Transient dynamics of nonlinear magneto-optical rotation in the presence of transverse magnetic field

Nonlinear magneto-optical rotation is studied under non-equilibrium conditions. The polarization rotation of linearly polarized light traversing a rubidium vapor cell is observed versus the time-dependent (swept) longitudinal magnetic field in the presence of static transverse magnetic fields. Presence of the transverse fields modifies the character of the observed signals. In particular, for weaker transverse fields, field sweep leads two-harmonic oscillation of the polarization rotation while crossing zero. Unlike the steady-state, it was found that two-frequency oscillations observed in the transient signals, are independent of the transverse-field direction. For stronger transverse fields, the oscillations deteriorate eventually reaching a situation when no-oscillating dynamic signal, with distinct minimum close to zero field, is observed. Experimental results are supported with theoretical analysis based on the density-matrix formalism. The analysis confirms all the features of experimental results while providing an provide intuitive explanation of the observed behavior based on angular-momentum probability surfaces used for density-matrix visualization

Different sensitivities of two optical magnetometers realized in the same experimental arrangement

In this article, operation of optical magnetometers detecting static (DC) and oscillating (AC) magnetic fields is studied and comparison of the devices is performed. To facilitate the comparison, the analysis is carried out in the same experimental setup, exploiting nonlinear magneto-optical rotation. In such a system, a control over static-field magnitude or oscillating-field frequency provides detection of strength of the DC or AC fields. Polarization rotation is investigated for various light intensities and AC-field amplitudes, which allows to determine optimum sensitivity to both fields. With the results, we demonstrate that under optimal conditions the AC magnetometer is about ten times more sensitive than its DC counterpart, which originates from different response of the atoms to the fields. Bandwidth of the magnetometers is also analyzed, revealing its different dependence on the light power. Particularly, we demonstrate that bandwidth of the AC magnetometer can be significantly increased without strong deterioration of the magnetometer sensitivity. This behavior, combined with the ability to tune the resonance frequency of the AC magnetometer, provide means for ultra-sensitive measurements of the AC field in a broad but spectrally-limited range, where detrimental role of static-field instability is significantly reduced.Comment: 9 pages, 6 figure

Nonlinear Faraday effect and its applications

This chapter provides introduction to the important method of contemporarymagneto-optics, the nonlinear Faraday effect. It starts with a theoretical backgroundlinking the nonlinearity of the effect with quantum coherences of atomic states. Thediscussion of methods enabling analytical and numerical calculation of nonlinearmagneto-optical rotation are given. Next, Essential aspects of a typical experimen-tal apparatus used for investigation of the effect are described. Finally, the most im-portant applications of the phenomenon are reviewed, such as in magnetometry, nu-clear magnetic resonance, magnetic resonance imaging, magnetic particle detectionand quantum-state engineering

Limitations of rotating-wave approximation in magnetic resonance : characterization and elimination of the Bloch–Siegert shift in magneto-optics

We present investigations of radio-frequency (RF) resonances observed in an optically pumped rubidium vapor. By measuring the systematic shifts (the Bloch–Siegert shifts) of RF resonances in low magnetic fields, we demonstrate limitations of the rotating-wave approximation in the case of angular momentum $F \geq 1$. The resonance shifts and deformations are characterized in a wide range of parameters and it is shown that the observed behavior is far more complex than in a standard two-level system. It is also demonstrated that the shifts can be controllably turned on or off by switching between the oscillating and rotating magnetic field. Experimental results are supported with numerical calculations, reproducing all features of the observed signals. Besides fundamental aspect of the research, application of rotating magnetic field helps to suppress/evaluate spectroscopic-measurement and precise-metrology systematic errors. The reported study has also important implications for quantum metrology and information processing beyond RWA and standard two-state qubit dynamics

