Spin-alignment noise in atomic vapor

Abstract

In the conventional spin noise spectroscopy, the probe laser light monitors fluctuations of the spin orientation of a paramagnet revealed as fluctuations of its gyrotropy, i.e., circular birefringence. For spins larger than 1/2, there exists spin arrangement of a higher order-the so-called spin alignment-which also exhibits spontaneous fluctuations. We show theoretically and experimentally that alignment fluctuations manifest themselves as the noise of the linear birefringence. In a magnetic field, the spin-alignment fluctuations, in contrast to those of spin orientation, show up as the noise of the probe-beam ellipticity at the double Larmor frequency, with the most efficient geometry of its observation being the Faraday configuration with the light propagating along the magnetic field. We have detected the spin-alignment noise in a cesium-vapor cell probed at the wavelength of D2 line (852.3 nm). The magnetic-field and polarization dependence of the ellipticity noise are in full agreement with the developed theory.

Raman scattering model of the spin noise

“…Since 9) for the complex polarimetric signal 𝛿𝑢 that the components of this signal at the frequency 2𝜔 𝐿 behave as ∼ sin 2𝜃 and vanish when the probe beam polarization is parallel or perpendicular to the magnetic field (𝜃 = 0, 𝜋/2), as it has been observed in experiment [30].…”

“…In this section, we analyze spectral peculiarities of the noise signal and their dependence on the angle between the direction of the probe beam polarization plane and magnetic field. In the fourth section, we analyze, in the framework of the developed model, the mechanism of formation of the recently discovered ellipticity noise signal at double Larmor frequency (alignment noise) and compare our results with the experimental data obtained in [30]. The main results of the paper are summarised in Conclusions.…”

“…The quantum-mechanical correlation functions of the operators entering Eq. ( 15) were calculated in [30].…”

“…and low-dimensional media (e. g. [16,17]) can be addressed by SNS, but also the nuclear dynamics [18][19][20], light-matter interaction effects [21,22], spatial properties distribution [23,24], and even noise of valley redistribution of electrons [25]. Still the atomic systems attract the significant attention of researchers [26][27][28][29][30][31][32][33] as model objects which allow to reveal the fundamental pecularities of spin noise formation mechanics. In typical SNS experiments with polarimetric detection of the signal, one measures, in fact, the magnetization-noise power spectrum of the studied sample associated, in accordance with the fluctuation-dissipation theorem, with the spectrum of its magnetic susceptibility [34].…”

Spin noise correlations in multispecies hot atomic vapors

“…Deeper understanding of spin noise and its relation to the collisional relaxation processes [85][86][87] paves the way towards improving quantum enhanced metrology in hot vapor systems [88][89][90][91]. Some of the modern applications of spin noise spectroscopy in hot vapors are: measurement of zero-field spin noise using magnetic pulses [92], measurement of higher order spin noise like alignment noise [93,94], spin noise measurements with time-dependent magnetic fields [95,96], demonstration of quantum random number generator using spin noise [97], effects of atomic diffusion on the spin noise spectrum [98,99] and dual-species spin noise measurements [100][101][102][103][104]. Of particular interest in this thesis is the study of the noise properties in multispecies atomic systems.…”