Quantum Electrodynamic Effects Research Articles

Relativistic theoretical calculations of singly and doubly energy levels, lifetimes, wavelengths, weighted oscillator strengths and radiative rates for Helium-Like Ions with [formula omitted]

We provide accurate energy levels for the lowest singly excited 70 levels among 1snl(n≤6,l≤(n−1)) configurations and the lowest doubly excited 250 levels arising from the K-vacancy 2ln′l′(n′≤6,l′≤(n′−1)) configurations of helium-like ions with Z=5−9. Wavelengths, weighted oscillator strengths and transition rates for electric-multipole (dipole (E1), quadrupole (E2)) and magnetic-multipole (dipole (M1), quadrupole (M2)) are also calculated. The lifetimes determinations are reported for all the calculated levels. The calculations were performed using the Relativistic Configuration Interaction (RCI) method implemented in the Flexible Atomic Code (FAC). For comparative purposes, the second set of calculations was obtained with other packages of programs for relativistic atomic structure calculations (AMBiT) based on a method combining many-body perturbation theory and configuration interaction (CI). Additionally, the Breit interaction and leading quantum electrodynamics effects (QED) are included. Our results are compared with other available theories reported in the literature as well as the data taken from NIST online database. A good agreement between them has been found. We signal that our calculations for the doubly excited levels are made for the first time and they provide accurate and complete atomic data on these ions. Our results can contribute to the NIST database by essentially extending the data for doubly excited states.

Evidence for near-unity radiative quantum efficiency of bright excitons in carbon nanotubes from the Purcell effect

The efficiencies of photonic devices are primarily governed by radiative quantum efficiency, which is a property given by the light-emitting material. Quantitative characterization for carbon nanotubes, however, has been difficult despite being a prominent material for nanoscale photonics. Here we estimate the radiative quantum efficiency of bright excitons in carbon nanotubes by modifying the exciton dynamics through cavity quantum electrodynamical effects. Silicon photonic crystal nanobeam cavities are used to induce the Purcell effect on individual carbon nanotubes. Spectral and temporal behavior of the cavity enhancement is characterized by photoluminescence microscopy and the fraction of the radiative decay process is evaluated. We find that the radiative quantum efficiency can reach near unity for bright excitons in long air-suspended carbon nanotubes at room temperature.Received 19 March 2021Revised 27 February 2022Accepted 23 March 2022DOI:https://doi.org/10.1103/PhysRevResearch.4.L022011Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasCavity quantum electrodynamicsExcitonsPhysical SystemsNanotubesOptical microcavitiesTechniquesPhotoluminescenceCondensed Matter, Materials & Applied Physics

Accurate multiconfiguration calculations of energy levels, transition rates, and lifetimes for Kr XXIII

Extensive Multiconfiguration Dirac-Hartree-Fock calculations are performed for the lowest 97 levels belonging to the 3s23p2, 3s3p3, 3s23p3d, 3s3p23d, 3s23d2, and 3p4 configurations in silicon-like Kr XXIII. Complete and consistent data sets of energy levels, transition rates and lifetimes for electric-dipole (E1), electric-quadrupole (E2), magnetic-dipole (M1), and magnetic-quadrupole (M2) transitions among all these levels are given. High-accuracy calculations have been performed with accurate treatment of relativity, electron correlation, and quantum electrodynamic effects, as well as inter-electron correlation. The calculated energy levels are in excellent agreement with available theoretical and experimental data. The present results are reported as benchmarks for future calculations and measurements.

