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)

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.

set_params(**kwargs) → ChebyshevRx

Sets value of the encoding circuit hyper-parameters.

Parameters:

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