Precision measurements of spin interactions with high density atomic vapors

Iannis K. Kominis

Spin noise sets fundamental limits to the precision of measurements using spin-polarized atomic vapors, such as performed with sensitive atomic magnetometers. Spin squeezing offers the possibility to extend the measurement precision beyond the standard quantum limit of uncorrelated atoms. Contrary to current understanding, we show that, even in the presence of spin relaxation, spin squeezing can lead to a significant reduction of spin noise, and hence an increase in magnetometric sensitivity, for a long measurement time. This is the case when correlated spin relaxation due to binary alkali-atom collisions dominates independently acting decoherence processes, a situation realized in thermal high atom-density magnetometers and clocks.

Robert E. Tench

Shuguang Li, Pengfeng Dai, Jinsheng Liu +2 more

Optically-dense alkali-metal vapor cells with low optical losses are widely used in quantum precision measurements, yet atomic behaviors in coated cells still need further study. We developed an octadecyltrichlorosilane (OTS) anti-relaxation and dielectric anti-reflection coated multipass optical cell filled with rubidium vapor at high density, and investigated the spin relaxation as well as the spin noise of the atomic ensembles. High contrast spin noise spectrum was observed and we find that the quantum coherence lifetime is equal to the classical transverse spin relaxation time. Number density measurements give the spin-exchange possibility of 14% between rubidium atoms trapped in the coating.

Edwin Albert Power, William J. Meath, Joseph O. Hirschfelder

Donghui Ma, HE Xinxin, HUA Zeyu +7 more

With the state-of-the-art quantum measurement devices, such as atomic clocks, atomic gyroscopes, and atomic magnetometers, as their central components, the spatiotemporal evolution of atomic spin polarization in the atomic vapor cell has a major effect on both increasing the bandwidth of magnetometer and improving the accuracy of magnetic gradient measurements. However, the major factor impeding the further improvement of the performance of quantum measurement instrument is the inherent static nature of the traditional intra-vapor cell segmentation imaging technique, which makes it challenging to achieve the real-time capture of the dynamic evolution of atomic spin states. In this work, we suggest a dynamic spin imaging method for alkali metal atomic vapor cells with real-time modification of atomic spin polarization states in order to overcome this technological difficulty. In particular, to ensure that the laser can precisely act on the alkali metal atoms in various regions in the vapor cell, we employ a complex beam array management system to modify the on/off state of the laser beams at various positions in the spatial dimension in real time. In the meantime, we generate laser fields with particular spatial distribution and frequency characteristics by using frequency modulation techniques in the time series to accurately regulate the on-off frequency of each laser beam in the beam array. These laser beams cause dynamic changes in the atomic spin polarization state by interacting with alkali metal atoms at various points in the vapor cell. Through precise adjustment of the laser properties, we can see and study the dynamic evolution of the atomic spin-polarization state in real time. According to the experimental data, the technology outperforms the traditional static spin imaging techniques by achieving an excellent temporal resolution of 355 frames per second and a spatial resolution of 95.9 micrometers. The effective use of this method enables us to monitor and evaluate the dynamic aspects of magnetic field distribution with unprecedented precision, also greatly enhance our understanding of the dynamic characteristics of atomic spin polarization.

S. L. Gilbert, Bernard P. Masterson, Martin Charles Noecker +1 more