Transition Frequency Research Articles

Fluorescence by incoherently pumped polar quantum dot placed in a low-frequency monochromatic field

Abstract We studied spectral properties of high-frequency fluorescent radiation from a two-level quantum system with broken inversion spatial symmetry, which can be implemented as a model of a one-electron two-level asymmetric polar semiconductor quantum dot whose electric dipole moment operator has permanent unequal diagonal matrix elements. The case of the excitation of this system by incoherent pumping of some sort supplemented with an additional driving monochromatic field, which frequency is much lower than the optical transition frequency of the quantum dot, was considered. An analytical expression for the fluorescence spectrum as a function of the amplitude and frequency of the monochromatic driving field, as well as of the pumping intensity, was derived. We also discussed feasible practical applications of the effects under study in the field of quantum optics and optoelectronics for the generation of high-frequency radiation, possessing stationary equidistant spectrum, and for the control of the radiative properties of such nanodevices as spasers (dipole nanolasers).

Approximate analytic solution of the dissipative semiclassical Rabi model under parametric multi-tone modulations

Abstract We present an analytic method for obtaining the dynamics of the dissipative time-modulated
semiclassical Rabi model, which describes a two-level system (qubit) with time-dependent parameters, 
coupled to a single-mode bosonic field via the dipole-interaction and to
a thermal reservoir. We consider the simultaneous harmonic
modulations of the qubit transition frequency and the qubit-field coupling strength,
with arbitrary frequencies, and obtain closed analytic expressions for the
density operator under the coarse-graining approximation. Our
approximate results are in excellent ageement with exact numerical data, and
illustrate how the qubit state can be controlled in the dispersive regime by properly
adjusting the system parameters.

TIBA: A web application for the visual analysis of temporal occurrences, interactions, and transitions of animal behavior.

Data in behavioral research is often quantified with event-logging software, generating large data sets containing detailed information about subjects, recipients, and the duration of behaviors. Exploring and analyzing such large data sets can be challenging without tools to visualize behavioral interactions between individuals or transitions between behavioral states, yet software that can adequately visualize complex behavioral data sets is rare. TIBA (The Interactive Behavior Analyzer) is a web application for behavioral data visualization, which provides a series of interactive visualizations, including the temporal occurrences of behavioral events, the number and direction of interactions between individuals, the behavioral transitions and their respective transitional frequencies, as well as the visual and algorithmic comparison of the latter across data sets. It can therefore be applied to visualize behavior across individuals, species, or contexts. Several filtering options (selection of behaviors and individuals) together with options to set node and edge properties (in the network drawings) allow for interactive customization of the output drawings, which can also be downloaded afterwards. TIBA accepts data outputs from popular logging software and is implemented in Python and JavaScript, with all current browsers supported. The web application and usage instructions are available at tiba.inf.uni-konstanz.de. The source code is publicly available on GitHub: github.com/LSI-UniKonstanz/tiba.

Solving the Puzzle of the Carbonic Acid Vibrational Spectrum - an Anharmonic Story.

Against the general belief that carbonic acid is too unstable for synthesis, it was possible to synthesize the solid[1,2] as well as gas-phase carbonic acid.[3] It was suggested that solid carbonic acid might exist in Earth's upper troposphere and in the harsh environments of other solar bodies,[4] where it undergoes a cycle of synthesis, decomposition, and dimerization.[5] To provide spectroscopic data for probing the existence of extraterrestrial carbonic acid,[2,6] matrix-isolation infrared (MI-IR) spectroscopy has shown to be essential.[3,4,6-8] However, early assignments within the harmonic approximation using scaling factors impeded a full interpretation of the rather complex MI-IR spectrum of H2CO3. Recently, carbonic acid was detected in the Galactic center molecular cloud,[9] triggering new interest in the anharmonic spectrum.[10] In this regard, we substantially reassign our argon MI-IR spectra based on accurate anharmonic calculations. We calculate a four-mode potential energy surface (PES) at the explicitly correlated coupled-cluster theory using up to triple-zeta basis sets, i. e., CCSD(T)-F12/cc-pVTZ-F12. On this PES, we perform vibrational self-consistent field and configuration interaction (VSCF/VCI) calculations to obtain accurate vibrational transition frequencies and resonance analysis of the fundamentals, first overtones, and combination bands. In total, 12 new bands can be assigned, extending the spectral data for carbonic acid and thus simplifying detection in more complex environments. Furthermore, we clarify disputed assignments between the cc- and ct-conformer.