Tailoring population transfer between two hyperfine ground states of 87^{87}Rb

In this paper, we investigate the coherent control over a complex multilevel atomic system using the stimulated Raman adiabatic passage. Based on the example of $^{87}$Rb atoms, excited with circularly polarized light at the D$_{1}$ line, we demonstrate the ability to decompose the system into three- and four-level subsystems independently interacting with light beams. Focusing on the four-level system, we demonstrate that the presence of an additional excited state significantly affects the dynamics of the system evolution. Specifically, it is shown that, through the appropriate tuning of the light beams, some of the transfer channels can be blocked, which leads to better control over the system. We also demonstrate that this effect is most significant in media free from inhomogeneous broadening (e.g., Doppler effect) and deteriorates if such broadening is present. For instance, the motion of atoms affects both the efficiency and selectivity of the transfer

Light shift averaging in paraffin-coated alkali vapor cells

Light shifts are an important source of noise and systematics in optically pumped magnetometers. We demonstrate that the long spin coherence time in paraffin-coated cells leads to spatial averaging of the light shifts over the entire cell volume. This renders the averaged light shift independent, under certain approximations, of the light-intensity distribution within the sensor cell. These results and the underlying mechanism can be extended to other spatially varying phenomena in anti-relaxation-coated cells with long coherence times.Comment: 6 pages, 4 figure

Zero-field NMR J-spectroscopy of organophosphorus compounds

Organophosphorus compounds are a wide and diverse class of chemicals playing a crucial role in living organisms. This aspect has been often investigated using nuclear magnetic resonance (NMR), which provides information about molecular structure and function. In this paper, we report the results of theoretical and experimental studies on basic organophosphorus compounds using zero-field NMR, where spin dynamics are investigated in the absence of a magnetic field with the dominant heteronuclear J-coupling. We demonstrate that the zero-field NMR enables distinguishing the chemicals owing to their unique electronic environment even though their spin systems have the same alphabetic designation. Such information can be obtained just in a single measurement, while amplitudes and widths of observed low-field NMR resonances enable the study of processes affecting spin dynamics. An excellent agreement between simulations and measurements of the spectra, particularly in the largest frequency J-couplings range ever reported in zero-field NMR, is demonstrated

13^{13}C and 15^{15}N benchtop NMR detection of metabolites via relayed hyperpolarization

Parahydrogen-based nuclear spin hyperpolarization allows various magnetic-resonance applications, and it is particularly attractive because of its technical simplicity, low cost, and ability to quickly (in seconds) produce large volumes of hyperpolarized material. Although many parahydrogen-based techniques have emerged, some of them remain unexplored due to the lack of careful optimization studies. In this work, we investigate and optimize a novel parahydrogen-induced polarization (PHIP) technique that relies on proton exchange referred to below as PHIP-relay. An INEPT (insensitive nuclei enhanced by polarization transfer) sequence is employed to transfer polarization from hyperpolarized protons to heteronuclei ($^{15}$N and $^{13}$C) and nuclear signals are detected using benchtop NMR spectrometers (1 T and 1.4 T, respectively). We demonstrate the applicability of the PHIP-relay technique for hyperpolarization of a wide range of biochemicals by examining such key metabolites as urea, ammonium, glucose, amino acid glycine, and a drug precursor benzamide. By optimizing chemical and NMR parameters of the PHIP-relay, we achieve a 17,100-fold enhancement of $^{15}$N signal of [$^{13}$C, $^{15}$N$_{2}$]-urea compared to the thermal signal measured at 1 T. We also show that repeated measurements with shorter exposure to parahydrogen provide a higher effective signal-to-noise ratio compared to longer parahydrogen bubbling

Multi-Channel Data Acquisition System with Absolute Time Synchronization

A low-cost, stand-alone Global-Positioning-System-time-synchronized data acquisition system is described. The constructed prototype allows recoding up to four analog signals with a 16-bit resolution in variable ranges and a maximum sampling rate of 1000 S/s. Additionally, two digital readouts of external sensors can be acquired. A complete data set is stored on a Secure Digital (SD) card or transmitted to a computer using Universal Serial Bus (USB). The estimated time accuracy of the data acquisition is better than 0.2 {\mu}s. The device is envisioned for the use in a global distributed sensor network (the Global Network of Optical Magnetometers for Exotic physics - GNOME), whose aim is to search for new particles and interactions