Operator

class pulser.backend.Operator

Bases: ABC, Generic[ArgScalarType, ReturnScalarType, StateType]

Base class enforcing an API for quantum operator.

Each backend will implement its own type of state and the methods below.

Methods

apply_to	Apply the operator to a state.
expect	Compute the expectation value of self on the given state.
from_operator_repr	Create an operator from the operator representation.

Signatures

abstract apply_to(state, /)

Apply the operator to a state.

Parameters:

state (TypeVar(StateType, bound= State)) – The state to apply this operator to.

Return type:

TypeVar(StateType, bound= State)

Returns:

The resulting state.

abstract expect(state, /)

Compute the expectation value of self on the given state.

Parameters:

state (TypeVar(StateType, bound= State)) – The state with which to compute.

Return type:

TypeVar(ReturnScalarType)

Returns:

The expectation value.

classmethod from_operator_repr(*, eigenstates, n_qudits, operations)

Create an operator from the operator representation.

Only operators constructed with this method are allowed in remote backend.

The full operator representation (FullOp) is a weigthed sum of tensor operators (TensorOp), written as a sequence of coefficient and tensor operator pairs, ie

FullOp = Sequence[tuple[ScalarType, TensorOp]]

Each TensorOp is itself a sequence of qudit operators (QuditOp) applied to mutually exclusive sets of qudits (represented by their indices), ie

TensorOp = Sequence[tuple[QuditOp, Collection[int]]]

Qudits without an associated QuditOp are applied the identity operator.

Finally, each QuditOp is represented as weighted sum of pre-defined single-qudit operators. It is given as a mapping between a string representation of the single-qudit operator and its respective coefficient, ie

QuditOp = Mapping[str, ScalarType]

By default it identifies strings "ij" as single-qudit operators, where i and j are eigenstates that denote |i><j|.

Parameters:

• eigenstates (Sequence[Literal['u', 'd', 'r', 'g', 'h', 'x'] | Literal['0', '1']]) – The eigenstates to use.

• n_qubits – How many qubits there are in the system.

• operations (Sequence[tuple[TypeVar(ArgScalarType), Sequence[tuple[Mapping[str, TypeVar(ArgScalarType)], Collection[int]]]]]) – The full operator representation.

Return type:

TypeVar(OperatorType, bound= Operator)

Returns:

The constructed operator.