# Achieving Heisenberg limit under General Markov Noise without Ancilla

## TL;DR

This paper demonstrates that the Heisenberg limit in quantum metrology can be achieved under general Markovian noise without using ancillas, by applying full and rapid control when the Hamiltonian has a perpendicular component to the noise.

## Contribution

It shows that Heisenberg limit can be restored under Markovian noise without ancillas, given specific Hamiltonian conditions, using full and fast control.

## Key findings

- Heisenberg limit achievable without ancillas under Markovian noise
- Full and fast control restores quantum precision limits
- Perpendicular Hamiltonian component is crucial for HL achievement

## Abstract

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