Core expectationsΒΆ

Module name: pennylane.expval

Submodule containing core quantum expectation values supported by PennyLane.

PennyLane also supports a collection of built-in quantum expectations, including both discrete-variable (DV) expectations as used in the qubit model, and continuous-variable (CV) expectations as used in the qumode model of quantum computation.

Here, we summarize the built-in expectations supported by PennyLane, as well as the conventions chosen for their implementation.


All quantum operations in PennyLane are top level; they can be accessed via qml.OperationName. Expectation values, however, are contained within the pennylane.expval, and are thus accessed via qml.expval.ExpectationName.


When writing a plugin device for PennyLane, make sure that your plugin supports as many of the PennyLane built-in expectations defined here as possible.

If the convention differs between the built-in PennyLane expectation and the corresponding expectation in the targeted framework, ensure that the conversion between the two conventions takes places automatically by the plugin device.