn,**transform_kwargs) instead, or call the transform directly using qnode = transform_fn(qnode, **transform_kwargs). Visit the deprecations page for more details: https://docs.pennylane.ai/en/stable/development/deprecations.html#completed-deprecation-cycles

```

---

<div class="post-metadata">

**Author:** ![CatalinaAlbornoz](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/catalinaalbornoz/32/1196_2.png) [@CatalinaAlbornoz](https://discuss.pennylane.ai/u/CatalinaAlbornoz)\
**Post date:** [May 14, 2024, 4:20pm UTC](https://discuss.pennylane.ai/t/qml-device-error-with-qiskit-aer/4556/14 "2024-05-14T16:20:54Z")

</div>

Hi @art,

The blog is very old so it no longer contains the most recent way to use transforms. Below you can find a working example.

```auto
import pennylane as qml
from typing import Sequence, Callable
from pennylane.tape import QuantumTape

def overrotate_rx(tape: QuantumTape, overrot_angle=0) -> (Sequence[QuantumTape], Callable):

    operations = []
    for op in tape.operations:
        if op.name == "RX":
          operations.append(qml.RX(op.parameters[0]+overrot_angle, wires=op.wires))
        else:
          operations.append(op)

    new_tape = type(tape)(operations, tape.measurements, shots=tape.shots)

    def null_postprocessing(results):
        return results[0]
    
    return [new_tape], null_postprocessing

dev = qml.device("default.qubit")

@qml.qnode(device=dev)
def circuit(x):
    qml.RX(x, wires=0)
    qml.CNOT(wires=[0, 1])
    qml.CNOT(wires=[1, 2])
    qml.Hadamard(wires=2)
    return qml.expval(qml.PauliZ(0))

dispatched_transform = qml.transform(overrotate_rx)

transformed_qnode = dispatched_transform(circuit, overrot_angle=0.3)
qml.draw_mpl(circuit,decimals=1)(0.1)
qml.draw_mpl(transformed_qnode,decimals=1)(0.1)

```

I hope this helps!

---

<div class="post-metadata">

**Author:** ![art](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/art/32/1126_2.png) [@art](https://discuss.pennylane.ai/u/art)\
**Post date:** [May 14, 2024, 10:33pm UTC](https://discuss.pennylane.ai/t/qml-device-error-with-qiskit-aer/4556/15 "2024-05-14T22:33:21Z")

</div>

@CatalinaAlbornoz I have gotten past the transform errors in qufi/injector.py by following your example code. I am now getting a “DefaultQubit has no attribute ‘num\_wires’” error from pennylane’s device\_api.py as follows (line numbers would have changed if you are referring to the legacy qufi code):

