Enhancement of spin noise spectroscopy of rubidium atomic ensemble by using of the polarization squeezed light

TL;DR

This study enhances rubidium atomic spin noise spectroscopy by employing polarization squeezed light, significantly improving signal-to-noise ratio without broadening the spectral linewidth, and demonstrating quantum enhancement effects.

Contribution

It introduces the use of polarization squeezed states to improve SNS signal quality and maintains spectral resolution, a novel approach in atomic ensemble measurements.

Findings

PSS improves SNR compared to PCS.

SNR enhancement correlates with squeezing level.

Quantum control of SNS parameters achieved.

Abstract

We measured the spin noise spectroscopy (SNS) of rubidium atomic ensemble with two different atomic vapor cells (filled with the buffer gases or coated with paraffin film on the inner wall), and demonstrated the enhancement of signal to noise ratio (SNR) by using of the polarization squeezed state (PSS) of 795 nm light field with Stokes operator S2 squeezed. PSS is prepared by locking the relative phase between the squeezed vacuum state of light obtained by a sub-threshold optical parametric oscillator and the orthogonal polarized local oscillator beam by means of the quantum noise lock. Under the same conditions, PSS can be employed not only to improve SNR, but also to keep the full width at half maximum (FWHM) of SNS unchanged, compared with the case of using polarization coherent state (PCS), and the enhancement of SNR is positively correlated with the squeezing level of PSS. With the increase of probe laser power and atomic number density, the SNR and FWHM of SNS will increase correspondingly. With the help of PSS of Stokes operator S2, quantum enhancement of both SNR and FWHM of SNS signal has been demonstrated by controlling optical power of the S2 polarization squeezed light beam or atomic number density in our experiments.