braket.circuits.observable module

class braket.circuits.observable.Observable(qubit_count: int, ascii_symbols: Sequence[str])[source]

Bases: QuantumOperator

Class Observable to represent a quantum observable.

Objects of this type can be used as input to ResultType.Sample, ResultType.Variance, ResultType.Expectation to specify the measurement basis.

Initializes a QuantumOperator.

Parameters:

qubit_count (Optional[int]) – Number of qubits this quantum operator acts on. If all instances of the operator act on the same number of qubits, this argument should be None, and fixed_qubit_count should be implemented to return the qubit count; if fixed_qubit_count is implemented and an int is passed in, it must equal fixed_qubit_count, or instantiation will raise a ValueError. An int must be passed in if instances can have a varying number of qubits, in which case fixed_qubit_count should not be implemented,
ascii_symbols (Sequence[str]) – ASCII string symbols for the quantum operator. These are used when printing a diagram of circuits. Length must be the same as qubit_count, and index ordering is expected to correlate with target ordering on the instruction. For instance, if CNOT instruction has the control qubit on the first index and target qubit on the second index. Then ASCII symbols would have [“C”, “X”] to correlate a symbol with that index.

Raises:

TypeError – qubit_count is not an int
ValueError – qubit_count is less than 1, ascii_symbols are None, fixed_qubit_count is implemented and and not equal to qubit_count, or len(ascii_symbols) != qubit_count

to_ir(target: QubitSet | None = None, ir_type: IRType = IRType.JAQCD, serialization_properties: SerializationProperties | None = None) → str | list[str | list[list[list[float]]]][source]

Returns the IR representation for the observable

Parameters:

target (QubitSet | None) – target qubit(s). Defaults to None.
ir_type (IRType) – The IRType to use for converting the result type object to its IR representation. Defaults to IRType.JAQCD.
serialization_properties (SerializationProperties | None) – The serialization properties to use while serializing the object to the IR representation. The serialization properties supplied must correspond to the supplied ir_type. Defaults to None.

Returns:

Union[str, list[Union[str, list[list[list[float]]]]]] – The IR representation for the observable.

Raises:

ValueError – If the supplied ir_type is not supported, or if the supplied serialization properties don’t correspond to the ir_type.

property coefficient: int

The coefficient of the observable.

Returns:: int – coefficient value of the observable.

property basis_rotation_gates: tuple[Gate, ...]

Returns the basis rotation gates for this observable.

Returns:: tuple[Gate, …] – The basis rotation gates for this observable.

property eigenvalues: ndarray

Returns the eigenvalues of this observable.

Returns:: np.ndarray – The eigenvalues of this observable.

eigenvalue(index: int) → float[source]

Returns the eigenvalue of this observable at the given index.

The eigenvalues are ordered by their corresponding computational basis state after diagonalization.

Parameters:: index (int) – The index of the desired eigenvalue
Returns:: float – The index th eigenvalue of the observable.

classmethod register_observable(observable: Observable) → None[source]

Register an observable implementation by adding it into the Observable class.

Parameters:: observable (Observable) – Observable class to register.

class H

Bases: StandardObservable

Hadamard operation as an observable.

Examples: >>> Observable.H()

property basis_rotation_gates: tuple[Gate, ...]

Returns the basis rotation gates for this observable.

Returns:: tuple[Gate, …] – The basis rotation gates for this observable.

to_matrix() → ndarray

Returns a matrix representation of the quantum operator.

Parameters:

*args (Any) – Not Implemented.
**kwargs (Any) – Not Implemented.

Raises:

NotImplementError – Not Implemented.

Returns:

np.ndarray – A matrix representation of the quantum operator

class Hermitian(matrix: ndarray, display_name: str = 'Hermitian')

Bases: Observable

Hermitian matrix as an observable.

Inits a Hermitian.

Parameters:

matrix (np.ndarray) – Hermitian matrix that defines the observable.
display_name (str) – Name to use for an instance of this Hermitian matrix observable for circuit diagrams. Defaults to Hermitian.

Raises:

ValueError – If matrix is not a two-dimensional square matrix, or has a dimension length that is not a positive power of 2, or is not Hermitian.

Examples

>>> Observable.Hermitian(matrix=np.array([[0, 1],[1, 0]]))

property basis_rotation_gates: tuple[Gate, ...]

Returns the basis rotation gates for this observable.

Returns:: tuple[Gate, …] – The basis rotation gates for this observable.

eigenvalue(index: int) → float

Returns the eigenvalue of this observable at the given index.

