Fidelity

class pulser.backend.Fidelity(state, *, evaluation_times=None, tag_suffix=None)

Bases: Observable

Stores the fidelity with a pure state at the evaluation times.

The fidelity uses the overlap between the given state and the state of the system at each evaluation time. For pure states, this corresponds to |<ψ|φ(t)>|^2 for the given state |ψ> and the state |φ(t)> obtained by time evolution.

Parameters:

• state (State) – The state |ψ>. Note that this must be of an appropriate type for the backend.

• evaluation_times (Sequence[float] | None, default: None) – The relative times at which to compute the fidelity. If left as None, uses the default_evaluation_times of the backend’s EmulationConfig.

• tag_suffix (str | None, default: None) – An optional suffix to append to the tag. Needed if multiple instances of the same observable are given to the same EmulationConfig.

Attributes

tag	Label for the observable, used to index the Results object.
uuid	A universal unique identifier for this instance.

Methods

apply

Calculates the observable to store in the Results.

Signatures

apply(*, state, **kwargs)

Calculates the observable to store in the Results.

Return type:

Any

property tag: str

Label for the observable, used to index the Results object.

Within a Results instance, all computed observables must have different tags.

Returns:

The tag of the observable.

property uuid: UUID

A universal unique identifier for this instance.