All-optical dynamic modulation of spontaneous emission rate in hybrid optomechanical emitter-cavity systems

Optomechanics is the study of the interaction between nano-objects and light fields through radiation pressure. Recent sophisticated optomechanical systems consist of strongly coupled mechanical and optical resonators and are made using semiconductor nanofabrication techniques. Although the optomechanical systems have exhibited their powerful capability of controlling photons, they are scarcely used to control the solid-state artificial atoms that emit photons. The main reason is that an efficient coupling mechanism remains unexplored. Here, we hybridize a silicon-integrated optomechanical resonator with two-level atom-like emitters to demonstrate an optomechanical cavity quantum electrodynamic (cQED) effect. With this system and the effect, we realize the dynamic modulation of the spontaneous emission rate. We choose copper dopants in silicon as the emitters for its narrow linewidth (0.3 nm) and long lifetime ( ∼ 30 n s ). Our judiciously designed coupled-nanobeam optomechanical resonator achieves a strong Purcell effect and high cavity-modulation performances. The optical cavity of the optomechanical resonator is dynamically coupled to the emission line and, as a result, on-demand sharp pulses (up to 9.5-fold intensity enhancement and 3.5 ns in duration, which is one ninth of the emission lifetime) appear along the photoluminescence decay. These experimental results are exactly explained with an analytical model that combines optomechanical and cQED theories. Considering that dopants in silicon are highly competitive qubits, we believe that our optomechanical cQED technology will find important applications in the quantum era.

An Investigation on Electric Dipole Transitions of Pt LXVII

In the present work, we have reported the energy levels, wavelengths, weighted oscillator strengths, and transition probabilities for electric dipole (E1) transitions of magnesium like platinum (Pt LXVII, Z=78). Accurate knowledge of Mg-like ions are of great importance for astrophysics, plasma, and thermonuclear fusion research. The atomic data are calculated with the AUTOSTRUCTURE code, where relativistic corrections are introduced according to the Breit–Pauli distorted wave approach. In the calculations, quantum electrodynamics effects and correlation contributions have been considered. The present results are in good agreement with other available values. There are no experimental works for Pt LXVII in the literature. We predict new theoretical data for several levels will be helpful for future experimental works.

Relativistic excitation energies and transition data for In XL and Sn XLI

Excitation energies, lifetimes, and level designations in jj- and LS-coupling schemes are computed for the lowest 139 fine-structure levels belonging to the 2s22p6, 2s22p5nl (n = 3 − 5, l = 0 − 4), and 2s2p6nl (n = 3 − 4, l = 0 − 3) configurations in Ne-like In XL and Sn XLI. Wavelengths, weighted oscillator strengths, transition probabilities, and line strengths are calculated for allowed and forbidden transitions including electric dipole (E1), electric quadrupole (E2), magnetic dipole (M1), and magnetic quadrupole (M2) transitions. The computations are done with the fully relativistic multiconfiguration Dirac-Hartree-Fock (MCDHF) method, which incorporates the Breit-interaction (BI) and quantum electrodynamics (QED) effects. The present results are compared to available experimental and other theoretical data in order to determine the accuracy of results.

Abinitio determination of the polarizability of neon

The static electric-dipole polarizability $\ensuremath{\alpha}$ of the neon atom was determined with a relative uncertainty of only about 0.003% using state-of-the-art ab initio approaches. The new value, $\ensuremath{\alpha}=2.661\phantom{\rule{0.16em}{0ex}}067(77)\phantom{\rule{0.16em}{0ex}}\mathrm{a}.\mathrm{u}.$, is almost five times more accurate than the previous ab initio estimate, $\ensuremath{\alpha}=2.660\phantom{\rule{0.16em}{0ex}}80(36)\phantom{\rule{0.16em}{0ex}}\mathrm{a}.\mathrm{u}.$, by Lesiuk et al. [Phys. Rev. A 102, 052816 (2020)]. Similar to their work, we calculated $\ensuremath{\alpha}$ using ab initio methods up to full configuration interaction and added corrections for finite nuclear mass and size, relativistic, and quantum electrodynamics (QED) effects. The uncertainty reduction of this work was achieved in particular by employing extremely large basis sets, including newly developed ones of 11Z, 12Z, and 13Z quality. Moreover, the finite nuclear mass effects and most of the relativistic contributions were calculated at much higher levels of theory than in the work of Lesiuk et al. However, we adopted their values for the orbit-orbit part of the relativistic correction and for the Bethe logarithm needed to compute the QED correction. The uncertainty of our final value is still an order of magnitude larger than that of the experimental value recently measured by Gaiser and Fellmuth [Phys. Rev. Lett. 120, 123203 (2018)] with an uncertainty of only a few parts per million using dielectric-constant gas thermometry. Yet, our ab initio value agrees with their value, ${\ensuremath{\alpha}}_{\mathrm{exp}}=2.661\phantom{\rule{0.16em}{0ex}}057(7)\phantom{\rule{0.16em}{0ex}}\mathrm{a}.\mathrm{u}.$, almost within the experimental uncertainty. This could indicate that the higher-order relativistic corrections and QED contributions, which dominate our uncertainty budget, are more accurate than expected considering the uncontrolled approximations involved in their calculation.

