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Vol 166, No 4 (2024)
METHOD FOR ESTIMATING THE NUMBER OF ATOMS IN MAGNETO-OPTICAL TRAPS
Abstract
A method for estimating the number of atoms in a magneto-optical trap and in the flux from a hot atom source is presented and examined in detail. The applicability of the method at various cooling stages is analyzed. The relative uncertainty of the method is calculated. The results of applying the described method on optical lattice clocks with cold strontium and ytterbium atoms are presented.
447-452
SOURCE OF ULTRACOLD ATOMS 87Rb FOR ATOMIC INTERFEROMETER-GRAVIMETER
Abstract
The results of experimental studies on creating a source of ultracold atoms 87Rb for an absolute quantum gravimeter based on atomic interference are presented. The studies resulted in sub-Doppler cooling of atoms 87Rb in a magneto-optical trap and in obtaining a cloud ~107 -108 of atoms with a temperature of 6 мкК. Using microwave radiation and optical pumping, the preparation of ultracold atoms in the initial state |F = 1, mF = 0〉is carried out and experiments are performed to observe Ramsey resonances at the transition |F = 1, mF = 0〉 → |F = 2, mF = 0〉during the interaction of the atomic cloud with unidirectional Raman radiation pulses.
453-459
COHERENCE EFFECTS OF MAGNETIC SUBLEVELS INDUCED BY A LINEARLY POLARIZED WAVE FIELD IN SATURATED ABSORPTION AND MAGNETIC SCANNING SPECTRA IN ATOMS WITH Λ- AND V-TYPE TRANSITIONS
Abstract
It has been shown analytically and numerically that the effect of magnetic coherence (interference) of levels in L- and V-type transitions, induced by the field of a traveling linearly polarized electromagnetic (EM) wave of arbitrary intensity, can make a significant contribution both to the populations of transition levels (more ~50% than of the field contribution) and to the absorption resonance spectra during frequency and magnetic scanning. Differences in the manifestation of the magnetic coherence effect in level populations for open and closed types of transitions have been identified. It has been established that narrow coherent electromagnetically induced transparency (EIT) resonances are formed in the absorption resonance spectra during magnetic scanning near zero magnetic field. The dependencies of EIT resonance parameters on the characteristics of atomic transitions and EM wave intensity have been investigated. The contribution of the magnetic coherence effect of transition levels to the shape of these resonances has been revealed.
460-474
METHODS AND SYSTEMS FOR COMPARING FREQUENCIES OF GEOGRAPHICALLY DISTANT OPTICAL STANDARDS
Abstract
Works for the future redefinition of the second based on quantum transition in the optical range are considered. The uncertainty budget of the Sr-1 optical frequency standard based on ultracold strontium atoms included in the State Primary Standard of Time and Frequency, is refined. Various methods for comparing frequencies of remote optical frequency standards are described to implement the "roadmap" adopted at the 27th General Conference on Weights and Measures. The accuracy characteristics maximally achievable when using the described methods are listed, and their comparison is given.
475-489
MICROWAVE RADIATION TRANSITIONS BETWEEN TRIPLET RYDBERG STATES OF ALKALINE-EARTH-LIKE ELEMENTS OF GROUP IIB IIB (Zn, Cd, Hg) AND YTTERBIUM Yb
Abstract
Numerical values of quantum defects us ed for calculations of frequencies and matrix elements of dipole radiation transitions in the microwave range between triplet Rydberg states n3S1, n3P1, n3D2 and n3F3 series of Group IIb atoms with large principal quantum numbers have been determined n > 20. The calculation results within semi-empirical methods of quantum defect theory and Fues model potential are approximated by quadratic polynomials. The polynomial coefficients are tabulated along with numerical values of frequencies and matrix elements and can be used for measuring field strengths through microwave-induced splitting of electromagnetically induced transparency resonance, for development and planning of studies of microwave radiation characteristics using Rydberg atoms.
490-499
500-503
504-516
TWO-TEMPERATURE DISTRIBUTION OF ATOMS UNDER SUB-DOPPLER COOLING CONDITIONS
Abstract
The problem of sub-Doppler laser cooling of atoms under "optical molasses" conditions in fields formed by counter-propagating waves with different polarization configurations is considered, with full accounting for quantum recoil effects. It is shown that the distribution of cold atoms is not in equilibrium but can nevertheless be approximated by two Gaussian functions and, accordingly, characterized by temperatures of "cold" and "hot" fractions. A detailed analysis of the atomic fractions and their temperatures depending on the parameters of light fields is carried out. Based on the obtained results, the concept of weighted average temperature can be introduced, which corresponds to the average kinetic energy of atoms.
