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The emerging field of quantum simulation of many-body systems is widely recognized as a very important application of quantum computing. A crucial step towards its realization in the context of many-electron systems requires a rigorous quantum mechanical treatment of the different interactions. In this pilot study, we investigate the physical effects beyond the mean-field approximation, known as electron correlation, in the ground state energies of atomic systems using the classical-quantum hybrid variational quantum eigensolver algorithm. To this end, we consider three isoelectronic species, namely Be, Li−, and B+. This unique choice spans three classes—a neutral atom, an anion, and a cation. We have employed the unitary coupled-cluster ansätz to perform a rigorous analysis of two very important factors that could affect the precision of the simulations of electron correlation effects within a basis, namely mapping and backend simulator. We carry out our all-electron calculations with four such basis sets. The results obtained are compared with those calculated by using the full configuration interaction, traditional coupled-cluster and the unitary coupled-cluster methods, on a classical computer, to assess the precision of our results. A salient feature of the study involves a detailed analysis to find the number of shots (the number of times a variational quantum eigensolver algorithm is repeated to build statistics) required for calculations with IBM Qiskit’s QASM simulator backend, which mimics an ideal quantum computer. When more qubits become available, our study will serve as among the first steps taken towards computing other properties of interest to various applications such as new physics beyond the Standard Model of elementary particles and atomic clocks using the variational quantum eigensolver algorithm.

We present an extension and a deepened analysis of a suggested experimental scheme for detecting atomic parity violation, previously published in Phys. Rev. A 2019, 100, 050101. The experimental concept is described in more detail and we compute new ab initio data necessary for assessing the plausibility of the approach. Original theoretical data for transition matrix elements on the electric dipole forbidden transition in caesium 6 s 2 S M M 1 / 2 &ndash, 5 d 2 D M M 3 / 2 are reported, as are a range of electric dipole matrix elements connected to the ground state 6s. The latter is used for an analysis of the wavelength-dependent light shift in Cs. A range of experimental details is presented, combined with a survey of realistic lasers parameters. These are adopted to project the feasibility of the scheme to eventually be capable of delivering data beyond the standard model of particle physics.

In this paper, we have carried out the calculations of the weighted oscillator strengths and the transition probabilities for a few low-lying transitions of boron-like ions: Mg VIII, Si X and S XII which are astrophysically important, particularly, in the atmospheres of the solar corona. We have employed an all-order relativistic many-body theory called the relativistic coupled-cluster theory to calculate very precisely these atomic quantities of astrophysical interest. We have reported for the first time the transition probabilities for some forbidden transitions which are unavailable in the literature; either theoretically or experimentally. We also discuss the physical effects associated with these transitions. Our data can be used for the identification of spectral lines arising from the coronal atmospheres of Sun and Sun-like stars having an extended corona., 8 pages, 4 tables

We demonstrate the importance of electron correlation effects in the hyperfine structure constants of many low-lying states in $^{210}\mathrm{Fr}$ and $^{212}\mathrm{Fr}$. This is achieved by calculating the magnetic dipole and electric quadrupole hyperfine structure constants using the Dirac-Fock approximation, second-order many-body perturbation theory, and the coupled-cluster method in the singles and doubles approximation in the relativistic framework. By combining our recommended theoretical results with the corresponding experimental values, improved nuclear magnetic dipole and electric quadrupole moments of the above isotopes are determined. In the present work, it is observed that there are large discrepancies between the hyperfine structure constants of the $7{D}_{5/2}$ state obtained from the experimental and theoretical studies, whereas good agreement is found for the other ${D}_{5/2}$ states. Our estimated hyperfine constants for the $8P,\phantom{\rule{0.16em}{0ex}}6D,\phantom{\rule{0.16em}{0ex}}10S$, and $11S$ states could be very useful as benchmarks for the measurement of these quantities.

The connections between the Random Phase Approximation (RPA) and Many-Body Perturbation Theory (MBPT) and its all order generalization, the Coupled-Cluster Theory (CCT), have been explored. Explicit expressions have been derived for the electric dipole amplitudes for allowed and forbidden transitions induced by the parity non-conserving neutral weak interaction. The Goldstone diagrams associated with the RPA terms in both cases are shown to arise in MBPT and CCT, and the numerical verification of this relationship is made for the allowed electric dipole transitions.

