Hyperfine-encoded qubits in alkali atoms have established themselves as robust platforms for quantum computing, while alkaline-earth-like elements expand the state manipulation toolbox through their rich spectrum of optical transitions and metastable states. In this work, we demonstrate that thulium is a viable candidate for quantum computing, combining advantages of hyperfine qubit encoding with a rich energy-level structure of alkaline-earth-like atoms. We describe protocols for the initial state preparation and state-selective readout, and show single-qubit operations on the microwave transition at 1497 MHz. We demonstrate ground-state hyperfine qubit coherence times up to T_{2}^{∗}=22_{−2}^{+2} s and T_{2}=55_{−14}^{+59} s, representing record-scale performance for neutral-atom systems. Furthermore, we show operations involving metastable optical states, including shelving for the state-selective readout as well as coherent population transfer of the ground-state qubit with coherence time primarily limited by the metastable level natural lifetime of 112 ms. These results mark the first step toward using thulium for quantum computing applications and highlight its promising characteristics.

We report on building a pulsed source of cold Tm atoms and loading of the narrow-line magneto-optical trap (MOT) from the cold atomic beam. We achieve the loading rate of the first-stage MOT in the primary chamber up to 108 atoms/s and obtain a cold atomic beam with the mean longitudinal velocity ∼10 m/s and an angular spread of 18 mrad in a pulsed mode. In this regime, we can form a cold atomic beam with up to 5 × 106 atoms at a 5 Hz repetition rate. We also introduce a novel method to enhance the capture velocity of the narrow-line MOT by incorporating an additional axial cooling beam and achieve loading efficiency η = 10% of the second-stage MOT in the science chamber. Our approach could be extended to other atomic species with similar properties, such as Sr, Yb, Dy, and Er, serving as a convenient alternative for the traditional 2D-MOT schemes. Providing rapid loading of the MOT in the science chamber, it would reduce preparation time of the atomic ensemble leading to a shorter dead time in spectroscopy experiments and a higher repetition rate.

Clock transition at $1.14 \mu \mathrm{m}$ in neutral thulium is a promising candidate for compact and robust transportable optical clock due to its extremely low sensitivity to external electric and magnetic fields. Cold Tm atoms are now used in optical lattice clocks, quantum simulators and for the study of Bose-Einstein condensation and cold collision physics. In this work, we discuss experimentally measured absolute frequencies of the two transitions at 410.6 nm and 530.7 nm, used for laser cooling of thulium atoms, transition at 418.8 nm used for optical pumping and clock transition at 1140 nm. Using accurate laser spectroscopy in an ensemble of cold thulium atoms, we measured frequencies of these transitions using an optical frequency comb, which was referenced to an active hydrogen maser. Transition frequencies were measured with an uncertainty at one tenth of their natural linewidth, which is sufficient for cooling and pumping of thulium atoms. The uncertainty of the clock transition frequency is 30 Hz, which was limited by the maser frequency calibration with GNSS. Our results can find application in existing experiments with cold thulium atoms and especially in new projects.

The experimental comparison of two thulium optical lattice clocks in a time interval of up to one hour has been carried out. The synchronous comparison of a clock transition in two independent atomic ensembles using a single ultrastable laser has allowed us to eliminate fluctuations of the laser frequency from the measured frequency difference and to reach a relative measurement error of 10–16 after 500-s averaging, which corresponds to a relative instability of $$2 \times {{10}^{{ - 15}}}{\text{/}}\sqrt \tau $$. The successful demonstration of the long-term operation of two systems using the synchronous comparison of clock transitions opens the possibility of studying systematic shifts in thulium optical clocks with an uncertainty of 10–17.

In this paper, we demonstrate the interaction of 674 nm laser radiation with a clock quadrupole transition in high-energy 88Sr+ ions obtained by laser ablation. The results of the spectrometry of the clock and the pump transitions are presented. We describe the parameters of the experimental setup and the protocol of the clock transition spectroscopy and analyze various line broadening mechanisms.