Electron Impact Excitation of Ge-like Te20+–Cd16+ Ions

We study electron impact excitation of dipole allowed transitions in the extreme ultraviolet range—8–55 nm—for the germanium isoelectronic sequence Te20+–Cd16+. The fine structure transitions between the ground state having configuration 4s24p2 and the excited states with configurations 4s4p3 and 4s24p4d are considered for these ions. We employ the relativistic distorted wave method to calculate the excitation cross sections in the incident electron energy range from the excitation threshold to 5000 eV. To obtain the required ionic bound state wavefunctions we have used the multi-configuration Dirac-Fock method with correlations within the n = 5 complexes as well as performed relativistic configuration interaction calculations to include the quantum electrodynamic effects. The accuracy of these wavefunctions is established by comparing our calculated wavelengths and oscillator strengths of the considered transitions with the previously reported measurements and other available theoretical results. We also provide the fitting parameters of the calculated cross sections and the excitation rate coefficients for their direct applications in plasma modeling.

Fitting XMM-Newton observations of the AXP 1RXS J170849.0−400910 with four magnetar surface emission models, and predictions for X-ray polarization observations with IXPE

Context. Phase-resolved spectral and spectropolarimetric X-ray observations of magnetars present us with the opportunity to test models of the origin of the X-ray emission from these objects, and to constrain the properties of the neutron star surface and atmosphere. Aims. Our first aim is to use archival XMM-Newton observations of the magnetar 1RXS J170849.0−400910 to ascertain how well four emission models describe the phase-resolved XMM-Newton energy spectra. Our second aim is to evaluate the scientific potential of future spectropolarimetric observations of 1RXS J170849.0−400910 with the Imaging X-ray Polarimetry Explorer (IXPE) scheduled for launch in late 2021. The most salient questions are whether IXPE is able to distinguish between the different emission models, and whether IXPE can unambiguously detect the signatures of quantum electrodynamics (QED) effects in strong magnetic fields. Methods. We used numerical radiation transport calculations for a large number of different system parameters to predict the X-ray flux and polarization energy spectra of the source 1RXS J170849.0−400910. Based on the numerical results, we developed a new model to fit phase-resolved and phase-averaged X-ray spectral (i.e., XMM-Newton and IXPE) and spectropolarimetric (IXPE) data. In order to test the sensitivity of IXPE to strong-field QED effects, we fit a simulated IXPE observation with two versions of the model, i.e., with and without QED effects accounted for. Results. The fixed-ions condensed surface model gives the best description of the phase-resolved XMM-Newton spectra, followed by the blackbody and free-ions condensed surface models. The magnetized atmosphere model gives a poor description of the data and seems to be largely excluded. Simulations show that the IXPE observations of sources such as 1RXS J170849.0−400910 will allow us to cleanly distinguish between high-polarization (blackbody, magnetized atmosphere) and low-polarization (condensed surface) models. If the blackbody or magnetized atmosphere models apply, IXPE can easily prove QED effects based on ∼200 ksec observations as studied here; longer IXPE observation times will be needed for a clear detection in the case of the condensed surface models. Conclusions. The XMM-Newton data have such a good signal-to-noise ratio that they reveal some limitations of the theoretical models. Notwithstanding this caveat, the fits clearly favor the fixed-ions condensed surface and blackbody models over the free-ions condensed surface and magnetized atmosphere models. The IXPE polarization information will greatly help us to figure out how to improve the models. The first detection of strong-field QED effects in the signal from astrophysical sources seems possible if an adequate amount of time is dedicated to the observations.

