arXiv subjects

A. Sokolov

Publications and source records attributed to A. Sokolov.

At least 19 recordsLinked to original sources

arXiv2026

Persistence of Entangled States and High Fidelity Quantum Gate Operations in Si/SiGe Spin Qubits at High Temperature

We characterize single- and two-qubit operations in a SiGe quantum dot array, from the perspective of its quantum information processing capabilities. The analysis includes rigorous randomized benchmarking of single- and two-qubit gates, SPAM characterization, and Bell's state tomography, which are all basic functionality required for universal quantum computation. To assess compatibility with integrated cryogenic electronics, we evaluate qubit performance at 350 mK, 500 mK, and 750 mK, with high fidelity single and two qubit operations. The highest temperature, 750 mK, falls within the realistic thermal budget for practical integrated cryogenic electronics and represents the highest operating temperature reported for this qubit platform.

quant-ph↗

arXiv2025

QSHS: An Axion Dark Matter Resonant Search Apparatus

We describe a resonant cavity search apparatus for axion dark matter constructed by the Quantum Sensors for the Hidden Sector (QSHS) collaboration. The apparatus is configured to search for QCD axion dark matter, though also has the capability to detect axion-like particles (ALPs), dark photons, and some other forms of wave-like dark matter. Initially, a tuneable cylindrical oxygen-free copper cavity is read out using a low noise microwave amplifier feeding a heterodyne receiver. The cavity is housed in a dilution refrigerator and threaded by a solenoidal magnetic field, nominally 8T. The apparatus also houses a magnetic field shield for housing superconducting electronics, and several other fixed-frequency resonators for use in testing and commissioning various prototype quantum electronic devices sensitive at a range of axion masses in the range 2.0 to 40 micro-eV/c2. The apparatus as currently configured is intended as a test stand for electronics over the relatively wide frequency band attainable with the TM010 cavity mode used for axion searches. We present performance data for the resonator, dilution refrigerator, and magnet, and plans for the first science run.

physics.ins-det↗

arXiv2024

Observation of $Ω(2012)^- \to Ξ(1530)\bar{K}$ and measurement of the effective couplings of $Ω(2012)^-$ to $Ξ(1530)\bar{K}$ and $Ξ\bar{K}$

Using $Υ(1S)$, $Υ(2S)$, and $Υ(3S)$ data collected by the Belle detector, we discover a new three-body decay, $Ω(2012)^-\toΞ(1530)\bar K\toΞπ\bar K$, with a significance of 5.2~$σ$. The mass of the $Ω(2012)^-$ is $(2012.5\pm0.7\pm0.5)$ MeV and its effective couplings to $Ξ(1530)\bar{K}$ and $Ξ\bar{K}$ are $(39^{+31}_{-39}\pm9)\times10^{-2}$ and $(1.7\pm0.3\pm0.3)\times10^{-2}$, where the first uncertainties are statistical and the second are systematic. The ratio of the branching fraction for the three-body decay to that for the two-body decay to $Ξ\bar{K}$ is $0.99\pm0.26\pm0.06$, assuming isospin symmetry.

hep-ex↗

arXiv2024

Commercial CMOS Process for Quantum Computing: Quantum Dots and Charge Sensing in a 22 nm Fully Depleted Silicon-on-Insulator Process

Confining electrons or holes in quantum dots formed in the channel of industry-standard fully depleted silicon-on-insulator CMOS structures is a promising approach to scalable qubit architectures. In this communication, we present measurement results of a commercial nanostructure fabricated using the GlobalFoundries 22FDX(TM) industrial process. We demonstrate here that quantum dots are formed in the device channel by applying a combination of a back- and gate voltages. We report our results on an effective detuning of the energy levels in the quantum dots by varying the barrier gate voltages in combination with the back-gate voltage. Given the need and importance of scaling to larger numbers of qubits, we demonstrate here the feasibility of single-electron box sensors at the edge of the quantum dot array for effective charge sensing in different operation modes -- sensing charge transitions in a single- and double quantum dots forming the quantum dot array. We also report measurement results demonstrating bias triangle pair formation and precise control over coupled quantum dots with variations in the inter-dot barrier. The reported measurement results demonstrate the ability to control the formation and coupling of multiple quantum dots in a quantum dot array and to sense their charge state via a Single Electron Box sensor in a commercial process for the first time.

cond-mat.mes-hall↗

arXiv2024

Recent results on the low-pressure GEM-based TPC at an Accelerator Mass Spectrometer

