squlearn.observables.SummedProbabilities
- class squlearn.observables.SummedProbabilities(num_qubits: int, one_state=False, full_sum: bool = True, include_identity: bool = True)
Observable for summing single Qubit probabilities of binary states.
Equation for a sum of 0-states:
\[\hat{H} = a\hat{I} + \sum_i b_i (\ket{0}\bra{0})_i\]States are implemented by \(\ket{0}\bra{0} = 0.5(\hat{I}+\hat{Z})\) and \(\ket{1}\bra{1} = 0.5(\hat{I}-\hat{Z})\).
The parameter can be optionally equal for all states.
- Parameters:
num_qubits (int) – Number of qubits.
one_state (bool) – If false the \(\ket{0}\bra{0}\) state is measured, if true the \(\ket{1}\bra{1}\) state is measured (default: False).
full_sum (bool) – If False, the parameter is the same for all states, i.e. the sum is \(b\sum_i (\ket{0}\bra{0})_i\) instead of \(\sum_i b_i (\ket{0}\bra{0})_i\) (default: True).
include_identity (bool) – If True, the identity operator is included in the sum. (default: True)
Attributes:
- num_qubits
Number of qubits.
- Type:
int
- num_parameters
Number of trainable parameters in the summed probabilities operator.
- Type:
int
- one_state
If false the \(\ket{0}\bra{0}\) state is measured, if true the \(\ket{1}\bra{1}\) state is measured.
- Type:
bool
- full_sum
If False, the parameter is the same for all states.
- Type:
bool
- include_identity
If True, the identity operator is included in the sum.
- 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 summed probabilities 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 PauliOp expression of the summed probabilities operator.
- Parameters:
parameters (Union[ParameterVector, np.ndarray]) – Parameters of the summed probabilities operator.
- Returns:
PauliOp expression of the specified summed probabilities 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.