Theoretical evaluation of excitation cross section and fluorescence polarization of a solid-density Si plasma

In this article, a fully relativistic approach is proposed to precisely predict the electronic structures, spectral properties, cross sections, and degrees of linear polarization of light emitted after excitation of plasma-embedded ions by electron impact, taking into account the plasma shielding effects on the atomic structures and collision dynamics, in addition to the contributions of Breit interaction and quantum electrodynamics effects. The scheme employs the effective shielding potential deduced from a solution of Poisson equation, based on the self-consistent field ion-sphere simulations to explain the interactions among the charged particles, where the perturbation correlation Dirac–Coulomb Hamiltonian is constructed. The simple and understandable form makes it a good substitute for complex self-consistent field calculation. As an illustrative example, a comparative investigation regarding the influences of different plasma temperature and density parameters on the level energies, transition rates, integrated total/magnetic sublevel cross sections, and linear polarizations of the radiation following electron-impact excitation of Si XIII (a solid-density Si plasma) is carried out. Numerical results show that the plasma density effect can significantly affect the atomic structures and collision cross sections, yet has limited influence on the polarization characteristics. A comparison of our calculations with other results, when available, is made. The advanced approach presented here not only opens a novel window for exploring the atomic dynamics processes in hot and/or dense plasmas, but also provides important information about polarization of the line emission. This study is beneficial for the high energy density physics, laser-produced plasmas, and astrophysical applications.

Hilbert space fragmentation produces an effective attraction between fractons

Fracton systems exhibit restricted mobility of their excitations due to the presence of higher-order conservation laws. Here we study the time evolution of a one-dimensional fracton system with charge and dipole moment conservation using a random unitary circuit description. Previous work has shown that when the random unitary operators act on four or more sites, an arbitrary initial state eventually thermalizes via a universal subdiffusive dynamics. In contrast, a system evolving under three-site gates fails to thermalize due to strong ``fragmentation'' of the Hilbert space. Here we show that three-site gate dynamics causes a given initial state to evolve toward a highly nonthermal state on a timescale consistent with Brownian diffusion. Strikingly, the dynamics produces an effective attraction between isolated fractons or between a single fracton and the boundaries of the system, as in the Casimir effect of quantum electrodynamics. We show how this attraction can be understood by exact mapping to a simple classical statistical mechanics problem, which we solve exactly for the case of an initial state with either one or two fractons.

Quantum electrodynamic effects on counter-streaming instabilities in the whole k space.

In a recent work [Bret, EPL 135, 35001 (2021)10.1209/0295-5075/ac1e44], quantum electrodynamic (QED) effects were evaluated for the two-stream instability. It pertains to the growth of perturbations with a wave vector oriented along the flow in a collisionless counter-streaming system. Here, the analysis is extended to every possible orientation of the wave vector. The previous result for the two-stream instability is recovered, and it is proved that, even within the framework of a three-dimensional (3D) analysis, this instability remains fundamentally 1D even when accounting for QED effects. The filamentation instability, found for wave vectors normal to the flow, is weakly affected by QED corrections. As in the classical case, its growth rate saturates at large k_{⊥}. The saturation value is found independent of QED corrections. Also, the smallest unstable k_{⊥} is independent of QED corrections. Surprisingly, unstable modes found for oblique wave vectors do not follow the same pattern. For some, QED corrections do reduce the growth rate. But, for others, the same corrections increase the growth rate instead. The possibility for QED effects to play a role in unmagnetized systems is evaluated. Pair production resulting from γ emission by particles oscillating in the exponentially growing fields is not accounted for.

