squlearn.encoding_circuit.ChebyshevRx

class squlearn.encoding_circuit.ChebyshevRx(num_qubits: int, num_features: int, num_layers: int = 1, closed: bool = False, alpha: float = 4.0, nonlinearity: str = 'arccos')

Simple Chebyshev encoding circuit build from Rx gates

Example for 4 qubits, a 2 dimensional feature vector and 2 layers:

(Source code, png, hires.png, pdf)

../../_images/squlearn-encoding_circuit-ChebyshevRx-1.png
Parameters:

  • num_qubits (int) – Number of qubits of the ChebyshevRx encoding circuit

  • num_features (int) – Dimension of the feature vector

  • num_layers (int) – Number of layers (default: 1)

  • closed (bool) – If true, the last and the first qubit are entangled (default: false)

  • alpha (float) – Maximum value of the Chebyshev Tower initial parameters, i.e. parameters that appear in the arccos encoding. (default: 4.0)

  • nonlinearity (str) – Mapping function to use for the feature encoding. Either arccos or arctan (default: arccos)

compose(x, concatenate_features=True, concatenate_parameters=False)

Composition of encoding circuits with options for handling features and parameters

Number of qubits and features have to be equal in both encoding circuits! The special function and properties of the both encoding circuits are lost by this composition.

Parameters:
Returns:

Returns the composed encoding circuit as special class ComposedEncodingCircuit

draw(output: str = None, feature_label: str = 'x', parameter_label: str = 'p', decompose: bool = False, **kwargs) → None

Draws the encoding circuit circuit using the QuantumCircuit.draw() function.

Parameters:

  • feature_label (str) – Label for the feature vector (default:”x”).

  • parameter_label (str) – Label for the parameter vector (default:”p”).

  • decompose (bool) – If True, the circuit is decomposed before printing (default: False).

  • kwargs – Additional arguments from Qiskit’s QuantumCircuit.draw() function.

Returns:

Returns the circuit in qiskit QuantumCircuit.draw() format

generate_initial_parameters(seed: int | None = None) → ndarray

Generates random parameters for the ChebyshevPQC encoding circuit

Parameters:

seed (Union[int,None]) – Seed for the random number generator (default: None)

Returns:

The randomly generated parameters

get_cheb_indices(flatten: bool = True)

Function that returns the indices of the parameters involved in the Chebyshev encoding.

Parameters:

flatten (bool) – If true, the indices are returned as a flat list, otherwise as a list of lists, where the outer list corresponds to the layers (default: True)

get_circuit(features: ParameterVector | ndarray, parameters: ParameterVector | ndarray) → QuantumCircuit

Returns the circuit of the ChebyshevRx encoding circuit

Parameters:

  • Union[ParameterVector (param_vec) – Input vector of the features from which the gate inputs are obtained

  • np.ndarray] – Input vector of the features from which the gate inputs are obtained

  • Union[ParameterVector – Input vector of the parameters from which the gate inputs are obtained

  • np.ndarray] – Input vector of the parameters from which the gate inputs are obtained

Returns:

Returns the circuit in Qiskit’s QuantumCircuit format

get_params(deep: bool = True) → dict

Returns hyper-parameters and their values of the ChebyshevRx encoding circuit

Parameters:

deep (bool) – If True, also the parameters for contained objects are returned (default=True).

Returns:

Dictionary with hyper-parameters and values.

inverse()

Returns the inverse of the encoding circuit.

Returns:

The inverse of the encoding circuit

set_params(**kwargs) → ChebyshevRx

Sets value of the encoding circuit hyper-parameters.

Parameters:

params – Hyper-parameters and their values, e.g. num_qubits=2.