Quantum Electrodynamic Effects Research Articles

Panopticon: not a Transformer, but transforming ion trapping technology

A combination of a hemispherical mirror and unique ion trap design allows for the observation of quantum electrodynamics effects in complex systems.

Theoretical study of the hyperfine interaction constants, Landé g-factors, and electric quadrupole moments for the low-lying states of the 61Ni q+ (q = 11,12,14, and 15) ions* *Project supported by the National Natural Science Foundation of China (Grant Nos. 11704398 and 11934014), the National Key Research and Development Program of China (Grant No. 2017YFA0304402), and the Strategic Priority Research Program

Highly charged nickel ions have been suggested as candidates for the ultra-precise optical clock, meanwhile the relevant experiment has been carried out. In the framework of the multiconfiguration Dirac–Hartree–Fock (MCDHF) method, we calculated the hyperfine interaction constants, the Landé g-factors, and the electric quadrupole moments for the low-lying states in the 61Ni11+, 61Ni12+, 61Ni14+, and 61Ni15+ ions. These states are clock states of the selected clock transitions in highly charged nickel ions (see Fig. ). Based on discussing the effects of the electron correlations, the Breit interaction, and quantum electrodynamics (QED) effect on these physical quantities, reasonable uncertainties were obtained for our calculated results. In addition, the electric quadrupole frequency shifts and the Zeeman frequency shifts of the clock transitions concerned were analyzed.

Non-linear Breit–Wheeler process with linearly polarized beams

We study the non-linear Breit-Wheeler process $\vec \gamma' + \vec L \to e^+ + e^-$ in the interaction of linearly polarized probe photons ($\vec \gamma'$) with a linearly polarized laser beam ($\vec L$). In particular, we consider the asymmetry of the total cross section and the azimuthal electron distributions when the polarizations of the photon and laser beams in the initial state are mutually perpendicular or parallel. Considering intense laser beams and the strong field asymptotic we explore essentially the multi-photon dynamics. The asymmetry exhibits some non-monotonic behavior depending on initial kinematic conditions; it depends sensitively on the laser pulse duration. Our results provide additional knowledge for studying non-linear multi-photon effects in quantum electrodynamics and may be used in planning experiments in upcoming laser facilities.

The Panopticon device: An integrated Paul-trap-hemispherical mirror system for quantum optics.

We present the design and construction of a new experimental apparatus for the trapping of single Ba+ ions in the center of curvature of an optical-quality hemispherical mirror. We describe the layout, fabrication, and integration of the full setup, consisting of a high-optical access monolithic "3D-printed" Paul trap, the hemispherical mirror, a diffraction-limited in-vacuum lens (NA = 0.7) for collection of atomic fluorescence, and a state-of-the art ultra-high vacuum vessel. This new apparatus enables the study of quantum electrodynamics effects such as strong inhibition and enhancement of spontaneous emission and achieves a collection efficiency of the emitted light in a single optical mode of 31%.

Atomic physics at the HIAF under extreme conditions: QED effects from strong Coulomb fields to beyond Schwinger limits

The high-intensity heavy ion accelerator facility (HIAF) is one of the major large-scale research facilities at the nuclear science center planned for Huizhou City in Guangdong Province. HIAF and its experimental terminals can be used to realize unprecedented research progresses in nuclear physics, atomic physics, materials, high-energy-density physics, and applications related to heavy ion beams such as cancer therapy, material modification, and radiobiology. In addition, they will provide excellent possibilities for atomic physics to investigate the quantum electrodynamics (QED) effects from strong electromagnetic fields to super-critical electromagnetic fields beyond the Schwinger limit. Starting from modern atomic spectroscopy based on the accelerator technology and in combination with the beam characteristics of the HIAF, this paper discusses the cutting-edge research topics that could be performed at HIAF and the upgrades to HIAF that could be implemented in the near future. The research fields include the QED effects in super-strong fields, parity nonconservation in highly charged ions, few-body processes in relativistic collisions, and testing the locality of matter waves of massive particles. This paper also discusses the possibility to perform laser spectroscopy with respect to radioactive ions. Furthermore, we believe that the latest high harmonic extreme ultraviolet (XUV) laser technology can be combined with HIAF for realizing high-precision measurements.

Investigation of QED Effects With Varying Z in Thin Foil Targets

Quantum electrodynamics (QED) effects in intense laser–plasma interaction were investigated using particle-in-cell (PIC) simulations, specifically the generation of electron–positron pairs. Linearly polarized intense laser pulses were used to irradiate a thin foil (1- $\mu \text{m}$ ) with an intensity of $4\times 10^{23}$ W cm−2. A scan of targets with varying $Z$ (Al, Cu, and Au) is investigated to determine the effect of target $Z$ /density on electron–positron pair production. The total number of pairs created for Al and Cu targets is 1014 and 1013, respectively. In the case of Au, we did not observe any pair production to occur. We have also calculated the variation in electron energy in these targets. The results indicate that target $Z$ plays a very important role with the laser interaction in the pair production process, which will be explained in this article.