Activities of Daily Living Disability Transition Patterns in Older Adults with Chronic Diseases: A Four-Year Cohort Study in China.

Older adults with chronic diseases often experience higher rates of Activities of Daily Living (ADL) disability, with research primarily examining the transition between states of ADL disability and non-disability. The current study aims to analyze the patterns and factors of mutual transitions between multiple different ADL disability states in older adults with chronic diseases. This longitudinal study utilized data from the Shanghai Elderly Care Unified Needs Assessment (SECUNA) spanning 2014 to 2017, with 2014 being the baseline. The study included older adults aged 60 years and older with chronic diseases. Using the Markov model, individuals were classified into three states: no ADL disability, mild ADL disability, and severe ADL disability. Transition patterns were analyzed by calculating the frequency, intensity, and probability of transition, and the influencing factors of six transition scenarios were evaluated. Older adults with mild ADL disability were more likely to experience improvement (transition intensity: 0.4731) rather than deterioration (transition intensity: 0.2226) in their ADL disability states. However, those with severe ADL disability faced challenges in improving their states (transition intensities: 0.0068 and 0.1204). Among the six ADL disability transition scenarios, place of residence was associated with four scenarios, age and economic sources were associated with three scenarios, sex was associated with two scenarios, and other factors were associated with one scenario. The transition patterns and factors differ among individuals with varying ADL disability states. It is essential for relevant agencies to implement tailored preventive healthcare strategies to effectively manage the health status of older adults with chronic diseases.

The ambivalent relationship of e-scooters and public transport: Evidence from France

This paper aims at assessing competitiveness of shared e-scooters relative to public transport proposing a methodology that uses empirical data at the individual trip level and comparing e-scooter trips with the alternative public transit route available to the traveler at the time of the trip, as estimated by a navigation and public transit application. This allows us to obtain information at the individual transit trip level, such as in-vehicle time, walking, waiting, and other. We then explore the competitiveness between the two alternatives using two performance measures – travel time (TT) and an estimation of the generalized cost (GC) of a trip – for different levels of aggregation. Results show that in general, e-scooters are more competitive in terms of travel time. However, due to the higher pricing, generalized cost of transit is generally lower than that of e-scooter. In 60% of the cases users would lower their generalized cost by using public transport instead of e-scooter. On average, e-scooter is a better option for trips up to 15min, while public transit is better for longer trips. They are also more competitive during hours when transit frequency is reduced, as well as in areas with reduced service. Finally, we also find that one in five trips complement public transport service offering transportation outside of transit service hours or between areas with no connectivity. Further research should include surveys in order to obtain more details on the psychological constructs of the users.

Observation of Discrete Charge States of a Coherent Two-Level System in a Superconducting Qubit.

We report observations of discrete charge states of a coherent two-level system (TLS) that is strongly coupled to an offset-charge-sensitive superconducting transmon qubit. We measure an offset charge of 0.072e associated with the two TLS eigenstates, which have a transition frequency of 2.9GHz and a relaxation time exceeding 3ms. Combining measurements in the strong dispersive and resonant regime, we quantify both transverse and longitudinal coupling of the TLS-qubit interaction. We further perform joint tracking of TLS transitions and quasiparticle tunneling dynamics but find no intrinsic correlations. This Letter demonstrates microwave-frequency TLS as a source of low-frequency charge noise.

