Problem charging forest device



I’m doing the serie of tutorials, to learn a bit about PennyLane.
So far everything was working just fine, but then I tried the PyTorch tutorial, which start by using a forest devices. I installed the forest software and the plugin, however when I run :

import pennylane as qml
import torch
from torch.autograd import Variable
dev = qml.device('forest.qvm', device='2q', noisy=True)

I get the following error:

AttributeError                            Traceback (most recent call last)
<ipython-input-2-2cf089c8119a> in <module>
----> 1 dev = qml.device('forest.qvm', device='2q', noisy=True)

~\.conda\envs\penny\lib\site-packages\pennylane\ in device(name, *args, **kwargs)
    211         # load plugin device
--> 212         return plugin_device_class(*args, **options)
    214     raise DeviceError('Device does not exist. Make sure the required plugin is installed.')

~\.conda\envs\penny\lib\site-packages\pennylane_forest\ in __init__(self, device, shots, noisy, **kwargs)
     91                              "a valid QVM quantum computer, or a NetworkX graph object.")
---> 93         super().__init__(num_wires, shots, **kwargs)
     95         # get the qc

~\.conda\envs\penny\lib\site-packages\pennylane_forest\ in __init__(self, wires, shots, **kwargs)
    187     def __init__(self, wires, shots, **kwargs):
    188         super().__init__(wires, shots)
--> 189         self.forest_url = kwargs.get('forest_url', pyquil_config.compiler_url)
    190         self.qvm_url = kwargs.get('qvm_url', pyquil_config.qvm_url)
    191         self.compiler_url = kwargs.get('compiler_url', pyquil_config.compiler_url)

AttributeError: 'PyquilConfig' object has no attribute 'compiler_url'

I have to admit that I have no idea how to solve it, so any help would be welcome.

All the best,



Hi barthelemymp,

There are breaking changes in the latest versions of Rigetti software, and it affects PennyLane. I’m not sure if this is the same issue (@josh knows this better – perhaps he can comment), but we are working with Rigetti to fix the plugin.



Hi @barthelemymp, thank you for flagging this! I will take a look and see if I can reproduce the bug.

Can I ask you to run the following three commands, to determine the versions of quilc, QVM, and PyQuil you are using:

quilc --version
qvm --version
python -c "import pyquil; print(pyquil.__version__)"


Hello Josh

Here are the results from the code you asked:

quilc --version
1.6.0 [1d29de5]

qvm --version
1.6.0 [26b5bd8]

python -c "import pyquil; print(pyquil.__version__)"

For this one, It was on the conda environnement I created for penny lane. Maybe there is a problem related the conda environment? Penny lane and the forest plugin are only installed on the envs…

Best regards



Hi @barthelemymp,

I was able to reproduce the error using the version of PennyLane-Forest installed via pip.

This bug is currently fixed in the latest GitHub master branch of PennyLane-Forest. I will update the pip version so this bug is fixed for users that pip install pennylane-forest ASAP, thank you for letting us know!

In the meantime, you can switch to the GitHub development version as follows:

git clone
cd pennylane-forest && pip install -e .

After running those above two commands, the tutorial linked above should work without error.