Superradiant Ensembles of Terahertz Polaritonic Meta-Atoms

We experimentally demonstrate the robustness of strong light-matter interaction in an ensemble of terahertz cavities with variable radiation loss. Each cavity in the form of a planar metallic resonator is strongly coupled to intersubband transitions of semiconductor quantum wells. The polariton spectra, measured by time-domain spectroscopy, do not diminish when the cavity ensemble is brought to the superradiant regime with a radiative loss rate increased by a factor of three. In contrast, the splitting of the polariton frequencies gets larger, and indicates an increased vacuum Rabi frequency. We attribute the observed phenomenon to this well-known many-body effect in quantum electrodynamics, but here associated to an ensemble of otherwise independent polariton systems.

Polarized Fock States and the Dynamical Casimir Effect in Molecular Cavity Quantum Electrodynamics.

We present a new theoretical framework, polarized Fock states (PFSs), to describe the coupled molecule-cavity hybrid system in quantum electrodynamics. Through the quantum light-matter interactions under the dipole Gauge, the molecular permanent dipoles polarize the photon field by displacing the photonic coordinate. Hence, it is convenient to use these shifted Fock states (termed the PFSs) to describe light-matter interactions under the strong coupling regimes. These PFSs are nonorthogonal to each other and are light-matter entangled states. They allow an intuitive understanding of several phenomena that go beyond the prediction of the quantum Rabi model, while also offering numerical convenience to converge the results with much fewer states. With this powerful new theoretical framework, we explain how molecular permanent dipoles lead to the generation of multiple photons from a single electronic excitation (down-conversion), effectively achieving the dynamical Casimir effect through the nuclear vibration instead of cavity mirror oscillations.

Dynamic load balancing with enhanced shared-memory parallelism for particle-in-cell codes

Furthering our understanding of many of today’s interesting problems in plasma physics – including plasma based acceleration and magnetic reconnection with pair production due to quantum electrodynamic effects – requires large-scale kinetic simulations using particle-in-cell (PIC) codes. However, these simulations are extremely demanding, requiring that contemporary PIC codes be designed to efficiently use a new fleet of exascale computing architectures. To this end, the key issue of parallel load balance across computational nodes must be addressed. We discuss the implementation of dynamic load balancing by dividing the simulation space into many small, self-contained regions or “tiles,” along with shared-memory (e.g., OpenMP) parallelism both over many tiles and within single tiles. The load balancing algorithm can be used with three different topologies, including two space-filling curves. We tested this implementation in the code Osiris and show low overhead and improved scalability with OpenMP thread number on simulations with both uniform load and severe load imbalance. Compared to other load-balancing techniques, our algorithm gives order-of-magnitude improvement in parallel scalability for simulations with severe load imbalance issues.

Cavity quantum electro-dynamics with solid-state emitters in aperiodic nano-photonic spiral devices

Integrated quantum devices are at the basis of the realization of scalable, high-performance quantum technology, including quantum computers and quantum communication schemes, where single photons are emitted, guided, manipulated, and detected on a chip. Engineered nano-devices enable the efficient confinement of light and, ultimately, the control of the spontaneous emission dynamics of single emitters, which is crucial for cavity quantum electrodynamics experiments and for the development of classical and quantum light sources. Here, we report on the demonstration of enhanced light-matter interaction and Purcell effects on a chip, based on bio-inspired aperiodic devices fabricated in gallium arsenide. Indium arsenide single quantum dots are used as internal light sources to image, by means of micro-photoluminescence spectroscopy, the optical modes supported by photonic membranes with Vogel-spiral geometry. These emitters are also used to probe the density of optical states, modified by the aperiodic devices, by means of time-resolved spectroscopy. Our results show cavity quantum electrodynamics effects providing strong modifications of the spontaneous emission decay of single optical transitions. In particular, thanks to the significant modification of the density of optical states demonstrated in Vogel-spiral photonic structures, we show control of the decay lifetime of single emitters with a dynamic range reaching 20, thus opening the path to the implementation of aperiodic geometries in active classical and quantum devices.

