# Ultra-low noise magnetic field for quantum gases

## TL;DR

This paper demonstrates a method to stabilize a bias magnetic field at 14.5G with ultra-low noise and high stability, crucial for quantum experiments involving ultra-cold atoms and Bose-Einstein condensates.

## Contribution

The study introduces a combined approach using μ-metal magnetic shields and a dynamical feedback circuit to achieve ultra-low noise magnetic fields with high stability.

## Key findings

- RMS noise reduced to 18.5 μG (1.28 ppm)
- Long-term instability below 7 μG
- Enhanced coherence time of Bose-Einstein condensate

## Abstract

Ultra-low noise magnetic field is essential for many branches of scientific research. Examplesinclude experiments conducted on ultra-cold atoms, quantum simulations, as well as precisionmeasurements. In ultra-cold atom experiments specifically, a bias magnetic field will be oftenserved as a quantization axis and be applied for Zeeman splitting. As atomic states areusually sensitive to magnetic fields, a magnetic field characterized by ultra-low noise as wellas high stability is typically required for experimentation. For this study, a bias magneticfield is successfully stabilized at 14.5G, with the root mean square (RMS) value of the noisereduced to 18.5{\mu}G (1.28ppm) by placing{\mu}-metal magnetic shields together with a dynamicalfeedback circuit. Long-time instability is also regulated consistently below 7{\mu}G. The level ofnoise exhibited in the bias magnetic field is further confirmed by evaluating the coherencetime of a Bose-Einstein condensate characterized by Rabi oscillation. It is concluded thatthis approach can be applied to other physical systems as well.