Despite the remarkable success of the standard model, it is widely believed that it is just an intermediate step in understanding the properties of the elementary particles in nature and the interactions between them. Studies of parity non-conservation in atomic systems based on non-accelerator methods have advanced over the years and they have now attained the maturity to test the standard model. The most accurate data from this approach comes from the 6s 2 S 1/2 →7s 2 S 1/2 transition in cesium. An experiment on singly ionized barium has been proposed to carry out a further test of this kind independent of cesium. We discuss here the result of our ab initio calculation of the 6s 2 S 1/2 →5d 2 D 3/2 parity non-conserving electric dipole transition amplitude in 137 Ba + based on a novel relativistic coupled-cluster theory. We also discuss a possible improvement of the existing cesium parity non-conservation calculations.

The magnetic dipole and electric quadrupole hyperfine constants of Aluminium (27Al) atom are computed using the relativistic coupled cluster (CC) and unitary coupled cluster (UCC) methods. Effects of electron correlations are investigated using different levels of CC approximations and truncation schemes. The ionization potentials, excitation energies, transition probabilities, oscillator strengths and nuclear quadrupole moment are computed to assess the accuracy of these schemes. The nuclear quadrupole moment obtained from the present CC and UCC calculations in the singles and doubles approximations are 142.5 mbarn and 141.5 mbarn, respectively. The discrepancies between our calculated IPs and EEs and their measured values are better than 0.3%. The other one-electron properties reported here are also in excellent agreement with the measurements.

This review article deals with some case studies of relativistic and correlation effects in atomic systems. After a brief introduction to relativistic many-electron theory, a number of applications ranging from correlation energy to parity non-conservation in atoms are considered. There is a special emphasis on relativistic coupled-cluster theory as most of the results presented here are based on it., Comment: Review article, 4 eps figures, latex 2e

The relativistic coupled cluster theory is employed to calculate electric quadrupole (E2) transition probabilities among the doublet states of Mg II which are of interest in astrophysical problems. This is the first time a highly correlated fully ab initio method has been used to compute these quantities for this particular ion. The line strengths and transition probabilities of a number of different transitions are reported and compared with those available in the literature.

The relativistic coupled cluster theory is employed to calculate the hyperfine structure of the 2S 1/2, 2P 1/2, 2P 3/2, 2D 3/2 and 2D 5/2 states of singly ionized calcium. The importance of correlation effects is highlighted. Our results are compared with other theoretical calculations and experiments.

We study the quasiadiabatic dynamics of a one-dimensional system of ultracold bosonic atoms loaded in an optical superlattice. Focusing on a slow linear variation in time of the superlattice potential, the system is driven from a conventional Mott insulator phase to a superlattice-induced Mott insulator, crossing in between a gapless critical superfluid region. Due to the presence of a gapless region, a number of defects depending on the velocity of the quench appear. Our findings suggest a power-law dependence similar to the Kibble-Zurek mechanism for intermediate values of the quench rate. For the temporal ranges of the quench dynamics that we considered, the scaling of defects depends nontrivially on the width of the superfluid region., 6 Pages, 4 Figures

One of the most successful ab initio, highly correlated all-order many-body methods, the relativistic coupled cluster theory, is employed to calculate excitation energies of the doublet states of Mg+ and allowed transitions among them that are of interest in astrophysical problems. We have also calculated oscillator strength for the 3s-4p doublet transitions, which is improved over the existing results. These transition lines have been sought after in astronomical observations because they represent the best column density identifier in the interstellar medium. Our calculated oscillator strength (9.3 × 10-4) and branching ratio (1.80) of these doublet lines matches well with the recent empirical and semiempirical calculations.

Heavy polar diatomic molecules are the primary tools for searching for the T-violating permanent electric dipole moment of the electron (eEDM). Valence electrons in some molecules experience extremely large effective electric fields due to relativistic interactions. These large effective electric fields are crucial to the success of polar-molecule-based eEDM search experiments. Here we report on the results of relativistic ab initio calculations of the effective electric fields in a series of molecules that are highly sensitive to an eEDM, the mercury monohalides (HgF, HgCl, HgBr,and HgI). We study the influence of the halide anions on effective electric field, and identify HgBr and HgI as interesting candidates for future electric dipole moment search experiments.