```auto

Running circuits
Traceback (most recent call last):
  File "/media/xxx/C-UAS-DB1/QuFI/run_circuits.py", line 24, in <module>
    results_names = execute_over_range(circuits, angles, coupling_map=coupling_map, results_folder="./tmp/")
  File "/media/xxx/C-UAS-DB1/QuFI/qufi/injector.py", line 328, in execute_over_range
    pl_inject(s, noise=noise)
  File "/media/xxx/C-UAS-DB1/QuFI/qufi/injector.py", line 277, in pl_inject
    circuitStruct.update(run_circuits( circuitStruct['base_circuit'], circuitStruct['generated_circuits'], noise=noise))
  File "/media/xxx/C-UAS-DB1/QuFI/qufi/injector.py", line 79, in run_circuits
    gold_device = qml.device('default.qubit', wires=base_circuit.device.num_wires)
  File "/home/xxx/anaconda/envs/qufi2/lib/python3.9/site-packages/pennylane/devices/device_api.py", line 181, in __getattr__
    raise AttributeError(
AttributeError: DefaultQubit has no attribute 'num_wires'. You may be looking for a property or method present in the legacy device interface. Please consult the DefaultQubit documentation for an updated list of public properties and methods.

```

What should be done in this case? I came across a similar error posting:

> <https://github.com/XanaduAI/Xanadu-Quantum-Codebook/issues/63>
>
> \### Node number
> 
> Codercise F.2.1, Codercise F.2.3
> 
> \### Expected behavior
> 
> The co…de in F.2.1 and F.2.3
> 
> \`\`\`python
> bits = \[int(x) for x in np.binary\_repr(basis\_id, width=dev.num\_wires)\]
> \`\`\`
> 
> seems not work. This can be simply fixed by
> \`\`\`python
> bits = \[int(x) for x in np.binary\_repr(basis\_id, width=num\_wires)\]
> \`\`\`
> 
> \---
> 
> Another issue is in the right hand side panel, there is a figure
> !\[f2-qft2-no-swap-hand\](https://github.com/XanaduAI/Xanadu-Quantum-Codebook/assets/64962473/0987b930-2e1c-42e1-8433-6cbd1b6b9461)
> 
> I think the green and purple initial states (the $|x\_0\\rangle$ and the $|x\_1\\rangle$) should also be swapped in the figure. To make the circuit work in this figure, one can test the code by adding additional line
> \`\`\`python
> bits = \[int(x) for x in np.binary\_repr(basis\_id, width=num\_wires)\]
> 
> \# add this line to make initial state swapped
> bits = bits\[::-1\]
> 
> qml.BasisStatePreparation(bits, wires=\[0, 1\])
> \`\`\`
> 
> \### Actual behavior
> 
> The error pops up when using \`dev.num\_wires\`
> \`\`\`bash
> Error: 'DefaultQubit' object has no attribute 'num\_wires'
> \`\`\`
> 
> \### Additional information
> 
> \_No response\_
> 
> \### Source code
> 
> \_No response\_
> 
> \### Tracebacks
> 
> \_No response\_
> 
> \### Check other issues
> 
> \- \[X\] I have searched existing GitHub issues to make sure the issue does not already exist.

---

<div class="post-metadata">

**Author:** ![CatalinaAlbornoz](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/catalinaalbornoz/32/1196_2.png) [@CatalinaAlbornoz](https://discuss.pennylane.ai/u/CatalinaAlbornoz)\
**Post date:** [May 15, 2024, 12:22am UTC](https://discuss.pennylane.ai/t/qml-device-error-with-qiskit-aer/4556/16 "2024-05-15T00:22:39Z")

</div>

Hi @art ,

If you follow what the error message says you’ll notice that DefaultQubit no longer has a ‘num\_wires’ attribute. You can instead try using the [wires](https://docs.pennylane.ai/en/stable/code/api/pennylane.devices.DefaultQubit.html#pennylane.devices.DefaultQubit.wires) attribute, but please use it carefully since it’s a different attribute so you will need to debug on your own to ensure compatibility with your code.

---

<div class="post-metadata">

**Author:** ![art](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/art/32/1126_2.png) [@art](https://discuss.pennylane.ai/u/art)\
**Post date:** [May 15, 2024, 2:22am UTC](https://discuss.pennylane.ai/t/qml-device-error-with-qiskit-aer/4556/17 "2024-05-15T02:22:39Z")

</div>

num\_wires indicates length of an array of wires  
so base\_circuit.device.num\_wires should be  
replaced by len(base\_circuit.device.wires).  
Code runs with that change.

---

<div class="post-metadata">

**Author:** ![CatalinaAlbornoz](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/catalinaalbornoz/32/1196_2.png) [@CatalinaAlbornoz](https://discuss.pennylane.ai/u/CatalinaAlbornoz)\
**Post date:** [May 15, 2024, 10:07pm UTC](https://discuss.pennylane.ai/t/qml-device-error-with-qiskit-aer/4556/18 "2024-05-15T22:07:01Z")

</div>

It’s great to see that you could solve it @art !