Reducing inhomogeneous broadening of spin and optical transitions of nitrogen-vacancy centers in high-pressure, high-temperature diamond

With their optical addressability of individual spins and long coherence time, nitrogen-vacancy (NV) centers in diamond are often called “atom-like solid spin-defects”. As observed with trapped atomic ions, quantum interference mediated by indistinguishable photons was demonstrated between remote NV centers. In high sensitivity DC magnetometry at room temperature, NV ensembles are potentially rivaling with alkali-atom vapor cells. However, local strain induces center-to-center variation of both optical and spin transitions of NV centers. Therefore, advanced engineering of diamond growth toward crystalline perfection is demanded. Here, we report on the synthesis of high-quality HPHT (high-pressure, high-temperature) crystals, demonstrating a small inhomogeneous broadening of the spin transitions, of T2* = 1.28 μs, approaching the limit for crystals with natural 13C abundance, that we determine as T2* = 1.48 μs. The contribution from strain and local charges to the inhomogeneous broadening is lowered to ~17 kHz full width at half maximum for NV ensemble within a > 10 mm3 volume. Looking at optical transitions in low nitrogen crystals, we examine the variation of zero-phonon-line optical transition frequencies at low temperatures, showing a strain contribution below 2 GHz for a large fraction of single NV centers.

Caffeine Intake Alters Recovery Sleep after Sleep Deprivation.

Caffeine is a well-known psychostimulant reputed to alleviate the deleterious effects of sleep deprivation. Nevertheless, caffeine can alter sleep duration and quality, particularly during recovery sleep. We evaluated the effects of acute caffeine intake on the duration and quality of recovery sleep following total sleep deprivation (TSD), taking into account daily caffeine consumption. Forty-one participants performed a double-blind, crossover TSD protocol (38 h of continuous wakefulness) with acute caffeine or placebo. Caffeine (2.5 mg/kg) or placebo was administered twice during continuous wakefulness (last treatment 6.5 h before bedtime for the recovery night). Polysomnographic measurements were recorded using a connected headband. TSD was associated with a rebound in total sleep time (TST) on the recovery night (+110.2 ± 23.2 min, p < 0.001). Caffeine intake decreased this recovery TST (-30.2 ± 8.2 min p = 0.02) and the N3 sleep stage duration (-35.6 ± 23.2 min, p < 0.01). Caffeine intake altered recovery sleep continuity (increased number of long awakenings), stability (higher stage transition frequency), and organization (less time spent in complete sleep cycle) and decreased the delta power spectral density during NREM sleep. On the recovery night, habitual daily caffeine consumption was negatively correlated with TST in caffeine and placebo conditions and positively correlated with wake after sleep onset (WASO) duration and with the frequency of long (>2 min) awakenings in the caffeine condition only. Acute caffeine intake during TSD affects nighttime recovery sleep, with an interaction with daily consumption. These results may influence advice on caffeine intake for night-shift workers. (NCT03859882).

Grating pitch comparator traceable to the Cr atom transition frequency

Calibration of the grating pitch typically requires metrological instruments or diffraction techniques. The traceability and stability demands for laser wavelength in these techniques present substantial challenges for on-site grating calibration. This paper introduces a novel traceability approach to grating pitch calibration using a grating pitch comparator that utilizes the transition frequency of the chromium. The chromium transition frequency is converted into a chromium grating through atom lithography, establishing a self-traceable length standard dCr = 212.7787 ± 0.0049 nm. Calibration of the test grating’s pitch is achieved by comparing the phase shift caused by the simultaneous movement of the chromium grating and the test grating. By using the dCr, this approach combines the high-accuracy of fundamental physical constants with the environmental stability of grating interferometers, eliminating the need for measuring laser wavelength, air refraction, diffraction angles. It significantly enhances the precision and makes more straightforward and portable, crucial for facilitating traceable on-site grating measurements.