The hyperfine structure of atoms and ions is widely used in fundamental and applied research. Accurate knowledge of hyperfine splitting values is essential for quantum metrology applications as well as for improving the performance of systems designed for quantum computing and simulation. We present refined values of the hyperfine splitting frequencies of the ground and clock states of thulium atom, f_g^HFS=1 496 550 658.23(3) Hz and f_c^HFS=2 113 946 873.08(9) Hz, respectively. The measurements are performed on an ultracold atomic ensemble in an optical lattice using combined microwave and optical transition spectroscopy. Our results improve the accuracy by 2 and 7 orders of magnitude for f_g^HFS and f_c^HFS, respectively, compared to the previously published values. We also refine the value of the Landé g-factor of the clock level to g_c = 0.85479(11).

In the paper, we describe a method for searching for the optimal parameters of laser cooling of strontium ions without observing the luminescence signal. The presented method made it possible to obtain a cold cloud of ions, detect the luminescence signal, and achieve the mode of ionic crystals.

In this paper, we discuss the effect of destabilization of dark states in 88 Sr 1+ ions in an external magnetic field, provides theoretical calculations to describe the effect, describes the systems of magnetic field generation and changes in the polarization of laser radiation, and analyzes the experiment and the obtained dependences.

The article gives the results of generalization of a short-time expedition hydrological–hydrochemical survey in an arctic river basin in the northeastern part of Chaunskaya Lowland in the northern Chukotka, carried out in July 2020. At a scale of a small Yanranaivaam River basin, the structure of water masses was analyzed, and the catchments of individual tributaries with intense development of cryogenic processes were identified; these processes have an effect on water chemistry, in particular, in a higher concentration of hydrocarbonate ions, dissolved ferrum, and dissolved organic carbon. Two-tracer mixing model was used to identify and evaluate the contributions of water sources and their spatial relationships at the moment of survey. The main river water sources are atmospheric waters (mostly snowmelt water), slope soil water of the seasonally thawed layer (STL), and melt water of bald-mountain ice. The dominating water source in the catchments of the middle and upper parts of the basin is atmospheric water (67–78%), and that in the catchments of the lower part of the basin is STL soil water (59–64%). River recharge by meltwater of bald-mountain ice is typical of the entire basin, and at the moment of survey it accounted for 10–14% of the total.

Optical atomic clock based on 1.14 mu m transition in neutral thulium is considered as one of the promis-ing candidates for compact and robust transportable system owing to its very low sensitivity to external electric and magnetic fields. Besides optical clocks, cold Tm atoms are used in Bose-Einstein condensa-tion studies, cold collision physics and quantum simulators. In this work, we report measurements of the absolute frequencies of the two cooling transitions at 410.6 nm and 530.7 nm, and the optical pump-ing transition at 418.8 nm. Using accurate laser spectroscopy of these transitions in an ensemble of cold thulium atoms, we measured corresponding frequencies using a hydrogen maser-referenced optical fre-quency comb. Transition frequencies were determined with an uncertainty of about one tenth of the cor-responding natural linewidth which is good enough for straightforward cooling and pumping of atoms. Our results are useful for existing experiments with cold thulium atoms and even more demanded for new projects.(c) 2023 Elsevier Ltd. All rights reserved.

We propose a design of a source of cold thulium atoms based on a 2D magneto-optical trap and perform numerical simulation of its operation. Optimal parameters of cooling radiation and the magnetic field are determined; it is shown that for a total radiation power of 50 mW and an atomic oven temperature of 800 K, the proposed configuration can provide a flux of 4 × 10 8 cold atoms per second, and with an increase of the oven temperature, the flux can reach ~ 10 11 atom/s. Such a source can be used for building frequency standards as well as in experiments with quantum simulators and the Bose–Einstein condensate.

Synchronous comparison of optical clocks using phase-coherent clock lasers makes it possible to determine the difference (ratio) of clock transition frequencies, which is not limited by the total noise of lasers in use. A detailed simulation of the comparison of two thulium optical clocks is performed using synchronous interrogation of atoms by the radiation of a common clock laser. Some critical parameters have been determined, specifically: the residual noncorrelated frequency and amplitude noises of test pulses and reading noises, which may deteriorate the comparison stability. At the same time, it is demonstrated that this way is insensitive to fluctuations in the number of atoms, calibration of feedback-loop parameters, individual ejections in measurement cycles, and fluctuations of laboratory magnetic field.

