squlearn.encoding_circuit.HubregtsenEncodingCircuit

class squlearn.encoding_circuit.HubregtsenEncodingCircuit(num_qubits: int, num_features: int, num_layers: int = 1, closed: bool = True, final_encoding=False)

Creates the data reuploading encoding circuit as presented in reference [1].

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

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

../../_images/squlearn-encoding_circuit-HubregtsenEncodingCircuit-1.png

The encoding can be optionally repeated at the end to make the previous rotations not redundant in a fidelity kernel setting. The circuit is closed by default, i.e. the last qubit is entangled with the first one.

Parameters:

  • num_qubits (int) – Number of qubits of the 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; not necessarily hardware efficient! (default: true)

  • final_encoding (bool) – If True, the encoding is repeated at the end (default: False)

References

[1]: T. Hubregtsen et al., “Training Quantum Embedding Kernels on Near-Term Quantum Computers”, arXiv:2105.02276v1 (2021).

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 encoding circuit

Parameters:

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

Returns:

The randomly generated parameters

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

Generates and returns the circuit of the Hubregtsen encoding circuit

Parameters:

  • features (Union[ParameterVector,np.ndarray]) – Input vector of the features from which the gate inputs are obtained.

  • param_vec (Union[ParameterVector,np.ndarray]) – Input vector of the parameters from which the gate inputs are obtained.

Returns:

Returns the Hubregtsen circuit in qiskit QuantumCircuit format

get_params(deep: bool = True) → dict

Returns hyper-parameters and their values of the Hubregtsen 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(**params) → EncodingCircuitBase

Sets value of the encoding circuit hyper-parameters.

Parameters:

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