Turn on, Tune in, and Listen up: Maximizing Side-Channel Recovery in Cross-Platform Time-to-Digital Converters

Voltage fluctuation sensors measure minute changes in an FPGA power distribution network, allowing attackers to extract information from concurrently executing computations. Previous voltage fluctuation sensors make assumptions about the co-tenant computation and require the attacker have a priori access or system knowledge to tune the sensor parameters statically. Additionally, prior voltage fluctuation sensors make use of proprietary vendor intellectual property and do not provide guidance on sensor migration to other vendors. We present the open-source design of the Tunable Dual-Polarity Time-to-Digital Converter, which introduces three dynamically tunable parameters that optimize signal measurement, including the transition polarity, sample window, frequency, and phase. We show that a properly tuned sensor improves co-tenant classification accuracy by 2.5 \(\times\) over prior work and increases the ability to identify the co-tenant computation and its microarchitectural implementation. Across 13 varying applications, our techniques yield an 80% classification accuracy that generalizes beyond a single board. Our sensor improves the ability of a correlation power analysis attack to rank correct subkey values by 2 \(\times\) . As an extension to our prior work, we show that the voltage fluctuation sensor is portable to multiple FPGA vendors, and we demonstrate implementations on both Xilinx and Intel FPGA systems.

Geometry of the argon…imidazole complex revealed by the microwave spectra of four isotopologues

The rotational spectra of four isotopologues of an isolated complex formed between an argon atom and imidazole, Ar…imidazole, have been recorded in the 6–19 GHz region by Fourier transform microwave spectroscopy. Rotational transition frequencies have been fitted to Watson’s S-reduced Hamiltonian to yield rotational, centrifugal distortion and nuclear quadrupole coupling constants for the complex. Rotational constants determined for the parent and three 15N-containing isotopologues allow the three-dimensional structure of the complex to be described. The two angles, θ and ϕ, which define the orientation of the Ar atom relative to the imidazole ring have been determined for the first time in addition to the distance between Ar and the center of mass of the imidazole sub-unit, R. Fitting of structural parameters to the experimentally-determined moments of inertia yields a structure where Ar is positioned above the ring plane at a distance of 3.519 Å from the center of mass of the imidazole sub-unit. In the experimentally determined, average geometry, the intermolecular axis (drawn through Ar and the center of mass of the imidazole sub-unit) is oriented at 6° from the normal to the ring plane. The experimental results allow for four alternative possibilities for ϕ with 62.0(39)° being that which is most consistent with expectations for this parameter based on previous work. The experimentally-determined nuclear quadrupole coupling constants imply that the electric field gradient at each of the nitrogen nuclei of imidazole does not significantly change on formation of the complex with Ar.

Measurement of transition frequencies and hyperfine constants of molecular iodine at 520.2 nm

We measured the transition frequencies of the hyperfine components in the four lines (P(34) 39-0, R(36) 39-0, P(33) 39-0, and R(35) 39-0) of the B-X transitions of molecular iodine at 520.2 nm. The 520.2 nm laser was generated by wavelength-converting the output of a 1560.6 nm external-cavity diode laser using a dual-pitch periodically poled lithium niobate (PPLN) waveguide. The frequencies were measured by counting the heterodyne beats between the laser stabilized at the frequencies of the hyperfine components and a frequency comb synchronized with a hydrogen maser. We determined the transition frequencies of the a1 components with relative uncertainties of 1×10−11; the uncertainty was limited by the impurity of the molecular iodine in the cell. From the measured hyperfine splitting frequencies, we calculated the hyperfine constants of these four transitions to obtain the rotational dependence of the excited-state hyperfine constants.

Nocturnal Sleep Dynamics Alterations in the Early Stages of Behavioral Variant Frontotemporal Dementia.