The Accelerator Mass Spectrometry technique makes it possible to measure rare long-lived isotopes such as $^{10}$Be, $^{14}$C, $^{26}$Al, $^{36}$Cl, $^{41}$Ca and $^{129}$I. The content of these isotopes can be at the level of 10$^{-15}$ of the total element content. The Accelerator Mass Spectrometer developed by Budker Institute of Nuclear Physics (BINP AMS) successfully measures the concentration of $^{14}$C relative $^{12}$C. However, there is a problem of separating the $^{10}$B isobaric background from $^{10}$Be. Beryllium-10 is used to date geological objects on a time scale from 1 thousand years to 10 million years. To solve this problem we have proposed a new technique for ion identification based on measuring both ion track ranges and ion energies in a low-pressure Time-Projection Chamber (TPC) with Gas Electron Multiplier (GEM) readout. We have developed the TPC with a dedicated thin silicon nitride window for an efficient passage of ions. To begin with, the characteristic of the low-pressure TPC were studied in isobutane at a pressure of 50 torr using alpha particle sources. In this work, we set up the low-pressure TPC on BINP AMS facility and successfully measured track ranges and energies of ions from samples containing $^{14}$C. At the next stage, we are going to carry out measurements with samples containing $^{10}$Be. However, using the obtained results and SRIM simulation we have already shown that the isobaric boron and beryllium ions can be separated by more than 5 sigma. This technique is proposed to be applied in AMS for dating geological objects, namely for geochronology of Cenozoic era.

physics.ins-det↗

arXiv2023

First observation of neutral bremsstrahlung electroluminescence in liquid argon

A recent discovery of additional mechanism of electroluminescence (EL) in noble gases due to the neutral bremsstrahlung (NBrS) effect led to a prediction that NBrS EL should be present in noble liquids as well. A theoretical model of NBrS EL in noble liquids was developed accordingly in the frameworks of Cohen-Lekner and Atrazhev. In this work, we confirm this prediction: for the first time, visible-range EL has been observed in liquid argon at electric fields reaching 90~kV/cm, using Gas Electron Multiplier (GEM) and Thick GEM (THGEM) structures. Absolute light yields of the EL were measured and found to be in excellent agreement with the theory, provided that the momentum-transfer cross section of electron scattering is used for calculation of NBrS cross section (instead of the energy-transfer one).

physics.ins-det↗

arXiv2023

Possible evidence for the production of Ar$_2^{*-}$ metastable negative molecular ions in gaseous argon of two-phase detectors for dark matter searches

Our recent studies of electroluminescence (EL) properties in two-phase argon detectors for dark matter searches have revealed the presence of unusual delayed pulses in the EL signal in the form of two slow components with time constants of about 5 and 50 $μ$s. These components were shown to be present in the charge signal itself, which clearly indicates that drifting electrons are temporarily trapped on two states of metastable negative argon ions which have never been observed before. In this work, using the pressure dependence of the ratio of slow component contributions measured in experiment, it is deduced that these states are those of two types of metastable negative molecular ions, $\mathrm{Ar}_2^{*-}(b \ ^4Σ_u^-)$ and $\mathrm{Ar}_2^{*-}(a \ ^4Σ_g^+)$ for the higher and lower energy level respectively.

physics.ins-det↗

arXiv2023

Unraveling the puzzle of slow components in gaseous argon of two-phase detectors for dark matter searches using Thick Gas Electron Multiplier

The effect of proportional electroluminescence (EL) is used to record the primary ionization signal (S2) in the gas phase of two-phase argon detectors for dark matter particle (WIMP) searches and low-energy neutrino experiments. Our previous studies of EL time properties revealed the presence of two unusual slow components in S2 signal of two-phase argon detector, with time constants of about 4-5 $μ$s and 50 $μ$s. The puzzle of slow components is that their time constants and contributions to the overall signal increase with electric field (starting from a certain threshold), which cannot be explained by any of the known mechanisms of photon and electron emission in two-phase media. There are indications that these slow components result from delayed electrons, temporarily trapped during their drift in the EL gap on metastable negative argon ions of yet unknown nature. In this work, this hypothesis is confirmed by studying the time properties of electroluminescence in a Thick Gas Electron Multiplier (THGEM) coupled to the EL gap of two-phase argon detector. In particular, an unusual slow component in EL signal, similar to that observed in the EL gap, was observed in THGEM itself. In addition, with the help of THGEM operated in electron multiplication mode, the slow component was observed directly in the charge signal, confirming the effect of trapped electrons in S2 signal. These results will help to unravel the puzzle of slow components in two-phase argon detectors and thus to understand the background in low-mass WIMP searches.

physics.ins-det↗

arXiv2023

New technique of ion identification in Accelerator Mass Spectrometry using low-pressure TPC with GEM readout

