circuit_knitting.utils.observable_grouping.observables_restricted_to_subsystem

observables_restricted_to_subsystem(qubits, global_observables, /)[source]

Restrict each observable to its support on a given subsystem.

A PauliList will be returned if a PauliList is provided; otherwise, a list[Pauli] will be returned.

Parameters:

  • qubits (Sequence[int]) – The qubits in a subsystem

  • global_observables (Sequence[Pauli] | PauliList) – The list of observables

Return type:

list[Pauli] | PauliList

Returns:

Each Pauli restricted to the subsystem.

>>> observables_restricted_to_subsystem([1, 3], PauliList(["IXYZ", "ZZXX"]))
PauliList(['IY', 'ZX'])