We've developed a scalable and sustainable online atomic data portal with an automated interface for easy update and addition of new data. The current portal provides energies, transition matrix elements, transition rates, radiative lifetimes, branching ratios, polarizabilities, hyperfine constants, and other data, for 28 atoms and ions. It also features an interactive polarizability plotting interface for neutral atoms and singly-charged ions. The data production is supported by recent developments of open-access atomic software based on our research codes, including new workflow algorithms, which allow large volumes of such data to be generated with automated accuracy assessments. This entails a new method of comparing our calculated values with data from the NIST Atomic Spectra Database. All calculated values include estimated uncertainties. Data for more systems will be added in the future. Experimental values are included with references, where high-precision data are available.

Ever since the proposal of delayed choice quantum erasure and subsequent realization in the experiment by Kim et al., the interpretation and implications of delayed-choice experiments have remained a subject of intense foundational debate. This paper resolves the apparent paradox attached to the experiment using standard quantum mechanics. Using an extended Mach-Zehnder interferometer which captures every operational feature of the original experiment, we show that choosing between which-path and erasure detectors is simply a choice of measurement bases, which does not rewrite a photon's past. Furthermore, by mapping the experiment to a two-way Stern-Gerlach framework, we prove that quantum erasure is an expected result of measuring entangled states, not a physical anomaly. Ultimately, through a pedagogical game, we illustrate that the illusion of retrocausality arises from asking illegitimate questions, and that a forward-in-time description is entirely sufficient to explain the logic.

In this work, the $4D_{3/2}|3,\pm2\rangle \rightarrow 4D_{5/2}|3,\pm2\rangle$ transition in the Nb$^{4+}$ ion is identified as a promising candidate for a terahertz (THz) atomic clock, with the transition frequency occurring at 56.0224 THz. This transition is primarily driven by the magnetic dipole decay channel, which can easily be accessed by a laser. We focus on the stable $^{93}$Nb isotope, which has 100\% natural abundance and a nuclear spin of $I=9/2$ for experimental advantage. Our data analysis allows us to estimate potential systematic shifts in the proposed clock system, including those due to blackbody radiation, electric quadrupole, second-order Zeeman, and second-order Doppler {shifts}. {The scheme presented in this study can help suppress the AC Stark and electric quadrupole shifts in the clock frequency measurement.} {All these analyses} suggest that the proposed THz atomic clock using Nb$^{4+}$ could be valuable in both quantum thermometry and frequency metrology.

In this work, the 4D_3/2|3,±2⟩→ 4D_5/2|3,±2⟩ transition in the Nb^4+ ion is identified as a promising candidate for a terahertz (THz) atomic clock, with the transition frequency occurring at 56.0224 THz. This transition is primarily driven by the magnetic dipole decay channel, which can easily be accessed by a laser. We focus on the stable ^93Nb isotope, which has 100% natural abundance and a nuclear spin of I=9/2 for experimental advantage. Our data analysis allows us to estimate potential systematic shifts in the proposed clock system, including those due to blackbody radiation, electric quadrupole, second-order Zeeman, and second-order Doppler shifts. The scheme presented in this study can help suppress the AC Stark and electric quadrupole shifts in the clock frequency measurement. All these analyses suggest that the proposed THz atomic clock using Nb^4+ could be valuable in both quantum thermometry and frequency metrology.

The mounting interest in conducting thorough analyses and studies of long-range interactions stems from their wide-ranging applications in cold atomic physics, making it a compelling area for research. In this work, we have evaluated long range van der Waals dispersion (vdW) interactions of Cu and Ag atoms with atoms of group I (Li, Na, K, Rb, Cs, and Fr), II (Be, Mg, Ca, Sr, and Ba), XII (Zn, Cd, and Hg) as well as singly charged ions of group II (Be^+, Mg^+, Ca^+, Sr^+, and Ba^+) and XII (Zn^+, Cd^+, and Hg^+) by calculating C_6(two-body) and C_9 (three-body) vdW dispersion coefficients. In order to obtain these C_6 and C_9 coefficients, we have evaluated the dynamic dipole polarizability of the considered atoms using appropriate relativistic methods and the sum-over-states approach. To ascertain the accuracy of our results, we have compared the evaluated static dipole polarizabilities of Cu and Ag atoms and their oscillator strengths for dominant transitions with available literature. The calculated values of C_6 dispersion coefficients have also been compared with the previously reported results.