Ionization energy and valence electron orbital binding energy of superheavy element Og(<i>Z</i> = 118) and its homologs

The ionization energy of the superheavy element Og (<i>Z</i> = 118) and its homolog elements Ar, Kr, Xe, Rn, and their ions are systematically calculated by using the GRASP2K program based on the multi-configuration Dirac-Hartree-Fock (MCDHF) method, taking into account relativistic effects, electron correlation effects between valence shell electrons, quantum electrodynamics effects, and Breit interaction. To reduce the uncertainty of the ionization energy derived from electron correlation effects which are not fully considered, the ionization potential of the superheavy element Og<sup>0–2+</sup> and its homolog element Rn<sup>0–2+</sup> are extrapolated by the extrapolation method. The ionization energy of extrapolated Rn<sup>0–5+</sup> and Og<sup>5+</sup> coincide well with experimental and other theoretical values. These results can be used to predict the unknown physical and chemical properties of the atoms and compounds of the superheavy element Og. In addition, the calculation results of the electron orbital binding energy of the atomic valence shell of the superheavy element Og and its homolog elements Ar, Kr, Xe, and Rn under relativistic and non-relativistic conditions show that owing to the relativistic effect, there occur strong orbital contraction phenomena in the 7s orbital and 7p<sub>1/2</sub> orbital and strong splitting phenomena in the 7p<sub>1/2 </sub> orbital and 7p<sub>3/2</sub> orbital of Og, which may cause the physical and chemical properties of the superheavy element Og to differ from those of other homologs.

Fabrication, testing, and assembly of high-finesse optical fiber microcavity for molecule cavity QED experiment

The ultracold molecule is a promising candidate for versatile quantum tasks due to its long-range interaction and rich internal rovibrational states. With the help of the cavity quantum electrodynamics (QED) effects, an optical cavity can be employed to increase the efficiency of the formation of the photoassociated molecules and offers a non-demolition detection of the internal states of molecules. Here, we demonstrate the production of the high-finesse optical fiber microcavity for the Rb2 molecule cavity QED experiment, which includes the fabrication of fiber-based cavity mirrors, testing, and the assembly of ultra-high vacuum-compatible optical fiber microcavity. The optical fiber microcavity offers high cooperativity between cavity mode and ultracold molecule and paves the way for the study of molecule cavity QED experimental research.

Ionization energy and valence electron orbital binding energy of the superheavy element Og(Z=118) and its homologs

The ionization energy of the superheavy element Og (Z=118) and its homolog elements Ar, Kr, Xe, Rn, and their ions were systematically calculated using the GRASP2K program based on the multi-configuration Dirac-Hartree-Fock (MCDHF) method, taking into account relativistic effects, electron correlation effects between valence shell electrons (VV), quantum electrodynamics (QED) effects, and Breit interaction. To reduce the uncertainty of the ionization energy derived from electron correlation effects which are not fully considered, the ionization potential of the superheavy element Og<sup>0-2+</sup> and its homolog element Rn<sup>0-2+</sup> are extrapolated by the extrapolation method. The ionization energy of extrapolated Rn<sup>0-5+</sup> and Og<sup>5+</sup> coincides well with experimental and other theoretical values. These results can be used to predict the unknown physical and chemical properties of the atoms and compounds of the superheavy element Og. In addition, the calculation of the electron orbital binding energy of the atomic valence shell of the superheavy element Og and its homolog elements Ar, Kr, Xe, and Rn under relativistic and non-relativistic conditions shows that due to the relativistic effect, there is a strong orbital contraction phenomenon in the 7s and 7p<sub>1/2</sub> orbitals and a strong splitting phenomenon occurs in the 7p<sub>1/2</sub>and 7p<sub>3/2</sub> orbitals of Og, which may cause the physical and chemical properties of the superheavy element Og to be different from other homologs.

Ultralow-threshold six-photon-excited upconversion lasing in a plasmonic microcavity.

Nonlinear multiphoton absorption (MPA) upconversion lasers have critical applications in fluorescence imaging probes and biological photonics. Here, we report the realization of ultralow-threshold six-photon-excited upconversion lasing through cavity quantum electrodynamics effects in a plasmonic microcavity. The value of the Purcell factor (Fp) in hybrid whisper-gallery mode (WGM) is enhanced five-fold relative to a bare microwire (MW), which enhances the nonlinear light-matter interactions dramatically. Compared with a MW, the threshold of six-photon upconversion WGM lasing is reduced by one order magnitude due to plasmonic enhancement effects. In addition, the temperature and polarization characteristics of upconversion lasing via a plasmonic-WGM approach show a distinct evolution, different from a bare MW. This work paves the way for extreme nonlinear optics, taking advantage of the processability and high Purcell factor of plasmonic microcavities.