The permanent electric dipole moment of the ${X}^{2}{\ensuremath{\Sigma}}^{+}$ electronic ground state of the strontium monofluoride molecule is calculated using a relativistic coupled-cluster method. Our result is compared with those of other calculations and that of experiment. Individual contributions arising from different physical effects are presented. The result obtained suggests that the relativistic coupled-cluster method used in the present work is capable of yielding accurate results for the permanent electric dipole moments of molecules for which relativistic effects cannot be ignored.

We employ four-component spinor relativistic equation-of-motion coupled-cluster (EOMCC) method within the single- and double- excitation approximation to calculate the single ionization potentials (IPs) and double ionization potentials (DIPs) of the He and Be isoelectronic sequences up to Ne. The obtained results are compared with the available results from the National Institute of Standards and Technology (NIST) database to test the performance of the EOMCC method. We also present intermediate results at different level of approximations in the EOMCC framework to gain insight of the effect of electron correlation. Furthermore, we investigate the dependence of the IPs and DIPs of these ions on the ionic charge and observe that these follow parabolic trends. Comparison between the trends of IPs and DIPs in both the classes of considered systems are categorically demonstrated., 8 pages, 3 figures

We report the general implementation of the relativistic equation-of-motion coupled-cluster method to calculate double ionization spectra (DI-EOMCC) of atomic and molecular systems. As a first application, this method is employed to calculate the principal valence double ionization potential values of He and alkaline earth metal (Be, Mg, Ca, Sr and Ba) atoms. Our results are compared with the results available from the national institute of standards and technology (NIST) database and other ab initio calculations. We have achieved an accuracy of ~ 0.1%, which is an improvement over the first principles T-matrix calculations [J. Chem. Phys. 123, 144112 (2005)]. We also present results using the second-order many-body perturbation theory and the random- phase approximation in the equation-of-motion framework and these results are compared with the DI-EOMCC results., Comment: 5 pages, 4 figure

An accurate determination of the effective electric field $({E}_{\mathrm{eff}})$ in YbF is important as it can be combined with the results of future experiments to give an improved new limit for the electric dipole moment of the electron. We report a relativistic coupled-cluster calculation of this quantity in which all the core electrons were excited. It surpasses the approximations made in the previous reported calculations. We obtain a value of 23.1 GV/cm for ${E}_{\mathrm{eff}}$ in YbF with an estimated error of less than 10%. The crucial roles of the basis sets and the core excitations in our paper are discussed.

We report our successful implementation of the relativistic equation-of-motion coupled-cluster (EOMCC) method. This method is employed to compute the principal ionization potentials (IPs) of closed-shell rare-gas atoms, He-like ions, Be-like ions, along with Na${}^{+}$, Al${}^{+}$, K${}^{+}$, Be, and Mg. Four-component Dirac spinors are used in the calculations, and the one- and two-electron integrals are evaluated using the Dirac-Coulomb Hamiltonian. Our results are in excellent agreement with available measurements, which are taken from the National Institute of Science and Technology database. The accuracies of the calculations are estimated to be within one half of a percent for He-like and Be-like ions and 1% for the heavier systems. We also present results using the second-order many-body perturbation theory and random-phase approximation in the EOMCC framework. These results are compared with those of EOMCC at the level of single and double excitations in order to assess the role of the electron correlation effects in the intermediate schemes considered in our calculations.

The parity (P) and time-reversal (T) odd coupling constant associated with the tensor-pseudotensor (T-PT) electron-nucleus interaction and the nuclear Schiff moment (NSM) have been determined by combining the result of the measurement of the electric dipole moment (EDM) of a $^{129}\mathrm{Xe}$ atom and our calculations based on the relativistic-coupled-cluster (RCC) theory. Calculations using various relativistic many-body methods have been performed at different levels of approximation. The accuracies of our results are estimated by comparing our dipole polarizability calculations of the ground state of Xe with its most precise available experimental data, and taking into consideration the difference of the results of our RCC single- and double-excitation calculations with and without the important triple excitations as well as the size of our basis set. The nonlinear terms that arise in the RCC theory were found to be crucial for achieving high accuracy in the calculations. We obtain the upper limits for the T-PT electron-nucleus coupling coefficient and NSM as $1.6\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$ and $1.2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}9}e\phantom{\rule{0.28em}{0ex}}{\text{fm}}^{3}$, respectively, by combining our calculations with the available measurement. Our results, in combination with future EDM measurements in atomic Xe, could improve these limits further.