We have developed and successfully tested a low-pressure Time Projection Chamber (TPC) with Gas Electron Multiplier (GEM) readout for Accelerator Mass Spectrometry (AMS). AMS facility in Novosibirsk has a problem of separating isobar ions of different chemical elements that have the same atomic mass. The typical example is radioactive isotopes 10Be and 10B that are used to date geological objects at a time scale of ten million years. To solve this problem, a new ion identification technique, namely that based on measuring both ion track ranges and ion energies in low-pressure TPCs with GEM readout, has been developed. This technique is proposed to be applied in AMS for dating geological objects, namely for geochronology of Cenozoic era. In this work, we developed a new larger version of the TPC with a dedicated thin silicon nitride window for an efficient passage of ions. The TPC characteristics were studied in isobutane at low pressures using alpha particle sources. In addition, the use of GEM instead of THGEM has been shown to substantially improve the energy resolution at a nominal pressure (50 torr). Using these results and SRIM code simulations, it is shown that isobaric boron and beryllium ions can be effectively separated at AMS, providing efficient dating on a scale of ten million years. This technique will be applied in the AMS facility in Novosibirsk in the near future.

physics.ins-det↗

arXiv2023

Primary Cosmic Rays Energy Spectrum and Mean Mass Composition by the Data of the TAIGA Astrophysical Complex

The corrected dependence of the mean depth of the EAS maximum $X_{max}$ on the energy was obtained from the data of the Tunka-133 array for 7 years and the TAIGA-HiSCORE array for 2 years. The parameter $\langle\ln A\rangle$, characterizing the mean mass compositon was derived from these results. The differential energy spectrum of primary cosmic rays in the energy range of $2\cdot 10^{14}$ - $2\cdot 10^{16}$\,eV was reconstructed using the new parameter $Q_{100}$ the Cherenkov light flux at the core distance 100 m.}

astro-ph.HE↗

arXiv2022

TAIGA -- an advanced hybrid detector complex for astroparticle physics and high energy gamma-ray astronomy

The physical motivations, present status, main results in study of cosmic rays and in the field of gamma-ray astronomy as well future plans of the TAIGA-1 (Tunka Advanced Instrument for cosmic ray physics and Gamma Astronomy) project are presented. The TAIGA observatory addresses ground-based gamma-ray astronomy and astroparticle physics at energies from a few TeV to several PeV, as well as cosmic ray physics from 100 TeV to several EeV. The pilot TAIGA-1 complex is located in the Tunka valley, ~50 km west from the southern tip of the lake Baikal.

astro-ph.IM↗

arXiv2022

Puzzling time properties of proportional electroluminescence in two-phase argon detectors for dark matter searches

Proportional electroluminescence (EL) in noble gases is a physical process routinely used in two-phase (liquid-gas) detectors for low-energy astroparticle-physics experiments. In this work, the time properties of visible-light EL in two-phase argon detectors have been systematically studied for the first time. In particular, two unusual slow components in the EL signal, with their contributions and time constants increasing with electric field, were observed. This puzzling property is not expected in any of the known mechanisms of photon and electron emission in two-phase media. Time constants of these components is about 4-5 $μ$s and 50 $μ$s. In addition, a specific threshold behavior of the slow components was revealed: they emerged at a threshold in reduced electric field of 4.8 $\pm$ 0.2 Td regardless of the gas phase density, which is about 1 Td above the onset of standard (excimer) EL. There is a conspicuous similarity between this threshold and reduced field threshold of EL in NIR occurring via higher atomic excited states Ar$^{*}(3p^{5}4p)$. An unexpected temperature dependence of slow components was also observed: their contribution decreased with temperature, practically disappearing at room temperature. We show that the puzzling properties of slow components can be explained in the framework of hypothesis that these are produced in the charge signal itself due to trapping of drifting electrons on metastable negative argon ions.

physics.ins-det↗

arXiv2022

The Tunka-Grande scintillation array: current results

The Tunka-Grande experiment is a scintillation array with about 0.5 sq.km sensitive area at Tunka Valley, Siberia, for measuring charged particles and muons in extensive air showers (EASs). Tunka-Grande is optimized for cosmic ray studies in the energy range 10 PeV to about 1 EeV, where exploring the composition is of fundamental importance for understanding the transition from galactic to extragalactic origin of cosmic rays. This paper attempts to provide a synopsis of the current results of the experiment. In particular, the reconstruction of the all-particle energy spectrum in the range of 10 PeV to 1 EeV based on experimental data from four observation seasons is presented.