Sleep disorders have been recognized as an integral component of the clinical syndrome in several neurodegenerative diseases, including Alzheimer's Disease (AD). However, limited data exists for rarer types of neurodegenerative diseases, such as behavioral variant Frontotemporal Dementia (bvFTD). This study aims to analyze EEG power spectra and sleep stage transitions in bvFTD patients, hypothesizing that bvFTD may show distinctive sleep stage transitions compared to patients with Alzheimer's Disease (AD). Eighteen probable bvFTD patients and eighteen age- and sex-matched probable AD patients underwent overnight polysomnography (PSG) and completed sleep disorders questionnaires. Sleep questionnaires, full-night EEG spectra, and sleep stage transitions indexes were compared between groups. bvFTD patients had higher Insomnia Severity Index (ISI) scores (95%CI: 0, 5) and reported poorer sleep quality than AD patients (p<0.01). Compared to AD, bvFTD patients showed higher N1 percentage (95%CI: 0.1, 6), lower N3 percentage (95%CI: -13.6, -0.6), higher sleep-wake transitions (95%CI: 1.49, 8.86) and N1 sleep-wake transitions (95%CI: 0.32, 6.1). EEG spectral analysis revealed higher spectral power in bvFTD compared to AD patients in faster rhythms, especially sigma rhythm, across all sleep stages. In bvFTD patients, sleep-wake transitions were positively associated with ISI. Patients with bvFTD present higher rates of transitions between wake and sleep than AD patients. The increased frequency of sleep transitions indicates a higher degree of sleep instability in bvFTD, which may reflect an imbalance in sleep-wake promoting systems. Sleep stage transitions analysis may provide novel insights into the sleep alterations of bvFTD patients.

Constraints on the variation of physical constants, equivalence principle violation, and a fifth force from atomic experiments

The aim of this paper is to derive limits on various forms of “new physics” using atomic experimental data. Interactions with dark energy and dark matter fields can lead to space-time variations of fundamental constants, which can be detected through atomic spectroscopy. In this study, we examine the effects of a varying nuclear mass mN and nuclear radius rN on two transition ratios: the comparison of the two-photon transition in atomic hydrogen with the hyperfine transition in Cs133 based clocks, and the ratio of optical clock frequencies in Al+ and Hg+. The sensitivity of these frequency ratios to changes in mN and rN enables us to derive new limits on the variations of the proton mass, quark mass, and the QCD parameter θ. Additionally, we consider the scalar field generated by the Yukawa-type interaction of feebly interacting hypothetical scalar particles with Standard Model particles in the presence of massive bodies such as the Sun and Moon. Using the data from the Al+/Hg+, Yb+/Cs, and Yb+(E2)/Yb+(E3) transition frequency ratios, we place constraints on the interaction of the scalar field with photons, nucleons, and electrons for a range of scalar particle masses. We also investigate limits on the Einstein equivalence principle (EEP) violating term (c00) in the Standard Model extension (SME) Lagrangian and the dependence of fundamental constants on gravity. Published by the American Physical Society 2024

Graph-let based approach to evolutionary behaviors in chaotic time series

In the Graph-let based time series analysis, a time series is mapped into a series of graph-lets, representing the local states respectively. The bridges between successive graph-lets are reduced simply to a linkage with an information of occurrence. In the present work, we focus our attention on the bridge series, i.e., preserve the structures of the bridges and reduce the states into nodes. The bridge series can tell us how the system evolves. Technically, the ordinal partition algorithm is adopted to construct the graph-lets and the bridges. Results for the Logistic Map, the Hénon Map, and the Lorenz System show that the statistical properties for transition frequency network for the bridges, e.g., the number of visited bridges and the average out-entropy-degree, have the capability of characterizing chaotic processes, being equivalent with the Lyapunov exponent. What is more, the topological structure can display the details of the contributions of the transitions between the bridges to the statistical properties.