We demonstrate that the transition between the fine-structure splitting of the ground state of triply ionized zirconium (Zr IV) is suitable for a terahertz (THz) atomic clock. Its transition frequency is about 37.52 THz and is mainly guided by the magnetic dipole (M1) transition, and it is accessible by a readily available laser. We suggest considering stable even isotopes of Zr and M-J = +/- 1/2 sublevels (i.e., vertical bar 4D(3/2), M-J = +/- 1/2 > -> vertical bar 4D(5/2), M-J = +/- 1/2 > clock transition) for experimental advantage. By performing necessary calculations, we estimate possible systematics due to blackbody radiation and ac Stark, electric quadrupole, and second-order Zeeman shifts along with shifts due to the second-order Doppler effects. The proposed THz atomic clock could be very useful in quantum thermometry and frequency metrology.

We demonstrate transition between the fine structure splitting of the ground state of triply ionized zirconium (Zr IV) is suitable for a terahertz (THz) atomic clock. Its transition frequency is about 37.52 THz and is mainly guided by the magnetic dipole (M1) transition and can be accessible by a readily available laser. We suggest to consider stable even isotopes of Zr and $M_J= \pm 1/2$ sublevels (i.e. $|4D_{3/2},M_J=\pm 1/2\rangle \rightarrow |4D_{5/2},M_J=\pm 1/2\rangle$ clock transition) for the experimental advantage. By performing necessary calculations, we have estimated possible systematics due to blackbody radiation, ac Stark, electric quadrupole and second-order Zeeman shifts along with shifts due to the second-order Doppler effects. The proposed THz atomic clock can be very useful in quantum thermometry and frequency metrology.

Quantum electrometric sensing properties of a four-level system are theoretically investigated for microwave (MW) field measurement in thermal Rydberg atoms. In the considered system, the phenomenon of electromagnetically induced transparency (EIT) is invoked to study the impact of microwave (MW) field strength on its optical response. The amplitude of the MW electric field is obtained directly by measuring the height and frequency of EIT peaks. Further, for MW frequency measurement, the probe spectra are examined for red and blue MW detuned cases. It is found that the responsiveness of 133Cs for MW electric field as well as frequency is relatively higher than 87Rb. The overall sensitivity of both these atoms can be enhanced by the convenient setting of the system and field parameters.

By inferring the dynamic permittivity of different material media from the observations and calculating dynamic electric dipole polarizabilties of the Li through Cs alkali atoms, precise values of $C_3$ coefficients were estimated in Phys. Rev. A {\bf 89}, 022511 (2014) and Phys. Lett. A {\bf 380}, 3366 (2016). Since significant contribution towards the long range van der Waals potential is given by the quadrupole polarization effects, we have estimated the $C_5$ coefficients in this work arising from the quadrupole polarization effects of all the alkali atoms interacting with metal (Au), semiconductor (Si) and four dielectric materials (SiO$_2$, SiN$_x$, YAG and sapphire). The required dynamic electric quadrupole (E2) polarizabilities are evaluated by calculating E2 matrix elements of a large number of transitions in the alkali atoms by employing a relativistic coupled-cluster method. Our finding shows that contributions from the $C_5$ coefficients to the atom-wall interaction potentials are pronounced at short distances (1$-$10 nm). The $C_3$ coefficients of Fr atom interacting with the above material media are also reported. These results can be useful in understanding the interactions of alkali atoms trapped in different material bodies during the high-precision measurements.