In this paper we present a new method of generating a relativistic basis set for atomic Dirac–Fock (DF) orbitals. Here, all the occupied and a few low-lying unoccupied DF orbital wavefunctions of atoms obtained from the finite basis set expansion approach are replaced by orbital wavefunctions obtained from numerical solutions. We compare this with the Gaussian basis set generation by employing orbitals obtained from both the approaches in a coupled cluster method and computing the ionization potential and oscillator strengths for Mg + and Ca + using the above two different bases. The new method is found to be more appropriate for high-precision calculations.

The existence of the permanent electric dipole moment (EDM) of an atom implies the simultaneous violation of parity and time-reversal symmetries. Two experiments based on laser cooling have been proposed to search for the EDM of atomic ytterbium. We propose three different relativistic many-body approaches to calculate the EDM of atoms with strongly interacting configurations. Two of them are based on the configuration-interaction method and the third is an algebraic many-body perturbation theory that explicitly uses configuration state functions. We use these three approaches to calculate the EDM of atomic ytterbium arising from an electron-nucleus tensor-pseudotensor interaction. The results of these calculations are in excellent agreement with each other.

We first test our recently developed relativistic coupled-cluster-based linear response theory (RCCLRT) by computing the principal and the shake-up ionization potentials (IP) of highly stripped atoms. Comparison is made between the IP values obtained from the relativistic and non-relativistic CCLRT calculations. The comparisons for light atoms, where the relativistic contributions are negligible, provide a test of the method, while comparisons for heavy atoms quantify the relativistic effect. For one-valence problems such as ionization processes, there is a formal equivalence between the principal IP values from the CCLRT and multi-reference coupled cluster (MRCC) theory when using the 1h-0p model space. The principal IPs obtained from the CCLRT are size-extensive, but the (2h-1p) shake-up IPs are not fully size-extensive, where the size-inextensivity error scales as the number of valence excitations. The computed valence and shake-up ionization energies via the RCCLRT approach are in excellent agreement with experimental data. The IPs computed using the non-relativistic CCLRT also match favourably well with the experiment only when the atomic number and ionic charge are small.

The recent experimental observation of the nuclear anapole moment in atomic caesium has confirmed the existence of the nuclear spin-dependent parity non-conserving nucleus-electron interaction. Atomic ytterbium (Yb) is presently being explored as a possible candidate for detecting the nuclear anapole moment. The result of our relativistic many-body calculations suggest that Yb may indeed be very suitable for this purpose.

We have developed and applied the relativistic coupled-cluster-based linear response theory ~RCCLRT! for computing the principal as well as the shake-up ionization potentials ~IP’s ! of Li, Be, Na, and Mg where the single-particle orbitals are generated by solving the relativistic Hartree-Fock-Roothaan equations using the Gaussian basis functions on a grid. The computed principal and shake-up ionization energies by the RCCLRT approach are in favorable agreement with the experimental results. Since for the ~one-valence! IP problem, there is a formal equivalence between the principal IP values as obtained from the CCLRT and those obtained as eigenvalues of the multireference coupled-cluster theory, the computed quantities are fully size extensive. The approach via the RCCLRT has the additional advantage of providing the shake-up IP’s as well. These are, however, not fully size extensive, but the error scales as the number of valence excitations (2 h-1p), so the inextensivity error is rather small. @S1050-2947~99!01907-1# PACS number~s!: 31.15.Dv

