arXiv subjects

A. V. Akimov

Publications and source records attributed to A. V. Akimov.

At least 19 recordsLinked to original sources

arXiv2026

Squeezing for dispersive readout of NV magnetometer

Nitrogen vacancy centers in diamond have established themselves as good sensing element for various type of sensors. In particular magnetometers based on diamond impurities are quickly developing and are already on the market. Yet, optical readout in these systems complicates system design. Recently schemes of dispersive readout of nitrogen vacancy spin state using high finesse dielectric cavities for microwave field were proposed, which do not use the optical readout scheme. However, only shot noise based estimates were so far done for sensitivity of these devices. Here we provide detailed analysis of various practically relevant noise and loss sources for such a system. Furthermore, we consider the possibility of using the squeezing quantum state of the probing microwave field and show it allows to improve the device performance even at room temperature.

quant-ph↗

arXiv2026

Speckle-based feedback control of optical dipole trap axial waist position

Cold neutral atoms is a powerful tool for many experiments ranging from frequency standards and sensing to quantum simulations. Sensitive experiments often demand transferring cold atoms from one vacuum chamber to the other with better optical access and vacuum. In case the transfer is done with a beam waist controlled by a focus-tunable lens, repeatability of the transfer as well as stability of the final position can be below the experimental demands. Here we implement the scheme for stabilization of the axial waist position of the optical dipole trap in the whole range of transfer (38 cm) using speckle patterns, which provides enough stability to achieve Bose-Einstein condensation of around 4*10^4 thulium atoms in the trap formed by the transport beam and the other beam in the target vacuum volume

quant-ph↗

arXiv2025

Dispersive readout with two orthogonal modes of a dielectric cavity

Nitrogen-vacancy color centers in diamond have proven themselves as a good, sensitive element for the measurement of magnetic fields. While the mainstream of magnetometers based on NV centers uses so-called optically detected magnetic resonance, there has recently been a suggestion to use dispersive readout of a dielectric cavity to enhance the sensitivity of magnetometers. Here, we demonstrate that the dispersive readout approach can be significantly improved if a two-channel scheme is considered.

quant-ph↗

arXiv2025

Factor of 1000 suppression of the depolarization rate in ultracold thulium collisions

Lanthanides are nowadays extensively used to investigate the properties of strongly correlated matter. Nevertheless, exploiting the Zeeman manifold of a lanthanide atom ground state is challenging due to the unavoidable presence of depolarization collisions. Here we demonstrate that in the case of the thulium atom, it is possible to suppress this depolarization by a factor of 1000 with a carefully tuned magnetic field thus opening the way for the efficient use of the Zeeman manifold in quantum simulations.

cond-mat.quant-gas↗

arXiv2025

Low frequency phase stabilization and phase tuning of an optical lattice with a variable period

Optical lattices play a significant role in the field of cold atom physics, particularly in quantum simulations. Varying the lattice period is often a useful feature, but it presents the challenge of maintaining lattice phase stability in both stationary and varying-period regimes. Here, we report the realization of a low frequency feedback loop for a tunable optical lattice. Our scheme employs a CCD camera, a computer, and a piezoelectric actuator mounted on a mirror. Using this setup, we significantly improved the long-term stability of an optical lattice over durations exceeding 10 seconds. More importantly, we demonstrated a rapid change in the optical lattice period without any loss of phase. The developed phase stabilization algorithm can be extended to more complicated 2D latices, than just periodic lattice.

cond-mat.quant-gas↗

arXiv2025

Double electron resonance with two ensembles of nitrogen-vacancy centers in diamond

Nitrogen-vacancy (NV) centers in diamond are widely used in the development of a number of sensors. The sensitivity of these devices is limited by both the number of centers used and their coherent properties. While the effects on the coherent properties of paramagnetic impurities such as carbon 13-isotopes and p1 centers are rather well understood, the mutual interaction of NV centers, which becomes especially important in relatively dense NV ensembles, is less well understood. Here, we provide a systematic study of NV-NV interaction using a dynamical double electron-electron resonance sequence, making it possible to directly observe the interaction of NV centers. Two types of dynamical DEER sequences were considered, consisting of 3 and 4 pulses. The nature of the phase jump in the 3-pulse sequence was attributed to the effect of non-commuting rotations within the sequence. Both the phase of the state vector rotation and its amplitude decay were studied, thus presenting a complete picture of decoherence due to NV-NV interaction. It was shown that the rate of the state vector decay differed significantly from predictions for a spin 1/2 system. However, the decay rate observed in the DEER sequence remained a reliable indicator of the concentration of bath spins and could be used to measure NV center concentration, provided that the magnetic transition of NV centers is saturated.

quant-ph↗

arXiv2025

Bichromatic microwave manipulation of the NV center nuclear spin using transition not detectable via optically detected magnetic resonance