Light shift in a state due to the applied laser in an atomic system vanishes at tune-out wavelengths (λTs). Similarly, differential light shift in a transition vanishes at the magic wavelengths (λmagics). In many of the earlier studies, values of the electric dipole (E1) matrix elements were inferred precisely by combining measurements and calculations of λmagic. Similarly, the λT values of an atomic state can be used to infer the E1 matrix element, as it involves dynamic electric dipole (α) values of only one state whereas the λmagic values require evaluation of α values for two states. However, both the λmagic and λT values depend on angular momenta and their magnetic components (M) of states. Here, we report the λmagic and λT values of many S1/2 and D3/2,5/2 states, and transitions among these states of the Mg+, Ca+, Sr+ and Ba+ ions that are independent of M values. It is possible to infer a large number of E1 matrix elements of the above ions accurately by measuring these values and combining with our calculations.

The scalar and tensor components of the electric quadrupole (E2) polarizabilities of the first two excited states of all the alkali-metal atoms are determined. To validate the calculations, we have evaluated the ground state E2 polarizabilities of these atoms and compared them with the literature values. We could not find the ground state E2 polarizability value for Fr in the literature to compare with our result. The dominant parts of these quantities are estimated by combining the precisely calculated E2 transition matrix elements of many low-lying transitions with the experimental energies, while the other contributions are estimated using lower-order methods. Our estimated values for the ground states of the above atoms are in good agreement with the literature values suggesting that our estimated E2 polarizabilities for the excited states of the alkali atoms, which were not known earlier except for the Li atom, are also quite accurate. These reported E2 polarizabilities could be useful in guiding many precision measurements in the alkali atoms.

In the present work, we determine the C5 coefficients along with their uncertainties due to quadrupole polarization effects of all the alkali atoms interacting with a metal (Au), a semiconductor (Si), and four dielectric materials (SiO2, SiNx, yttrium aluminum garnet, and sapphire). The required dynamic electric quadrupole (E2) polarizabilities are evaluated by calculating E2 matrix elements of a large number of transitions in the alkali atoms by employing a relativistic coupled-cluster method. A significant contribution towards the long-range van der Waals potential is made by the quadrupole polarization effects. Our finding shows that contributions from the C5 coefficients to the atom-wall interaction potentials are pronounced at short distances (1-10 nm). The C3 coefficients of a Fr atom interacting with the above material media are also reported. These results could be useful in understanding the interactions of alkali atoms trapped in different material bodies during high-precision measurements.

Study of long-range interactions is increasingly becoming essential due to its various applications in cold atomic physics. These interactions can be conveniently expressed in terms of various dispersion coefficients. In the present work, theoretical calculations have been carried out for the two-dipole (C6), and three-dipole (C9) dispersion coefficients among the group XII atoms and their ions, viz. Zn, Cd, Hg, Zn+, Cd+, and Hg+. To obtain these coefficients, the dynamic dipole polarizabilities and reduced matrix elements required are evaluated using the relativistic methods. Further, using the calculated matrix elements, the oscillator strengths corresponding to leading transitions and static dipole polarizabilities of these atoms and ions are determined for the comparison purposes.

The energy levels arising from the electronic orbital 5p−4f crossing between the ground 5p24f and excited 5p4f2 configurations in the Nd9+ ion are investigated by using high-accuracy relativistic ab initio calculations. The accurate atomic data of the lifetime, gJ factor, electric quadrupole moment, and hyperfine structure of the magnetic dipole are also presented. The long-lived states that are suitable for making narrow-linewidth (milli-Hz) clock lines are found. Dominant systematics caused by stray electromagnetic interactions in an experiment and the coefficients of the relativistic sensitivityto variation of the fine-structure constant α and of the Lorentz invariance violation are evaluated, thus validating that the Nd9+ ion can be a new candidate for high-resolution spectroscopy and precision fundamental studies for probing new physics beyond the Standard Model.