517-526
OPTICAL STABILIZATION OF CHARGED DIELECTRIC NANOPARTICLES IN HYBRID TRAPS
Abstract
The results of a theoretical study of the dynamics of charged dielectric nanoparticles in a hybrid trap are presented. A new configuration of a hybrid trap is proposed, consisting of a surface electrodynamic trap with transparent electrodes and an optical dipole trap formed by a laser Gaussian beam. Dynamics simulation was carried out for silicon dioxide nanoparticles localized in a hybrid trap in an air environment, taking into account viscous friction. It is shown that the laser radiation intensity of the dipole trap can be used as a bifurcation parameter of the considered dynamical system to change the equilibrium position of nanoparticles. The proposed hybrid trap configuration can become a new platform for implementing an optomechanical Ising machine.
527-534
RABI OSCILLATIONS AT THREE-PHOTON LASER EXCITATION OF A SINGLE RUBIDIUM RYDBERG ATOM IN AN OPTICAL DIPOLE TRAP
Abstract
In an experiment on three-photon laser excitation 5S1/2 → 5P3/2 → 6S1/2 → 37P3/2 of a single 87Rb, Rydberg atom in an optical dipole trap, we have observed for the first time three-photon Rabi oscillations between the ground and the Rydberg states. A single atom was detected optically by resonance fluorescence signal using a low-noise sCMOS video camera. The relative probability for the atom to remain in the trap after the action of three synchronized exciting laser pulses with durations varying from 100 ns to 2 µs was measured. A distinctive feature of the experiment was the use of intense laser radiation with a wavelength of 1367 nm at the second excitation step, providing a single-photon Rabi frequency up to 2 GHz to control the effective detunings of intermediate levels of the three- photon transition due to the dynamic Stark effect. Rabi oscillations with frequencies from 1 to 5 MHz were registered depending on the intensity of laser pulses of the first and second excitation steps with coherence time 0.7–0.8 µs. Ways to increase the coherence time and contrast of three-photon Rabi oscillations for applications in quantum information with Rydberg atoms are discussed.
535-547
SUPPRESSION OF LIGHT SHIFT OF COHERENT POPULATION TRAPPING RESONANCES IN CESIUM VAPOR USING DOUBLE FREQUENCY AND AMPLITUDE MODULATION OF LASER RADIATION
Abstract
The light (ac Stark) shift of coherent population trapping (CPT) resonances in cesium vapor is studied under excitation by radiation from a vertical-cavity surface-emitting laser, whose current is modulated at a microwave frequency (≈ 4.6 GHz). This approach is used in some state-of-the-art microwave quantum frequency standards (QFS). One of the main factors leading to degradation of long-term frequency stability of QFS is associated with the light shift of the CPT resonance due to variations in optical power P in the vapor cell. In this work, it is shown that using an additional electro- optic modulator assembled as a Mach-Zehnder interferometer makes it possible to effectively control the amplitudes of sidebands in the radiation spectrum. This allows finding such an optimal optical power value near which the resonance shift is insensitive to its small changes. The results are of interest for the development of CPT-based QFS.
548-555
LASER COOLING OF YTTERBIUM-171 ION WITHOUT MAGNETIC FIELD
Abstract
A scheme for laser cooling of an 171Yb+ ion in a radio-frequency trap using a three-frequency laser field with its components resonant to optical transitions of the line 2 S1/ 2 → 2P1/ 2, which does not require a magnetic field, is experimentally implemented. The exclusion of the magnetic field in the laser cooling cycle allows for precise control of a weak magnetic field (∼ 10-2 Gs), used for spectroscopy of clock transitions in the optical frequency standard based on a single ytterbium ion, which is important for suppressing frequency shifts associated with the quadratic Zeeman effect.
556-565
DETECTION OF METRONIDAZOLE AND FAMPRIDINE BY NMR AT ZERO AND ULTRALOW MAGNETIC FIELD
Abstract
In this work the biocompatible molecules — metronidazole and fampridine — were successfully hyperpolarized using parahydrogen via the signal amplification by reversible exchange approach. The nuclear magnetic resonance (NMR) signals from both molecules were detected at zero- to ultralow magnetic field (ZULF) using commercially available rubidium vapor magnetometer from QuSpin.
566-570