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

Abstract

We measured the spin noise spectroscopy (SNS) of rubidium atomic ensemble with two different kinds of atomic vapor cells (filled with buffer gas or coated with paraffin film on the inner wall) and demonstrated the enhancement of the signal-to-noise ratio (SNR) by using polarization squeezed state (PSS) of 795-nm light field with Stokes operator S Λ 2 squeezed. The PSS is prepared by locking the relative phase between the squeezed vacuum state of light obtained with a sub-threshold optical parametric oscillator and the orthogonally polarized local oscillator beam by means of the quantum noise lock. Under the same conditions, the PSS can be employed not only to improve the SNR, but also to keep the full width at half maximum (FWHM) of SNS, compared with the case of using the polarization coherent state (PCS), enhancement of SNR is positively correlated with the squeezing level of the PSS. With increasing probe laser power and atomic number density, the SNR and FWHM of SNS will increase correspondingly. With the help of the PSS of the Stokes operator S Λ 2 , quantum improvements of both the SNR and FWHM of SNS signal has been demonstrated by controlling optical power of polarization squeezed light beam or atomic number density in our experiments.

Creation and dynamics of spin fluctuations in a noisy magnetic field

“…The results are shown in figure 7: the blue dots are the simulation results and the orange dashed line is a power-law fit function y(x) = ax k . While the standard, motion-induced spin noise signal in atomic vapors is well known to increase quadratically with the probe power P [12,38,39], the simulated variance of the spin noise induced by the magnetic noise scales like P 4 . This is perfectly consistent with an explanation in terms of residual absorption by the medium, leading to a small optical pumping: indeed, the probe laser then contributes both to the creation and to the detection of the spin noise.…”

Direct Measurement of Higher-Order Nonlinear Polarization Squeezing

“…Because of this importance, squeezed states of light are studied on various physical platforms [1][2][3][4][5], harnessing their nonclassical properties to advance the performance of quantum imaging, sensing, and information processing applications [6][7][8][9][10][11]. Among the different ways squeezing can manifest itself, spin and polarization squeezed states of light are of particular interest [12][13][14][15].…”