Spectral calibration for electron beam ion trap and precision measurement of M1 transition wavelength in Ar<sup>13+</sup>

The precise measurement of the transition wavelength of the fine structure of highly charged ions can not only test basic physical theories including the quantum electrodynamics effect and the electronic correlation effect but also provide key atomic data for astrophysics and fusion plasma physics. Furthermore, highly charged ions are considered as a potential candidate for optical clocks with extremely ultra-high precision. In this work, a new spectral calibration system is built in a high-temperature superconducting electron beam ion trap (SH-HtscEBIT) in the Institute of Modern Physics, Fudan University, and the uncertainty of its spectrum wavelength measurement is evaluated by combining internal and external calibrations. The minimum wavelength uncertainty caused by the new spectral calibration system in the visible light band reaches 0.002 nm. On this basis, the precise measurement of 2s<sup>2</sup>2p <sup>2</sup>P<sub>1/2</sub>－<sup>2</sup>P<sub>3/2</sub> M1 transition wavelength for boron-like Ar<sup>13+</sup> is performed at the SH-HtscEBIT by utilizing the new calibration system. The experimentally measured transition wavelength is (441.2567 ± 0.0026) nm. It is currently the experimental result with the highest measurement accuracy of spectroscopy of highly charged ions at the SH-HtscEBIT, which lays the foundation for the precise measurement of the hyperfine splitting and isotope shift of highly charged ions in the future experiments.

Higher fidelity simulations of nonlinear Breit\u2013Wheeler pair creation in intense laser pulses

When a photon collides with a laser pulse, an electron-positron pair can be produced via the nonlinear Breit–Wheeler process. A simulation framework has been developed to calculate this process, which is based on a ponderomotive approach that includes strong-field quantum electrodynamical effects via the locally monochromatic approximation (LMA). Here we compare simulation predictions for a variety of observables, in different physical regimes, with numerical evaluation of exact analytical results from theory. For the case of a focussed laser background, we also compare simulation with a high-energy theory approximation. These comparisons are used to quantify the accuracy of the simulation approach in calculating harmonic structure, which appears in the lightfront momentum and angular spectra of outgoing particles, and the transition from multi-photon to all-order pair creation. Calculation of the total yield of pairs over a range of intensity parameters is also used to assess the accuracy of the locally constant field approximation (LCFA).

Multiconfiguration Dirac–Hartree–Fock calculations of energy levels, wavelengths, weighted oscillator strengths, transitions probabilities and lifetimes of Cd XLVII

Abstract Energy levels, wavelengths, weighted oscillator strengths, transition probabilities and lifetimes are calculated for all levels of 1s 2 and 1snl (n = 2–6) configurations of He-like cadmium ion (Cd XLVII). The calculations were carried out using three codes GRASP2018, FAC and AMBiT in order to provide theoretically the most accurate data. Transition probabilities are reported for all the E1, E2, M1 and M2 transitions. Breit interactions and quantum electrodynamics effects are included in the RCI calculations. Comparisons were made with other calculations and a good agreement was found which confirms the reliability of our results. We present some missing data for the He-like cadmium in this paper for the first time.

Theoretical investigation of energy levels and transition rates in Mo XXIX

The Multiconfiguration Dirac-Hartree-Fock method is used to calculate energy levels, radiative rates and lifetimes for electric-dipole (E1), electric-quadrupole (E2), magnetic-dipole (M1), and magnetic-quadrupole (M2) transitions among the lowest 97 levels belonging to the 3s23p2, 3s3p3, 3s23p3d, 3s3p23d, 3s23d2, and 3p4 configurations in silicon-like Mo XXIX. High-accuracy calculations have been performed with accurate treatment of relativity, electron correlation, and quantum electrodynamic effects, as well as inter-electron correlation. The calculated energy levels are in excellent agreement with available experimental data. The present results are reported as benchmarks for future calculations and measurements.