Source code for mpstab.engines.tensor_networks.native

from __future__ import annotations

from typing import Any

from mpstab.engines.tensor_networks.abstract import TensorNetworkEngine
from mpstab.evolutors.tensor_network.circuit_mps import CircuitMPS
from mpstab.evolutors.tensor_network.operators.observables import PauliMPO




class NativeTensorNetworkEngine(TensorNetworkEngine):
    """
    Thin adapter that exposes the minimal API required by HybridSurrogate
    while reusing the existing evolutors.tensor_network implementation.
    """



    def build_circuit_mps(
        self,
        n: int,
        initial_state_amplitudes: Any,
        initial_state_circuit: Any,
        max_bond_dimension: int | None = None,
    ):
        """
        Create a CircuitMPS initialised with `initial_state`.
        `initial_state` is passed as-is to CircuitMPS (the caller creates the
        array of single-qubit amplitudes as before).
        """
        return CircuitMPS(
            n=n,
            initial_state=initial_state_amplitudes,
            max_bond_dimension=max_bond_dimension,
        )




    def pauli_mpo(self, pauli_string: str | object):
        """Return the existing PauliMPO for the given pauli_string."""
        return PauliMPO(pauli_string)




    def expval(self, state_circuit: CircuitMPS, operator: PauliMPO):
        """Compute the expectation value of `operator` on `state`."""
        return state_circuit.expval(operator)




    def pauli_rot(
        self,
        state_circuit: CircuitMPS,
        generator: str,
        angle: float,
        max_bond_dimension: int,
    ):
        """Apply a Pauli rotation specified by `generator` and `angle` to the MPS."""
        return state_circuit.pauli_rot(generator, angle)