Measurements of spin properties of atomic systems in and out of equilibrium via noise spectroscopy

Abstract

We explore the applications of spin noise spectroscopy (SNS) for detection of the spin properties of atomic ensembles in and out of equilibrium. In SNS, a linearly polarized far-detuned probe beam on passing through an ensemble of atomic spins acquires the information of the spin correlations of the system which is extracted using its time-resolved Faraday-rotation noise. We measure various atomic, magnetic and sub-atomic properties as well as perform precision magnetometry using SNS in rubidium atomic vapor in thermal equilibrium. Thereafter, we manipulate the relative spin populations between different ground state hyperfine levels of rubidium by controlled optical pumping which drives the system out of equilibrium. We then apply SNS to probe such spin imbalance nonperturbatively. We further use this driven atomic vapor to demonstrate that SNS can have better resolution than typical absorption spectroscopy in detecting spectral lines in the presence of various spectral broadening mechanisms. I. INTRODUCTIONControl of spin population and its simultaneous nondestructive detection play a crucial role in diverse scientific fields such as atom interferometry [1], precision mag- netometry [2], atomic clocks [3], quantum simulation [4]and quantum information processing [5]. While external magnetic fields and optical pumping can be used to manipulate the spin polarization and population in an atomic system, spin noise spectroscopy (SNS) [6-8] provides a means of the detection of such spin coherences * mswar@rri.res.in † srishic@rri.res.in ‡ sanjukta@rri.res.in mal agitation of the electrons in an electrical conductor [9], the intensity fluctuations in the emission of random lasers [10,11] and the stochastic fluctuations in clonal cellular constituents [12,13].The optical SNS technique has been developed by Aleksandrov and Zapasskii [14] to passively probe intrinsic spin fluctuations or magnetization noise in a thermal ensemble of spins. These spin ensembles can be made of electron spins in atomic systems and spins of electrons or holes in semiconductors and other solid-state materials.A study of SNS in alkali atomic vapor of Rb and potassium (K) in thermodynamic equilibrium was carried out by [15], which indicated that the electronic and nuclear gfactors, isotope abundance ratios, nuclear moments and hyperfine splittings could be measured. The first successful application of SNS to a solid-state system was performed by [16], for measuring the electron's Lande gfactor and spin relaxation time in a n-doped GaAs semiconductor. There has been significant progress in the recent years to extend the applicability of SNS [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32].First, we perform the SNS of Rb atoms in thermal equilibrium. We demonstrate accurate measurements of several physical quantities such as electron's g-factor, nuclear g-factor, isotope abundance ratios, and develop precision magnetometry with our thermal Rb vapor in the presence of a static magnetic field perpendicular to probe laser. While prio...

Raman scattering model of the spin noise

“…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].…”

Observation of optical Rabi oscillations in transmission signal of atomic vapor under continuous-wave laser excitation

“…Different behavior of optical spin noise spectra in Rb vapor for homogeneous and inhomogeneous broadenings was demonstrated in [16]. Applications of spin noise spectroscopy for studies of magnetic resonances, linear optics, and Raman scattering were addressed in [17][18][19]. The same technique was used in [20] for measurement of transverse spin-relaxation rates in a rubidium vapor.…”

Detection of Spin Coherence in Cold Atoms via Faraday Rotation Fluctuations

“…In the absence of finite magnetization along the light propagation direction, the dynamical magnetic properties of the sample can be found from the temporal fluctuations of dispersive Faraday rotation. Such Faraday rotation noises have been extensively studied within the spin noise spectroscopy (SNS) [14][15][16] technique to detect the intrinsic spin dynamics in atomic vapors [17][18][19][20], semiconductor heterostructures [21], quantum dots [22,23], spin-exchange collisions [24,25] and exciton-polaritons [26,27]. The SNS is also applied for precision magnetometry by using a spectral resolution of the spin noise signals from thermal atomic vapors [17,18] or semiconductors [28].…”

“…The measured P (ω)| Ω=0 is presented in Fig. 2(a), which shows the Lorentzian FWHM of ∼ 150 kHz for 87 Rb atoms in thermal equilibrium at T = 388 K. The details of the instrumentation used can be found in [18,39].…”