Measurement of the P1/22−P3/22 fine-structure splitting in fluorinelike Kr, W, Re, Os, and Ir

Quantum electrodynamics (QED) is currently considered to be one of the most accurate theories of fundamental interactions. As its extraordinary precision offers unique scientific opportunities, e.g., search for new physics, stringent experimental tests of QED continue to be of high importance. To this end, highly charged ions represent an exceptional test-bed due to enhanced QED effects. Recently, forbidden transitions in F-like ions have been analyzed to few ppm precision, resolving previous discrepancies between theory and experiment. Here we further test the accuracy of QED calculations with three new (Re, Os, Ir), and two improved (Kr, W) measurements of the $^{2}P_{1/2}\text{\ensuremath{-}}^{2}P_{3/2}$ transition energy in F-like ions using the NIST electron-beam ion trap and extreme-ultraviolet and x-ray spectrometers. Good agreement between theoretical and experimental energies is found for all considered elements.

Overview of ELI-NP status and laser commissioning experiments with 1 PW and 10 PW class-lasers

In the last decade, the laser intensity has reached up to 1021 Wcm−2 on focus allowing the generation of new phenomena, which are relevant not only in basic physics research but also in applied science with great benefit to the society. In this regard, in 2006, the Extreme Light Infrastructure project was considered in the roadmap of ESFRI with the aim of creating European research centers for cutting-edge studies. From the three pillars under development, the Romanian one, denominated ELI-NP (Extreme Light Infrastructure Nuclear Physics), will be broadly studying the laser-plasma interaction by employing a 10 PW class-laser with the intent of studying the behavior of matter exposed at extreme light intensities and consequently producing specific ion and gamma-ray sources of relevance for nuclear physics. For instance, phenomena like the Target Normal Sheath Acceleration (TNSA) and the Radiation Pressure Acceleration (RPA) will be widely investigated in a new regime in which Quantum electrodynamics (QED) effects start to play a significant role. Particle-In-Cell (PIC) simulations and theoretical models predict ion beams with energies up to sub-GeV/u and gamma-ray pulses of the order of few petawatts from a 10 PW laser beam (i.e. laser intensity of about 1023 Wcm−2). Further, multi-GeV electron beams of quality suitable for applications are expected to be attained from gas targets via LWFA (Laser Wakefield Acceleration). The active investigation which will be pursued in the coming years at ELI-NP will certainly bring to the discovery of novel physics phenomena and several applications. The commissioning of the experimental areas dedicated to research with high power lasers and a gradual entering in operation will take place during 2020–2021.

Systematic calculations of energy levels and transitions rates in Mo XXVIII

Abstract Complete and consistent atomic data, including excitation energies, lifetimes, wavelengths, hyperfine structures, Landé g J -factors and E1, E2, M1, and M2 line strengths, oscillator strengths, transitions rates are reported for the low-lying 41 levels of Mo XXVIII, belonging to the n = 3 states (1s 22s 22p 6)3s 23p 3, 3s3p 4, and 3s 23p 23d. High-accuracy calculations have been performed as benchmarks in the request for accurate treatments of relativity, electron correlation, and quantum electrodynamic (QED) effects in multi-valence-electron systems. Comparisons are made between the present two data sets, as well as with the experimental results and the experimentally compiled energy values of the National Institute for Standards and Technology wherever available. The calculated values including core-valence correction are found to be in a good agreement with other theoretical and experimental values. The present results are accurate enough for identification and deblending of emission lines involving the n = 3 levels, and are also useful for modeling and diagnosing plasmas.

Threshold Photodetachment Spectroscopy of the Positronium Negative Ion.

Threshold photodetachment spectroscopy of the positronium negative ion has been accomplished for the first time employing an efficient source of the ions and photodetachment techniques combined with a tunable optical parametric oscillator and amplifier laser. The photodetachment threshold, corresponding to the electron affinity of positronium (1^{3}S_{1}), was determined to be 326.88±0.09(stat)±0.10(syst) meV by laser photodetachment threshold measurements. This result is consistent with a variational calculation corrected for leading relativistic and quantum electrodynamical effects.

Quasilocalized dynamics from confinement of quantum excitations

Confinement of excitations induces quasilocalized dynamics in disorder-free isolated quantum many-body systems in one spatial dimension. This occurrence is signalled by severe suppression of quantum correlation spreading and of entanglement growth, long-time persistence of spatial inhomogeneities, and long-lived coherent oscillations of local observables. In this work, we present a unified understanding of these dramatic effects. The slow dynamical behavior is shown to be related to the Schwinger effect in quantum electrodynamics. We demonstrate that it is quantitatively captured for long time scales by effective Hamiltonians exhibiting Stark localization of excitations and weak growth of the entanglement entropy for arbitrary coupling strength. This analysis explains the phenomenology of real-time string dynamics investigated in a number of lattice gauge theories, as well as the anomalous dynamics observed in quantum Ising chains after quenches. Our findings establish confinement as a robust mechanism for hindering the approach to equilibrium in translationally-invariant quantum statistical systems with local interactions.

