Device default.qubits does not exist. Make sure the required plugin is installed

PennyLane Help
1

Please help me solving this device error for default.qubits

import pennylane as qml
from pennylane import numpy as np
from pennylane import qchem
symbols = ["H", "H"]
coordinates = np.array([[-0.673, 0, 0], [0.673, 0, 0]])
hamiltonian, qubits = qchem.molecular_hamiltonian(symbols, coordinates)
print(qubits)

num_wires = qubits
dev = qml.device("default.qubits", wires = num_wires)

@qml.qnode(dev)
def exp_energy(state):
    qml.BasisState(np.array(state), wires = range(num_wires))
    return qml.expval(hamiltonian)```

If you want help with diagnosing an error, please put the full error message below:

DeviceError Traceback (most recent call last)
Cell In[7], line 2
1 num_wires = qubits
----> 2 dev = qml.device(“default.qubits”, wires = num_wires)
4 @qml.qnode(dev)
5 def exp_energy(state):
6 qml.BasisState(np.array(state), wires = range(num_wires))

File ~\anaconda3\Lib\site-packages\pennylane_init_.py:338, in device(name, *args, **kwargs)
334 dev.custom_expand(custom_decomp_expand_fn)
336 return dev
→ 338 raise DeviceError(“Device does not exist. Make sure the required plugin is installed.”)

DeviceError: Device does not exist. Make sure the required plugin is installed.

And, finally, make sure to include the versions of your packages. Specifically, show us the output of `qml.about()`.
2

Hello @Lis ! Welcome to the forum!

You have a tiny tiny typo in your code: the name of the device is default_qubit, without “s” in the end. :slight_smile:

3

yeah! I got it corrected…><

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