Recently, rotation sensors utilizing the nuclear spins of nitrogen-vacancy color centers in diamond have been demonstrated. However, these devices are power-intensive and challenging to integrate into small chip-based radiofrequency antennas and circuits necessary for controlling nuclear spins or producing relatively high magnetic fields. To address this issue, the coherent manipulation of nuclear spins via coherent population trapping at moderate magnetic fields using microwave fields has been successfully demonstrated in isotopically pure diamond. In this work, we demonstrate that a similar technique can be applied to a diamond plate with a natural abundance of carbon-13, which holds significant potential for practical sensing applications. Although the forbidden resonances required for coherent control were only partially observed, coherent population trapping was successfully demonstrated at both visible and invisible transitions, with an apparent contrast of up to 98+-11% and a true contrast of approximately 35+-7%. This finding confirms the feasibility of coherent nuclear spin control even in diamond plates with naturally occurring carbon-13

quant-ph↗

arXiv2024

Optimization of the sensitivity of a temperature sensor based on germanium-vacancy color center (GeV) in diamond

Temperature sensors based on the GeV color center in diamond are gaining considerable attention in both scientific and industrial fields. For widespread industrial adoption, however, these sensors need a design that is as simple and cost-effective as possible. The original sensor design relied on measuring the spectral characteristics of the zero-phonon line. Recently, a modified approach was introduced, which involves splitting the GeV emission with a dichroic mirror and determining temperature based on the ratio of the two resulting signals. In this analysis, we provide a detailed comparison of both methods. At room temperature, the two methods show comparable performance, with slight variations depending on component quality. However, at temperatures around 300 °C, the new method's performance is estimated to be nearly twice that of the original, provided optimal filter parameters are used. Additionally, the sensitivity of the new method remains roughly consistent with its performance at room temperature.

physics.ins-det↗

arXiv2024

Inspiration from machine learning on example of optimization of the Bose-Einstein condensate of thulium atoms in a 1064-nm trap

The number of atoms in Bose-Einstein condensate determines the scale of experiments that can be performed, making it crucial for quantum simulations. Optimization of the number of atoms in the condensate is a complex problem which could be efficiently solved using machine learning technique. Nevertheless, this approach usually does not give any insight in the underlying physics. Here we demonstrate possibility to learn physics from the machine learning on an example of condensation of thulium atoms at a 1064-nm dipole trap. Optimization of the number of condensed atoms revealed a saturation, which was explained as limitation imposed by a 3-body recombination process. This limitation was successfully overcome by leveraging Fano-Feshbach resonances.

quant-ph↗

arXiv2023

Interaction of Nitrogen-Vacancy Centers in Diamond with a Dense Ensemble of Carbon-13

The nitrogen-vacancy center in diamond attracts a lot of attention in sensing applications, mainly for temperature, magnetic field, and rotation measurements. Nuclear spins of carbon-13 surrounding the nitrogen-vacancy center can be used as a memory or sensing element. In the current work, a diamond plate with a relatively large concentration of carbon-13 was synthesized and examined. The spectrum of optically detected magnetic resonance was recorded and analyzed in a magnetic field range of 5-200 G. A strain-independent measurement technique of carbon-13 isotope concentration based on the analysis of magnetic resonance spectra was developed. Additionally, narrow features in the spectrum were detected and understood.

quant-ph↗

arXiv2023

Bose-Einstein condensate as a diagnostic tool for an optical lattice formed by 1064 nm laser light

Recently, the thulium atom has been cooled down to the temperature of Bose-Einstein condensation. While the condensate of the thulium atom has a lot of applications in quantum simulations and other areas of physics, it can also serve as a unique diagnostic tool for many atomic experiments. In the present study, the Bose-Einstein condensate of the thulium atom was successfully utilized to diagnose an optical lattice and detect unwanted reflections in the experiments with the 1064 nm optical lattice, which will further be used in a quantum gas microscope experiment.

physics.atom-ph↗

arXiv2023

Losses of thulium atoms from optical dipole traps operating at 532 and 1064 nm

Recently thulium has been condensed to Bose-Einstein condensate. Machine learning was used to avoid a detailed study of all obstacles making cooling difficult. This paper analyses the atomic loss mechanism for the 532 nm optical trap, used in the Bose-condensation experiment, and compares it with the alternative and more traditional micron-range optical dipole trap. We also measured the scalar and tensor polarizability of thulium at 1064 nm and was found to be $167\pm 25$ a.u. ($275\pm 41\times {{10}^{-41}}\text{F }\cdot \text{ }{\text{m}^{\text{2}}}$) and $-4\pm 1$ a.u. ($7\pm 2\times {{10}^{-41}}\text{F }\cdot \text{ }{\text{m}^{\text{2}}}$).

physics.atom-ph↗

arXiv2022

Optimal microwave control pulse for nuclear spin polarization and readout in dense nitrogen-vacancy ensembles in diamond

Nitrogen-vacancy centers possessing nuclear spins are promising candidates for a novel nuclear spin gyroscope. Preparation of a nuclear spin state is a crucial step to implement a sensor that utilizes a nuclear spin. In a low magnetic field, such a preparation utilizes population transfer, from polarized electronic spin to nuclear spin, using microwave pulses. The use of the narrowband microwave pulse proposed earlier is inefficient when magnetic transitions are not well resolved, particularly when applied to diamond with a natural abundance of carbon atoms or dense ensembles of nitrogen-vacancy centers. In this study, the authors performed optimization of the pulse shape for 3 relatively easily accessible pulse shapes. The optimization was done for a range of magnetic transition linewidths, corresponding to the practically important range of nitrogen concentrations (5-50 ppm). It was found that, while at low nitrogen concentrations, optimized pulse added very little to simple square shape pulse, and in the case of dense nitrogen-vacancy ensembles, with a rather wide magnetic transition width of 1.5 MHz optimal pulses, a factor of 15% improvement in the population of the target state was observed.