A wide angle beam scanning CRLH leaky-wave antenna with non-identical elements per unit-cells

In this research article, a wide-angle scanning leaky-wave antenna (LWA) based on the composite right/left-handed (CRLH) metamaterial (MTM) operating over the C-band spectrum for mobile applications is proposed, investigated, and realized. The proposed LWA includes nine CRLH-MTM-based unit-cells. The properties of CRLH-MTM have been applied using series slots and shunt metallic via-holes. Each unit cell consists of three patches, two external patches, and one smaller middle patch implemented between them. One slot has been etched on each external patch; the width of these two slots is unequal. Moreover, the distance of the middle patch with each side patch is different. The results show that using this method of realizing non-identical elements caused the achievement of proper return-loss at the transition frequency and provided the balanced CRLH metamaterial condition. Additionally, using CRLH-MTM properties by realizing series capacitance (slot) and shunt inductance (via-holes) made the wide-angle scant from backward to forward radiation pattern. The results demonstrate that the LW antenna with small dimensions of 251.5 × 30 × 1.575 mm3 operates over a frequency range of 4.8–6.13 GHz covering a wide beam scanning range from −63° to +65° with broadside radiation at the center frequency of 5.46 GHz. The radiation gain of the proposed antenna varies from 6.2–13.1 dB. The achievements confirm the effectiveness of the proposed methods to realize a high-performance LW-antenna with the advantages of simple design, low profile, low cost, and easy of manufacture for mobile applications.

CPT and Lorentz symmetry tests with hydrogen using a novel in-beam hyperfine spectroscopy method applicable to antihydrogen experiments

We present a Rabi-type measurement of two ground-state hydrogen hyperfine transitions performed in two opposite external magnetic field directions. This puts first constraints at the level of ▪ on a set of coefficients of the Standard Model Extension, which were not measured by previous experiments. Moreover, we introduce a novel method, applicable to antihydrogen hyperfine spectroscopy in a beam, that determines the zero-field hyperfine transition frequency from the two transitions measured at the same magnetic field. Our value, ▪, is in agreement with literature at a relative precision of 0.44 ppb. This is the highest precision achieved on hydrogen in a beam, improving over previous results by a factor of 6.

Shortened and simplified traceability chain for dimensional metrology based on self-traceable standards

Abstract Nanoscale measurement is an essential task of nanomanufacturing, and measurement traceability is a fundamental aspect of nanoscale measurement. High-precision nanoscale measurement instruments (e.g. atomic force microscopes (AFM) and scanning electron microscopes (SEM)) need to be calibrated by traceable standards to ensure their accuracy and reliability. However, due to the suboptimal accuracy, uniformity, and consistency of existing standards, they need to be calibrated by metrological instruments traceable to primary length standards (e.g. physical wavelength standards) before use. This results in a long traceability chain that leads to error accumulation and significantly reduces calibration efficiency. This paper proposes a novel shortened and simplified traceability chain, where the physical wavelength standard corresponding to the 7S3 → 7P4° transition frequency of chromium atoms is materialized into self-traceable gratings using the atom lithography technology. The self-traceable gratings can then be directly applied for calibrating measurement instruments. To verify this approach, the self-traceable gratings are calibrated using a metrological AFM of the Physikalisch-Technische Bundesanstalt. Measurement results confirmed the feasibility of the approach. Particularly, our results show that the self-traceable gratings have excellent uniformity over different measurement areas and consistency over different samples, both at 0.001 nm level. Finally, the application of the self-traceable gratings for the calibrations of a commercial AFM and SEM is demonstrated. The new traceability chain significantly simplifies the calibration process, providing a more reliable and higher efficient calibration approach for advanced nanomanufacturing than that of the state-of-the-art.

Energy level spectrum and lattice polarization of polaron in metal halide perovskite parabolic quantum wells

In this study, polaron effect in 2D metal halide perovskite materials (TMHPMs), which naturally form quantum well (QW) structures, has been investigated. Polarization of carriers and lattice within these structures was explored based on unitary transformation and variational methods. Specifically, lattice polarization and energy level transition spectra of strong coupling polaron in parabolic potential metal halide perovskite QWs (MAPbCl3, MAPbBr3, and MAPbI3) were studied. Also, we calculated ground and first excited state energies, excitation energy, transition frequency, and vibration frequency of a TMHPM QWs. Our results indicated that parabolic potential confinement intensity affected related physical quantities, which provided insight to investigate metal halide perovskite materials and polaron effect.