QED calculation of ionization energies of 1snd states in helium

Quantum electrodynamical (QED) calculations of ionization energies of the $1snd\,D$ states are performed for the helium atom. We reproduce the previously known relativistic and QED effects up to order $m\alpha^5$ and extend the theory by calculating the complete $m\alpha^6$ correction. The total contribution of the $m\alpha^6$ effects is shown to be much smaller than previously estimated, due to a large cancelation between the radiative and non-radiative parts of this correction. As a result of our calculations, we confirm the previously reported deviations between measured transition energies and theoretical predictions for the $nD$--$2S$ and $nD$--$2P$ transitions. Possible reasons for this discrepancy are analyzed.

MCDHF/RCI extended calculations of energy levels, radiative properties, [formula omitted], [formula omitted] hyperfine interaction constants, and Landé [formula omitted]-factors for [formula omitted][formula omitted

Energy levels, weighted oscillator strength, transition probabilities, AJ, BJ hyperfine interaction constants, and Landé gJ-factors have been calculated for all levels of 1s2 and 1snl (n=1−7, 0≤l≤n−1) configurations of He-like Argon ion (ArXVII). Multiconfigurational Dirac-Hartree-Fock (MCDHF) method has been adopted for calculating the mentioned parameters. Transition probabilities are reported for all allowed and forbidden transitions (E1, E2, M1 and M2) from the ground level. Breit interactions and quantum electrodynamics effects are estimated in subsequent relativistic configuration interaction calculations (RCI). The present calculations, namely MCDHF/RCI, have been compared with other theoretical results. Our results are in reasonable agreement with the published experimental data and theoretical values. Also, lifetimes for all excited levels were calculated. Most of the data presented here are published for the first time.

Accurate Treatment of Comptonization in X-Ray Illuminated Accretion Disks

Abstract A large fraction of accreting black hole and neutron star systems present clear evidence of the reprocessing of X-rays in the atmosphere of an optically thick accretion disk. The main hallmarks of X-ray reflection include fluorescent K-shell emission lines from iron (∼6.4–6.9 keV), the absorption iron K-edge (∼7–9 keV), and a broad featureless component known as the Compton hump (∼20–40 keV). This Compton hump is produced as the result of the scattering of high-energy photons (E ≳ 10 keV) of the relatively colder electrons (T e ∼ 105–107 K) in the accretion disk, in combination with photoelectric absorption from iron. The treatment of this process in most current models of ionized X-ray reflection has been done using an approximated Gaussian redistribution kernel. This approach works sufficiently well up to ∼100 keV, but it becomes largely inaccurate at higher energies and at relativistic temperatures (T e ∼ 109 K). We present new calculations of X-ray reflection using a modified version of our code xillver, including an accurate solution for Compton scattering of the reflected unpolarized photons in the disk atmosphere. This solution takes into account quantum electrodynamic and relativistic effects allowing the correct treatment of high photon energies and electron temperatures. We show new reflection spectra computed with this model, and discuss the improvements achieved in reproducing the correct shape of the Compton hump, the discrepancies with previous calculations, and the expected impact of these new models in the interpretation of observational data.

Nonradiative α7m QED effects in the Lamb shift of helium triplet states

Theoretical predictions for the Lamb shift in helium are limited by unknown quantum electrodynamic effects of the order $\alpha^7m$, where $\alpha$ is the fine-structure constant and $m$ is the electron mass. We make an important step towards the complete calculation of these effects by deriving the most challenging part, which is induced by the virtual photon exchange between all three helium particles, the two electrons, and the nucleus. The complete calculation of the $\alpha^7m$ effect including the radiative corrections will allow comparing of the nuclear charge radii determined from the electronic and muonic helium atoms and thus provide a stringent test of the Standard Model of fundamental interactions.

Energy levels, weighted oscillator strengths, transition rates, lifetimes of He-like-Pt deduced from the relativistic multiconfiguration Dirac–Hartree–Fock and relativistic configuration interaction theory calculations

We disclose relativistic multiconfiguration Dirac–Hartree–Fock (MCDHF) spectrum calculations for He-like-Pt. Energy levels and weighted oscillator strengths are calculated for 127 odd- and even-parity states as well as lifetimes and transition rates between these states. For comparative purpose, we have implemented parallel calculations using a Flexible Atomic Code (FAC) by introducing the relativistic configuration interaction (RCI) method. Additionally, the Breit interaction and leading quantum electrodynamics effects (QED) are included as perturbations in extensive RCI calculations. We signal that, our calculations for He-like-Pt are made for the first time and they provide to date the most accurate and complete atomic data related to this ion.