QuantumFunctionError: Invalid device

PennyLane Help
1

Hello!

I am trying to use a PennyLane device as follows:

Step 1: Define the Quantum Device

I start by defining my device:

# Define the quantum device
n_qubits = 5
dev = qml.device("lightning.qubit", wires=n_qubits)
print(dev)

Step 2: Create the Quantum Model Class

Next, I create a model class that accepts the device as a parameter:

class QuantumCell(nn.Module):
    def __init__(self, quantum_circuit, input_size, hidden_size, n_qubits, n_qlayers, device):
        super(QuantumCell, self).__init__()
        self.device = device
        # Additional initialization code...

Following this, I define a quantum model:

class QM(nn.Module):
    def __init__(self, quantum_circuit, input_size, hidden_size, n_qubits, n_qlayers, device, batch_first=True):
        super(QM, self).__init__()
        self.cell = QuantumCell(quantum_circuit, input_size, hidden_size, n_qubits, n_qlayers, device)
        # Additional initialization code...

Step 3: Instantiate the Model

Finally, I instantiate the quantum model:

# Create a Q model
model = QM(Basic_VQC_RZ, input_size, embedding_size, hidden_size, n_qubits, n_qlayers, dev)

Issue Encountered

However, when creating the model instance, I encounter the following error:

__init__(self, func, device, interface, diff_method, grad_on_execution, cache, cachesize, max_diff, device_vjp, postselect_mode, mcm_method, **gradient_kwargs)
    537 
    538         if not isinstance(device, (qml.devices.LegacyDevice, qml.devices.Device)):
--> 539             raise qml.QuantumFunctionError(
    540                 "Invalid device. Device must be a valid PennyLane device."
    541             )

QuantumFunctionError: Invalid device. Device must be a valid PennyLane device.

This error appears each time I create an instance of my model, even when using "lightning.qubit" or "default.qubit" devices.

Would you like help troubleshooting this issue or advice on debugging?