Measurement of Magnetic Field Constants by a Modified Method of Optical Orientation of Atoms

Evgenii B. Aleksandrov, A. M. Bonch-Bruevich, V. A. Khodovoǐ

O. S. Vasiutinskii, N. A. Dovator, R. A. Zhitnikov

Brian Julsgaard, Jacob Friis Sherson, Jens Lykke Sørensen +1 more

Quantum information protocols utilizing atomic ensembles require preparation of a coherent spin state (CSS) of the ensemble as an important starting point. We investigate the magneto-optical resonance method for characterizing a spin state of caesium atoms in a paraffin coated vapour cell. Atoms in a constant magnetic field are subject to an off-resonant laser beam and an RF magnetic field. The spectrum of the Zeeman sub-levels, in particular the weak quadratic Zeeman effect, enables us to measure the spin orientation, the number of atoms, and the transverse spin coherence time. Notably the use of 894 nm pumping light on the D1 line, ensuring the state F = 4, m F = 4 is a dark state, helps us to achieve spin orientation of better than 98%. Hence we can establish a CSS with high accuracy, which is critical for the analysis of the entangled states of atoms.

Evgenii B. Aleksandrov, O. V. Konstantinov, V. I. Perel

Ettore Majorana

L. N. Novikov, G. V. Skrotskiǐ, G. I. Solomakho

The history of the discovery, study, and explanation of the effect discovered fifty years ago by the German physicist Hanle and its development and generalization by the French school of physicists led by Kastler are described. The effect is observed optically in an increase in the degree of depolarization of the resonance fluorescence. It is studied in the range of magnetic fields in which the Zeeman splitting of the atomic magnetic sublevels does not exceed the level widths determined by thermal relaxation mechanisms and electromagnetic interaction. It is a direct optical manifestation of interference of degenerate atomic states and is intimately connected with the conservation law for the angular momentum of the photon-atom system. In the review, different applications of the effect to the measurement of mean lifetimes, linewidths, and Stark splitting constants of atoms in excited states are given. The resonance scattering of light by atoms in the ground state in a weak magnetic field is considered in detail—in particular, in the presence of radio-frequency magnetic fields oriented in different ways. The different possible types of parametric resonances in one or two radio-frequency fields for arbitrary orientation of the constant magnetic field are interpreted as the effect of crossing of the levels of an atom that is dressed by the radio-frequency field. Applications of the effect in the quantum magnetometry of ultraweak fields (down to 10-10 Oe) are examined.