We consider probing qubits infested by general Makovian noise. It can be shown that one can restore Heisenberg limit (HL) via full and fast control without any ancilla, as long as the Hamiltonian of the system has non-vanishing component perpendicular to the noise
@article{arxiv.1903.07888,
title = {Achieving Heisenberg limit under General Markov Noise without Ancilla},
author = {Yi Peng and Heng Fan},
journal= {arXiv preprint arXiv:1903.07888},
year = {2023}
}