The article analyses landscape factors that determine the runoff of small Arctic and Subarctic rivers in the far northeast of Asia. The paper considers hydrography, structure of permafrost landscapes and their hydro-chemical characteristics, and the spatial dynamics of low-water runoff in the basins of the Ugolnaya-Dionisiya and Yanranayvaam rivers. It has been established that sustainable water intake depends on the ratio of land-scapes generating and depositing the permafrost runoff, namely Arctic char gravelly shrub tundra, lowland tussock tundra and hummock swamps. The low-water runoff of 20-50 l/km2·sec is typical for the sources of rivers, where seasonal char ice melts in the slope deposits and condensation waters are formed. Melt water of sea-sonal intra-surface soil ice on the gentle slopes of tundra hummocks provides specific runoff of 10-20 l/km2·sec. Upland and lowland marshes deposit above-frozen waters, and their runoff is less than 10 l/km2ˑsec. Using the example of two catchment basins, it is shown that the decrease in precipitation in the north of Chukotka is almost completely compensated by the formation of condensation waters. At the same time, inground seasonal infiltration soil ice is replaced in Arctic landscapes by infiltration-condensation char ice, and its melt water makes up for the loss of surface runoff.

Deep laser cooling of atoms, ions, and molecules facilitates the study of fundamental physics as well as applied research. In this work, we report on the narrow-line laser cooling of thulium atoms at the wavelength of 506.2nm with the natural linewidth of 7.8kHz, which widens the limits of atomic cloud parameters control. Temperatures of about 400nK, phase-space density of up to 3.5×10−4 and 2×106 number of trapped atoms were achieved. We have also demonstrated formation of double cloud structure in an optical lattice by adjusting parameters of the 506.2nm magneto-optical trap. These results can be used to improve experiments with BEC, atomic interferometers, and optical clocks.

It is known that atmospheric pressure surges affect the discharge of underground water sources in large artesian basins. In southern latitudes, the groundwater tables change insignificantly following the diurnal variations of atmospheric pressure. There is no information on the influence of rapid changes in atmospheric pressure on the position of the surface of the suprapermafrost waters and river flow in the Arctic region. The study of the diurnal course of the level of underground suprapermafrost and surface waters was carried out to identify the links of river flow with atmospheric phenomena and cryogenic processes. It was found that the daily atmospheric pressure drop with an amplitude of 1.2 kPa in the area of the small Ugolnaya-Dionisia river, located in the Anadyr lowland in Chukotka, led to a simultaneous decrease and then an increase in the level of suprapermafrost underground and surface river basin waters by 2.5-7.8 cm. This corresponds to a short-term decrease and then an increase in the river water discharge by more than 3.5 times. To clarify the factors that determine the mechanism of the influence of atmospheric pressure on the water level and river flow, a consideration of the hydrophysical properties of aquifer-containing peat soils was carried out. Compression tests revealed that the elasticity of the peat soils horizon remains within the range of 0-15 kPa, which contributes to a dynamic change in porosity even with a slight change in the external load. This means that the atmospheric pressure changes during weather development are sufficient to modify the water capacity of peat soils and deposit them, and then discharge a part of the suprapermafrost flow. The discovered pressure impact in the tundra soils of the permafrost zone is a unique mechanism for providing plants with moisture during droughts and reducing the risk of tundra fires. As part of the further study of the pressure impact, it is planned to conduct laboratory experiments to determine the quantitative parameters of the change in the peat soils moisture capacity under pressure drops in the atmosphere. Mathematical modeling of the capillary moisture capacity of peat soils will be performed under conditions of ambient load changes. The results of experiments and theoretical studies are assumed to be useful for predicting the flow of bogged-up river basins, design of reclamation, and irrigation of areas of peat soils distribution.

This paper presents a detailed analysis of the effect of the optical lattice field on clock transition spectroscopy, as exemplified by thulium atoms. We consider the applicability of the sifting of atoms in an optical lattice by ramping down the power of the laser light that produces it. This method allows the number of filled vibrational sublevels to be reduced down to a single vibrational state, without changing the inner state of the atoms. The effectiveness of the method is illustrated by the example of the spectroscopy of a clock transition in thulium atoms in the resolved sideband regime.