pprop.gates.base module

This module defines Gate, the abstract base class for all quantum gates in the Pauli propagation framework.

class pprop.gates.base.Gate(qml_gate, wires, parameter=None)[source]

Bases: ABC

Abstract base class for all quantum gates.

Each concrete gate subclass stores a PennyLane operator instance for circuit drawing and a Heisenberg evolution rule used during Pauli propagation. The constructor validates that the number of wires and the presence or absence of a parameter are consistent with the PennyLane gate’s expectations.

Parameters:

  • qml_gate (pennylane.operation.Operation) – PennyLane gate class (not instance) corresponding to this gate. The constructor instantiates it with a placeholder parameter value of 1 (for parametrised gates) or without parameters (for non-parametrised gates).

  • wires (list[int]) – Qubit indices on which this gate acts.

  • parameter (float, int, optional) – If it is np.intp or np.integer it represents the tndex of \(\theta\) in the global parameter vector. If it is float, it is actually an assigned value to the gate. If it is None, the gate is non-parametrised.

qml_gate

Instantiated PennyLane operator, used for circuit drawing.

Type:

pennylane.operation.Operation

wires

Qubit indices on which this gate acts.

Type:

list[int]

parameter

Value of the parametrized gate if float, index into the global parameter vector if int, or None for non-parametrised gates.

Type:

int or None

Raises:

  • ValueError – If the number of wires does not match the gate’s requirement.

  • ValueError – If the gate expects more than one parameter (unsupported).

  • ValueError – If a parametrised gate is constructed without a parameter_index.

  • ValueError – If a non-parametrised gate is constructed with a parameter_index.

Parameters:

  • qml_gate (Operation)

  • wires (List[int])

  • parameter (Optional[int])

abstractmethod evolve(word, k1, k2)[source]

Heisenberg-evolve a Pauli word through this gate.

Computes \(G^\dagger\, P\, G\) for the Pauli word \(P\) encoded in word, where \(G\) is this gate. The result is returned as a PauliDict mapping each output Pauli word to its updated CoeffTerms.

Subclasses may return an empty PauliDict to signal that the evolved word has been truncated by a cutoff.

Parameters:

  • word (tuple[PauliOp, CoeffTerms]) – (pauliop, coeff_terms) pair representing the Pauli word to evolve and its current symbolic coefficient.

  • k1 (int or None) – Pauli weight cutoff. Evolved words whose weight exceeds k1 are discarded. None disables weight truncation.

  • k2 (int or None) – Frequency cutoff. Evolved terms whose trigonometric frequency exceeds k2 are discarded. None disables frequency truncation.

Returns:

The evolved Pauli word(s) with updated coefficients. May be empty if the result was truncated by k1 or k2.

Return type:

PauliDict