In this work, we present high-accuracy spectroscopic properties, such as line strengths, transition probabilities and oscillator strengths for allowed transitions among nD3/2,5/2,n′S1/2 and n′P1/2,3/2(n=4,n′=5,6) states of Rb-isoelectronic Tc (Tc VII), Ru (Ru VIII) and Rh (Rh IX) ions for their applications in the analysis of astrophysical phenomena occurring inside celestial bodies containing Tc, Ru and Rh ions. Due to the scarcity of computational data of atomic properties of these transitions, as well as considerable discrepancies within the literature about these ions, the precise determination of these properties is necessary. For this purpose, we have implemented relativistic many-body perturbation theory (RMBPT) for evaluation of the wave functions of the considered states. For better accuracy, we have accounted for electron interactions through random phase approximation, Brückner orbitals and structural radiations of wave functions in our RMBPT method for further precise evaluation of electric dipole amplitudes. Combining these values of the observed wavelengths, the above transition properties and radiative lifetimes, a number of excited states of Tc VII, Ru VIII and Rh IX ions have been calculated. For further validation of our work, we have compared our results with the data already available in the literature.

We study the time degradation of quantum information stored in a quantum memory device under a dissipative environment in a parameter range which is experimentally relevant. The quantum memory under consideration is comprised of an optomechanical system with additional Kerr nonlinearity in the optical mode and an anharmonic mechanical oscillator with quadratic nonlinearity. Time degradation is monitored, both in terms of loss of coherence, which is analyzed with the help of Wigner functions, as well as in terms of loss of amplitude of the original state, studied as a function of time. While our time trajectories explore the degree to which the stored information degrades depending upon the variation in values of various parameters involved, we suggest a set of parameters for which the original information can be retrieved without degradation. We identify a very interesting situation where the role played by the nonlinearity is insignificant, and the system behaves as if the information is stored in a linear medium. For this case, the information retrieval is independent of the coherence revival time and can be retrieved at any instant during the time evolution.

Real-time monitoring of harmful gases is of great significance to identify the environmental hazards to people's lives. However, this application scenario requiring low-power consumption, superior sensitivity, portability, and self-driven operation of gas sensors remains a challenge. Herein, an electrospun triboelectric nanogenerator (TENG) is synthesized using highly electronegative and conducting MXene nanofibers (NFs) paired with biodegradable cellulose acetate NFs (CA-NFs) as triboelectric layers, which supports a sufficient power density (∼1361 mW/m2@2 MΩ) and shows a self-powered ability to operate the chemiresistive gas sensor fabricated in this work. Further, by using cellulose nanofibers (C-NFs) as a substrate, a new kind of MXene/TiO2/C-NFs heterojunction-based sensory component is developed for detection of NH3. This sensor exhibits excellent reproducibility, high selectivity, and sensitivity toward NH3 (1-100 ppm) along with a fast response/recovery time (76 s/62 s) at room temperature. Finally, a monitoring system comprising a TENG-powered sensor, an equivalent circuit, and an LED visualizer has been assembled and successfully demonstrated as a fully self-powered device for NH3 leakage detection. Thus, this work pushes forward the intelligent gas sensing network self-driven by human motion energy, dispensing the external battery dependence for environment monitoring to reduce the possible health effects.

We present precise radiative data of line strengths, transition probabilities, and oscillator strengths for the allowed transitions among the nS(1/2), nP(1/2, 3/2), n ' D-3/2,D- 5/2, and n ' F-5/2,F- 7/2 states with n = 4 to 6 and n ' = 4, 5 of the Cu-isoelectronic As, Se, and Br ions. Due to unavailability of precise observations of these spectroscopic data, their accurate estimations are of great interest and useful in analysing various astrophysical phenomena undergoing inside the heavenly bodies that contain As, Se, and Br elements. An all-order perturbative many-body method in the relativistic theory framework has been employed to determine the atomic wave functions, which are further used to estimate the above quantities with the uncertainties. We found significant differences between some of our results and results that are available earlier.