quant-ph↗

arXiv2022

The study of the efficiency of nitrogen to NV-center conversion in high nitrogen content samples

The nitrogen-vacancy color center in diamond is one of the most important systems in the fast-growing field of sensing. This color centers are used in both high-resolution and high-sensitivity sensors. However, techniques for quick and efficient formations of this color center are still in the development stage. In this paper, we present a study on the influence of the electron irradiation dose on the conversion of substitutional nitrogen into $\text{N}{\text{V}^{-}}$ centers. The study was done on diamonds that were highly enriched with nitrogen (~100 ppm), which on one hand should maximize the effect of irradiation, and on another be of interest for high-sensitivity magnetometers. The maximum achieved conversion efficiency was as high as ${37\pm 3.7}$, with no observed saturation on the electron dose even with the simplest annealing procedure. The measurements of the corresponding dephasing time made it possible to estimate for shot-noise limited sensitivity per unit volume of a stationary field sensor with such a diamond to be ${9\pm 1\times {{10}^{-14}}\text{T}}/{\sqrt{\text{Hz}\cdot \text{m}{\text{m}^{-3}}}}\;$.

cond-mat.mtrl-sci↗

arXiv2022

The Phase-I Trigger Readout Electronics Upgrade of the ATLAS Liquid Argon Calorimeters

The Phase-I trigger readout electronics upgrade of the ATLAS Liquid Argon calorimeters enhances the physics reach of the experiment during the upcoming operation at increasing Large Hadron Collider luminosities. The new system, installed during the second Large Hadron Collider Long Shutdown, increases the trigger readout granularity by up to a factor of ten as well as its precision and range. Consequently, the background rejection at trigger level is improved through enhanced filtering algorithms utilizing the additional information for topological discrimination of electromagnetic and hadronic shower shapes. This paper presents the final designs of the new electronic elements, their custom electronic devices, the procedures used to validate their proper functioning, and the performance achieved during the commissioning of this system.

physics.ins-det↗

arXiv2021

Characterizing the temperature dependence of Fano-Feshbach resonances of Ultracold Polarized Thulium

Recent studies demonstrated anomalous temperature shifts for some Fano-Feshbach resonances of thulium atoms. These anomalies were explained by the variation in light intensity in the optical dipole trap, which accompanied changes in temperature. In addition, a temperature-related transformation of the statistics of the interresonance spacing was demonstrated [1]. Here, we analyze the shifts of isolated s- and d-type Fano-Feshbach resonances of ultracold thulium atoms with temperature for a fixed depth of an optical dipole trap. The measurements are consistent with the 3-body recombination-based theory of the temperature-related resonance shift and enable the extraction of the resonance parameters, particularly the magnetic moments of closed channel states. This parameter and the known polarizability of the open channel enable us to separate the contributions of the temperature and Stark shift to the overall shift of the resonances and show the dominant role of the Stark effect in the overall shift.

physics.atom-ph↗

arXiv2020

Random matrix theory analysis of a temperature-related transformation in statistics of Fano-Feshbach resonances in Thulium atoms

Recently, transformation from random to chaotic behavior in the statistics of Fano-Feshbach resonances was observed in thulium atoms with rising ensemble temperature. We performed random matrix theory simulations of such spectra and analyzed the resulting statistics. Our simulations show that, when evaluated in terms of the Brody parameter, resonance statistics do not change or change insignificantly with rising temperature if temperature is the only changing parameter. In the experiments evaluated, temperature was changed simultaneously with optical dipole trap depth. Thus, simulations included the Stark shift based on the known polarizability of the free atoms and assuming their polarizability remains the same in the bound state. Somewhat surprisingly, we found that, while including the Stark shift does lead to minor statistical changes, it does not change the resonance statistics and, therefore, is not responsible for the experimentally observed statistic transformation. This observation suggests that either our assumption regarding the polarizability of Feshbach molecules is poor or that an additional mechanism changes the statistics and leads to more chaotic statistical behavior.

physics.atom-ph↗

arXiv2020

Microwave coherent spectroscopy of ultracold thulium atoms

Recently, the thulium atom was cooled down to the Bose-Einstein condensation temperature, thus opening a pathway to quantum simulation with this atom. However, successful simulations require instruments to control and readout states of the atom as well as the ability to control the interaction between either different species or different states of the same type of species. In this paper, we provide an experimental demonstration of high-fidelity (over 93%) manipulation of the ground state magnetic sublevels of thulium, which utilizes a simple and efficient design of a microwave (MW) antenna. The coherence time and dephasing rate of the energetically highest hyperfine level of the ground state were also examined.

physics.atom-ph↗