QuantumFunctionError

[josh]

Hi @EMY91,

In PennyLane, we support two main models of quantum computation:

• Discrete variables
  • This is the model simulated by 'default.qubit', as well as the qiskit, Forest, and ProjectQ plugins.
  • This model supports specific operations and expectation values:
    Click here for a full list of discrete operations
    Click here for a full list of discrete expectation values

• Continuous variables
  • This is the model simulated by 'default.gaussian', as well as the Strawberry Fields plugin.
  • This model supports specific operations and expectation values:
    Click here for a full list of discrete operations
    Click here for a full list of discrete expectation values

There are several important things to note here:

• You cannot mix continuous and discrete operations in the same QNode.
  In your case, you are using qml.Displacement (a continuous operation) as well as qml.RY (a discrete operation) and qml.expval.PauliZ (a discrete expectation)

• If the QNode device is a continuous device, you must use only continuous operations. Likewise, if your QNode device is a discrete device, you must use only discrete operations.
  For example, default.qubit can use qml.RY, but not qml.Displacement.

I hope that helps, let me know if you have any other questions.