# Measurement and feedback for cooling heavy levitated particles in low frequency traps

## TL;DR

This paper explores a method for cooling levitated nanoparticles in low-frequency magnetic traps using measurement and feedback, aiming to achieve quantum ground states despite environmental heating challenges.

## Contribution

It demonstrates the potential of low-frequency magnetic traps for effective feedback control and quantum state preparation of levitated particles.

## Key findings

- Low-frequency traps are suitable for real-time feedback control.
- Optimal feedback can prepare motional states with quantum properties.
- The approach addresses environmental heating challenges.

## Abstract

We consider a possible route to ground state cooling of a levitated nanoparticle, magnetically trapped by a strong permanent magnet, using a combination of measurement and feedback. The trap frequency of this system is much lower than those involving trapped ions or nano-mechanical resonators. Minimisation of environmental heating is therefore challenging as it requires control of the system on a timescale comparable to the inverse of the trap frequency. We show that these traps are an excellent platform for performing optimal feedback control via real-time state estimation, for the preparation of motional states with measurable quantum properties.