The eigenvalues are ordered by their corresponding computational basis state after diagonalization.

Parameters:: index (int) – The index of the desired eigenvalue
Returns:: float – The index th eigenvalue of the observable.

property eigenvalues: ndarray

Returns the eigenvalues of this observable.

Returns:: np.ndarray – The eigenvalues of this observable.

to_matrix() → ndarray

Returns a matrix representation of the quantum operator.

Parameters:

*args (Any) – Not Implemented.
**kwargs (Any) – Not Implemented.

Raises:

NotImplementError – Not Implemented.

Returns:

np.ndarray – A matrix representation of the quantum operator

class I

Bases: Observable

Identity operation as an observable.

Examples: >>> Observable.I()

property basis_rotation_gates: tuple[Gate, ...]

Returns the basis rotation gates for this observable.

Returns:: tuple[Gate, …] – The basis rotation gates for this observable.

eigenvalue(index: int) → float

Returns the eigenvalue of this observable at the given index.

The eigenvalues are ordered by their corresponding computational basis state after diagonalization.

Parameters:: index (int) – The index of the desired eigenvalue
Returns:: float – The index th eigenvalue of the observable.

property eigenvalues: ndarray

Returns the eigenvalues of this observable.

Returns:: np.ndarray – The eigenvalues of this observable.

to_matrix() → ndarray

Returns a matrix representation of the quantum operator.

Parameters:

*args (Any) – Not Implemented.
**kwargs (Any) – Not Implemented.

Raises:

NotImplementError – Not Implemented.

Returns:

np.ndarray – A matrix representation of the quantum operator

class Sum(observables: list[Observable], display_name: str = 'Hamiltonian')

Bases: Observable

Sum of observables

Inits a Sum.

Parameters:

observables (list[Observable]) – List of observables for Sum
display_name (str) – Name to use for an instance of this Sum observable for circuit diagrams. Defaults to Hamiltonian.

Examples

>>> t1 = -3 * Observable.Y() + 2 * Observable.X()
Sum(X('qubit_count': 1), Y('qubit_count': 1))
>>> t1.summands
(X('qubit_count': 1), Y('qubit_count': 1))

property basis_rotation_gates: tuple[Gate, ...]

Returns the basis rotation gates for this observable.

Returns:: tuple[Gate, …] – The basis rotation gates for this observable.

eigenvalue(index: int) → float

Returns the eigenvalue of this observable at the given index.

The eigenvalues are ordered by their corresponding computational basis state after diagonalization.

Parameters:: index (int) – The index of the desired eigenvalue
Returns:: float – The index th eigenvalue of the observable.

property eigenvalues: ndarray

Returns the eigenvalues of this observable.

Returns:: np.ndarray – The eigenvalues of this observable.

property summands: tuple[Observable, ...]

The observables that comprise this sum.

Type:: tuple[Observable]

to_matrix() → ndarray

Returns a matrix representation of the quantum operator.

Parameters:

*args (Any) – Not Implemented.
**kwargs (Any) – Not Implemented.

Raises:

NotImplementError – Not Implemented.

Returns:

np.ndarray – A matrix representation of the quantum operator

class TensorProduct(observables: list[Observable])

Bases: Observable

Tensor product of observables

Initializes a TensorProduct.

Parameters:: observables (list[Observable]) – List of observables for tensor product

Examples

>>> t1 = Observable.Y() @ Observable.X()
>>> t1.to_matrix()
array([[0.+0.j, 0.+0.j, 0.-0.j, 0.-1.j],
[0.+0.j, 0.+0.j, 0.-1.j, 0.-0.j],
[0.+0.j, 0.+1.j, 0.+0.j, 0.+0.j],
[0.+1.j, 0.+0.j, 0.+0.j, 0.+0.j]])
>>> t2 = Observable.Z() @ t1
>>> t2.factors
(Z('qubit_count': 1), Y('qubit_count': 1), X('qubit_count': 1))

Note: You must provide the list of observables for the tensor product to be evaluated in the order that you want the tensor product to be calculated. For TensorProduct(observables=[ob1, ob2, ob3]), the tensor product’s matrix is the result of the tensor product of ob1, ob2, ob3, or np.kron(np.kron(ob1.to_matrix(), ob2.to_matrix()), ob3.to_matrix()).

property ascii_symbols: tuple[str, ...]

Returns the ascii symbols for the quantum operator.

Type:: tuple[str, …]

property basis_rotation_gates: tuple[Gate, ...]