astro-ph.IM↗

arXiv2022

Study of visible-light emission in pure and methane-doped liquid argon

In liquid argon TPCs for dark matter search and neutrino detection experiments, primary scintillation light is used as a prompt signal of particle scattering, being intensively produced in the vacuum ultraviolet (VUV) due to excimer emission mechanism. On the other hand, there were indications on the production of visible-light emission in liquid argon, albeit at a much lower intensity, the origin of which is still not clear. The closely related issue is visible-light emission in liquid argon doped with methane, the interest in which is due to the possible use in neutron veto detectors for those experiments. In this work we study in detail the properties of such light emission in pure liquid argon and its mixtures with methane. In particular, the absolute photon yield of visible-light emission in pure liquid argon was measured to be about 200 and 90 photon/MeV for X-rays and alpha particles respectively. In liquid argon doped with methane the photon yield dropped down significantly, by about an order of magnitude at a methane molar content varying from 0.01 to 1%, and then almost did not change when further increasing the methane content up to 10%.

physics.ins-det↗

arXiv2020

Observation of unusual slow components in electroluminescence signal of two-phase argon detector

Proportional electroluminescence (EL) in noble gases is used in two-phase detectors for dark matter search to record ionization signals in the gas phase induced by particle scattering in the liquid phase (S2 signals). In this work, the EL pulse-shapes in a two-phase argon detector have for the first time been studied systematically in a wide range of reduced electric field, varying from 3 to 9 Td. The pulse-shapes were studied at different readout configurations and spectral ranges: using cryogenic PMTs and SiPMs, with and without a wavelength shifter (WLS), in the VUV and visible range. We observed the fast component and two unusual slow components, with time constants of about 5 $μ$s and 40 $μ$s. The unusual characteristic property of slow components was that their contribution and time constants increased with electric field.

physics.ins-det↗

arXiv2020

Observation of primary scintillations in the visible range in liquid argon doped with methane

Neutron veto detector based on liquid scintillator containing hydrogen atoms is an integral part of any underground experiment for dark matter search. So far, a flammable mixture of liquid hydrocarbons was used as a liquid scintillator in such detectors. A safe alternative might be a liquid scintillator based on liquid argon doped with methane. In this work, we have studied the primary scintillations in pure liquid argon and its mixtures with methane, the CH4 content varying from 100 ppm to 5%. The primary scintillations have for the first time been observed in liquid argon doped with methane, in the visible and near infrared range, and their relative light yields have been measured as a function of the CH4 content.

physics.ins-det↗

arXiv2019

Ion detector for Accelerator Mass Spectrometry based on low-pressure TPC with THGEM readout

A new technique for ion identification in Accelerator Mass Spectrometry (AMS) has been proposed by measuring the ion track ranges using a low-pressure TPC. As a proof of principle, a low-pressure TPC with charge readout using a THGEM multiplier was developed. The tracks of alpha particles from various radioactive sources were successfully recorded in the TPC. The track ranges were measured with a high accuracy, reaching the 2% resolution level. Using these results and the SRIM code simulation, it is shown that the isobaric boron and beryllium ions can be effectively separated at ten sigma level. It is expected that this technique will be applied in the AMS facility in Novosibirsk for dating geological objects, in particular for the geochronology of Cenozoic Era.

physics.ins-det↗

arXiv2019

Quest for detection of a cosmological signal from neutral hydrogen with a digital radio array developed for air-shower measurements

Digital radio arrays are widely used for the low-frequency radio astronomy as well as for detection of air-showers induced by high-energy cosmic rays and neutrinos. Since the radio emission from air-showers forms short broadband pulses with duration of tens nanoseconds, the data acquisition strategies of cosmic-ray and astronomical arrays have significant differences. To perform precise measurement of cosmic rays, the radio array should have absolute amplitude calibration and record the entire electric field on the antenna in the broad frequency range. These requirements are similar to ones defined for the experiments aimed at the detection of weak signal from neutral hydrogen at redshifts of $z$>10, what led us to the application of our experience with Tunka-Rex to this problem. We are developing new experimental setup comprising of four antenna stations, placed on the area of 100 sq.m. Each antenna station consists of two perpendicular loop antennas measuring electric field in the frequency band of 30-80 MHz. The setup records electric fields from all antennas in portions of 50 $μ$s reaching the spectral resolution of 20 kHz. We expect a flow of redundant data of about 10 GB/day, and plan to exploit this redundancy in order to decrease systematic uncertainty of the measurements by application of digital beam-forming, matched filtering and RFI suppression with neural networks. In the present contribution we describe the design and calibration of the setup, expected performance and data analysis techniques.

astro-ph.IM↗