.. _research_atoms:

High-Precision Measurement with Thermal Atoms
=============================================

High-precision measurement with thermal atomic ensembles, e.g., alkali-metal vapor cells, are of great importance and practical use.
We focus on using atomic spins to sense weak magnetic fields (magnetometer) and weak rotation signals (gyroscope).
We develope experimental techniques and theoretical methdos to explore the underlying physics of atomic sensors and try to approach their ultimate sensitivity limit.
We are also interested in the quantum nature of the measurement process, and trying to improve the sensitivity with quantum resources.

Optical Pumping of Alkali-Metal Atoms
-------------------------------------

Alkali-metal atoms are optically pumped by exchanging angular momentum with circularly polarized laser beam.
The polarized atoms are used to make a magnetometer by detecting their spin precession in weak magnetic fields.

.. figure:: ./_static/opticalPump.png
   :width: 500px
   :align: center
   :alt: optical pumping

Spin-Exchange Pumping of Noble Gas Nuclear Spins
------------------------------------------------

The spin polarization is transfered to nuclear spins of noble gas atoms, e.g., Xe atoms.
The precession of the polarzied nuclear spins is affected by both magnetic fields and the rotation of the detection system.
Eliminating the magnetic field effect, we can measure the rotation of the detection system, which gives the gyroscope signal.

.. figure:: ./_static/spinExchangePump.png
   :width: 500px
   :align: center
   :alt: spin-exchange pumping