Returns the basis rotation gates for this observable.

Returns:: tuple[Gate, …] – The basis rotation gates for this observable.

eigenvalue(index: int) → float

Returns the eigenvalue of this observable at the given index.

The eigenvalues are ordered by their corresponding computational basis state after diagonalization.

Parameters:: index (int) – The index of the desired eigenvalue
Returns:: float – The index th eigenvalue of the observable.

property eigenvalues: ndarray

Returns the eigenvalues of this observable.

Returns:: np.ndarray – The eigenvalues of this observable.

property factors: tuple[Observable, ...]

The observables that comprise this tensor product.

Type:: tuple[Observable]

to_matrix() → ndarray

Returns a matrix representation of the quantum operator.

Parameters:

*args (Any) – Not Implemented.
**kwargs (Any) – Not Implemented.

Raises:

NotImplementError – Not Implemented.

Returns:

np.ndarray – A matrix representation of the quantum operator

class X

Bases: StandardObservable

Pauli-X operation as an observable.

Examples: >>> Observable.X()

property basis_rotation_gates: tuple[Gate, ...]

Returns the basis rotation gates for this observable.

Returns:: tuple[Gate, …] – The basis rotation gates for this observable.

to_matrix() → ndarray

Returns a matrix representation of the quantum operator.

Parameters:

*args (Any) – Not Implemented.
**kwargs (Any) – Not Implemented.

Raises:

NotImplementError – Not Implemented.

Returns:

np.ndarray – A matrix representation of the quantum operator

class Y

Bases: StandardObservable

Pauli-Y operation as an observable.

Examples: >>> Observable.Y()

property basis_rotation_gates: tuple[Gate, ...]

Returns the basis rotation gates for this observable.

Returns:: tuple[Gate, …] – The basis rotation gates for this observable.

to_matrix() → ndarray

Returns a matrix representation of the quantum operator.

Parameters:

*args (Any) – Not Implemented.
**kwargs (Any) – Not Implemented.

Raises:

NotImplementError – Not Implemented.

Returns:

np.ndarray – A matrix representation of the quantum operator

class Z

Bases: StandardObservable

Pauli-Z operation as an observable.

Examples: >>> Observable.Z()

property basis_rotation_gates: tuple[Gate, ...]

Returns the basis rotation gates for this observable.

Returns:: tuple[Gate, …] – The basis rotation gates for this observable.

to_matrix() → ndarray

Returns a matrix representation of the quantum operator.

Parameters:

*args (Any) – Not Implemented.
**kwargs (Any) – Not Implemented.

Raises:

NotImplementError – Not Implemented.

Returns:

np.ndarray – A matrix representation of the quantum operator

class braket.circuits.observable.StandardObservable(ascii_symbols: Sequence[str])[source]

Bases: Observable

Class StandardObservable to represent a Pauli-like quantum observable with eigenvalues of (+1, -1).

Initializes a QuantumOperator.

Parameters:

qubit_count (Optional[int]) – Number of qubits this quantum operator acts on. If all instances of the operator act on the same number of qubits, this argument should be None, and fixed_qubit_count should be implemented to return the qubit count; if fixed_qubit_count is implemented and an int is passed in, it must equal fixed_qubit_count, or instantiation will raise a ValueError. An int must be passed in if instances can have a varying number of qubits, in which case fixed_qubit_count should not be implemented,
ascii_symbols (Sequence[str]) – ASCII string symbols for the quantum operator. These are used when printing a diagram of circuits. Length must be the same as qubit_count, and index ordering is expected to correlate with target ordering on the instruction. For instance, if CNOT instruction has the control qubit on the first index and target qubit on the second index. Then ASCII symbols would have [“C”, “X”] to correlate a symbol with that index.

Raises:

TypeError – qubit_count is not an int
ValueError – qubit_count is less than 1, ascii_symbols are None, fixed_qubit_count is implemented and and not equal to qubit_count, or len(ascii_symbols) != qubit_count

property eigenvalues: ndarray

Returns the eigenvalues of this observable.

Returns:: np.ndarray – The eigenvalues of this observable.

eigenvalue(index: int) → float[source]

Returns the eigenvalue of this observable at the given index.

The eigenvalues are ordered by their corresponding computational basis state after diagonalization.

Parameters:: index (int) – The index of the desired eigenvalue
Returns:: float – The index th eigenvalue of the observable.

property ascii_symbols: tuple[str, ...]

Returns the ascii symbols for the quantum operator.

Type:: tuple[str, …]