LayerModel

class LayerModel(L, H2, H1=None, cyclic=False, keep_only_odd=None)[source]

Bases: LocalHam1D

A model for representing a layer of time-evolution interactions.

Essentially, this class is a simple wrapper of quimb.tensor.LocalHam1D. Its main purpose is to provide a simple interface for constructing a Quimb-compatible Hamiltonian from Qiskit objects.

Initialize a LayerModel instance.

Most of the arguments below are simply forwarded to quimb.tensor.LocalHam1D so check out its documentation for more details.

Parameters:

  • L – the number of qubits.

  • H2 – the two-site interactions.

  • H1 – the optional on-site interactions.

  • cyclic – whether to apply periodic boundary conditions.

  • keep_only_odd – whether to keep only odd bond interactions. For more details see keep_only_odd.

Attributes

keep_only_odd

Whether to keep only interactions on bonds with odd indices.

Methods

classmethod from_quantum_circuit(circuit, *, scaling_factor=1.0, keep_only_odd=None, **kwargs)[source]

Construct a LayerModel from a QuantumCircuit.

You can see an example of this function in action in the docs of quimb_layers.

Parameters:

  • circuit (QuantumCircuit) – the quantum circuit to parse.

  • scaling_factor (float) – a factor with which to scale the term strengths. This can be used to apply (for example) a time step scaling factor. It may also be used (e.g.) to split onsite terms into two layers (even and odd) with $0.5$ of the strength, each.

  • keep_only_odd (bool | None) – the value to use for keep_only_odd.

  • kwargs – any additional keyword arguments to pass to the LayerModel constructor.

Returns:

A new LayerModel instance.

Raises:

NotImplementedError – if an unsupported quantum gate is encountered.

Return type:

LayerModel

get_gate_expm(where, x)[source]

Get the local term at the sites where, matrix exponentiated by x.

If where applies to an even bond index and keep_only_odd is True, this method will return None.

Parameters:

  • where (tuple[int, int]) – the pair of site indices of the local term to get. This identifies the bond index.

  • x (float) – the value with which to matrix exponentiate the interaction term.

Returns:

The interaction in terms of an array or None depending on keep_only_odd (see above).

Return type:

ndarray | None