squlearn.observables.SingleProbability
- class squlearn.observables.SingleProbability(num_qubits: int, qubit: int = 0, one_state: bool = False, parameterized: bool = False)
Observable for measuring the probability of being in state 0 or 1 of a specified qubit.
Equation as the operator is implemented:
\[\hat{H} = 0.5(\hat{I}_i+\hat{Z}_i) (= \ket{0}\bra{0}_i) \qquad \text{or} \qquad \hat{H} = 0.5(\hat{I}_i-\hat{Z}_i) (= \ket{1}\bra{1}_i)\]Operator can be optionally parameterized.
- Parameters:
num_qubits (int) – Number of qubits.
qubit (int) – Qubit to measure the probability of.
one_state (bool) – If True, measure the probability of being in state 1, otherwise state 0 (default: False).
parameterized (bool) – If True, the operator is parameterized (default: false).
Attributes:
- num_qubits
Number of qubits.
- Type:
int
- num_parameters
Number of trainable parameters in the single Pauli operator.
- Type:
int
- qubit
Qubit to measure the probability of.
- Type:
int
- one_state
If True, measure the probability of being in state 1, otherwise state 0.
- Type:
bool
- parameterized
If True, the operator is parameterized.
- Type:
bool
Methods:
- generate_initial_parameters(ones: bool = True, seed: int | None = None) ndarray
Generates random parameters for the observable
- Parameters:
ones (bool) – If True, returns an array of ones (default: True)
seed (Union[int,None]) – Seed for the random number generator
- Returns:
The randomly generated parameters
- get_operator(parameters: ParameterVector | ndarray) SparsePauliOp
Returns Operator as a SparsePauliOp expression.
- Parameters:
parameters (Union[ParameterVector, np.ndarray]) – Vector of parameters used in the operator
- Returns:
StateFn expression of the observable.
- get_params(deep: bool = True) dict
Returns hyper-parameters and their values of the single probability operator.
- Parameters:
deep (bool) – If True, also the parameters for contained objects are returned (default=True).
- Returns:
Dictionary with hyper-parameters and values.
- get_pauli(parameters: ParameterVector | ndarray = None) SparsePauliOp
Function for generating the SparsePauliOp expression of the single probability operator.
- Parameters:
parameters (Union[ParameterVector, np.ndarray]) – Parameters of the single probability operator.
- Returns:
SparsePauliOp expression of the specified single probability operator.
- get_pauli_mapped(parameters: ParameterVector | ndarray) SparsePauliOp
Changes the operator to the physical qubits, set by
set_map().- Parameters:
parameters (Union[ParameterVector, np.ndarray]) – Vector of parameters used in the operator
- Returns:
Expectation operator in Qiskit’s SprasePauliOp class with qubits mapped to physical ones
- set_map(qubit_map: list | dict, num_all_qubits: int)
Function for setting a qubit mapping from physical qubits to the ones of the operator.
This function is necessary whenever the number of physical qubits are different from the operator definition, as for example when running on a real backend. The number of qubits in the system has to be larger than the number of qubits in the observable.
- Parameters:
qubit_map (Union[list, dict]) – A list or dictionary specifying which of the input qubits are mapped to the output qubits.
num_all_qubits (int) – The total number of qubits in the system.
- set_params(**params) None
Sets value of the operator hyper-parameters.
- Parameters:
params – Hyper-parameters and their values, e.g.
num_qubits=2.