Atomic transition lines of neutral calcium were first found in solar spectrum as early as the middle of the 19th century, when the 4227-A line was identified along with the famous singly ionized H and K lines @1#. Neutral calcium lines have also been observed in all types of stellar and interstellar spectra, such as late-type dwarf stars. The crude abundance of Ca I (l56717.7 A ) has been observed in Am binaries@2#. To confirm those identifications and to find new lines, one has to depend on atomic experimental data or computational data based on theoretical models of the calcium atom. The abundances of neutral calcium in these astronomical bodies depend on the oscillator strengths of those lines, which come from the excitation energies of various levels and transition moments among those levels. The difficulty in accurately estimating transition energies and oscillator strengths of neutral calcium atom arises mainly due to the following reasons: ~a! The precise computation of transition energies and oscillator strengths requires a balanced description of the ground and excited states. ~b! The use of an inadequate basis leads to difficulties in describing the excited states and an unbalanced treatment of dynamical correlation and polarization effects. The problems due to basis set inadequacy can be removed partially by enlarging the basis for small and moderate-sized atomic and molecular systems. Here, the size extensivity @3# of the theory plays an important role in handling the proper treatment of electron correlation, and in that way it properly treats the differential correlation energies of the interacting ~initial and final states! zeroth-order states. It ensures that the state energies scale linearly with the number of electrons in a rigorous way. The accuracy of the computed excitation energy depends mostly upon the quality of the unoccupied valence orbitals in which excitation occurs. The traditional choice of some unoccupied valence orbitals from a ground-state selfconsistent-field ~SCF! computation introduces V N orbitals that are best suited for describing negative ions, and not lowlying excited states. Thus the valence orbitals, those that are not occupied in the ground-state SCF, should be taken as more representative orbitals suitable for excited states. One possible choice emerges from the restricted single excitation configuration interaction procedure@4#, where excitations are only permitted from the highest occupied orbitals. A simpler and often equivalent approaches involves using improved virtual orbitals ~IVO’s !@ 5 #in the H v valence space or reference space. Here the IVO’s are generated by single orbital SCF optimization in which the Fock operator is defined by promoting an electron from the highest occupied orbital to the orbital being optimized, while all the previously determined orbitals are kept frozen. Alternatively this can be accomplished by a unitary transformation @6#. The IVO orbital energies obtained in this way are lower than those evaluated from the traditional SCF procedure due to the absence of an extra Coulomb operator in the former procedure. For example, in a neutral calcium atom H v calculation, the twoorbital (4 s,4p) minimal reference space is produced by the sequence

We present a new hybrid method to solve the relativistic Hartree-Fock-Roothan equations where the one- and two-electron radial integrals are evaluated numerically by defining the basis functions on a grid. This procedure reduces the computational costs in the evaluation of two-electron radial integrals. The orbitals generated by this method are employed to compute the ionization potentials, excitation energies and oscillator strengths of alkali-metal atoms and elements of group IIIA through second order many-body perturbation theor and other correlated theories., RevTex (15 pages) one figure

The general features of parity nonconservation (PNC) in atoms arising from neutral weak currents and the nuclear anapole moment are discussed. The theoretical approaches used to calculate PNC observables are briefly mentioned. A brief review of the present status of atomic PNC is presented and its potential as a probe of physics beyond the standard model is highlighted.

The ab initio effective valence shell Hamiltonian (Hυ) method is used to compute the excitation energies and oscillator strengths for resonance transitions in Mg-like ions, as well as their lowest ionization potentials. The computed excitation energies and oscillator strengths from the Hυ method are in excellent agreement with experiment and with the best values from other high level correlated computations, where available. Several previous discrepancies between theory and experiment are now removed. The present work also investigates the dependence of the calculated Hυ oscillator strengths on the nature and choice of the valence orbitals and provides a comprehensive study of the convergence of Hυ calculations with respect to the enlargement of the valence space.

We obtain the complete quantum phase diagram of bosons on a two-leg ladder in the presence of attractive onsite and repulsive interchain nearest-neighbor interactions by imposing the onsite three-body constraint. We find three distinct phases; namely, the atomic superfluid (ASF), dimer superfluid (DSF), and the dimer rung insulator (DRI). In the absence of the interchain nearest-neighbor repulsion, the system exhibits a transition from the ASF to the DSF phase with increasing onsite attraction. However, the presence of the interchain nearest-neighbor repulsion stabilizes a gapped DRI phase, which is flanked by the DSF phase. We also obtain the phase diagram of the system for different values of the interchain nearest-neighbor interaction. By evaluating different order parameters, we obtain the complete phase diagram and the properties of the phase transitions using the self-consistent cluster mean-field theory., Comment: 9 pages, 15 figures

We employ the closed-shell perturbed relativistic coupled-cluster (RCC) theory developed by us earlier [Phys. Rev. A {\bf 77}, 062516 (2008)] to evaluate the ground state static electric dipole polarizabilities (\alpha s) of several atomic systems. In this work, we have incorporated a class of higher order many-body effects in our calculations that had not been taken into account in the above paper. We highlight their importance in improving the accuracy of $\alpha$. We also calculate the ground state \alpha s of the inert gas atoms and several iso-electronic singly and doubly charged ions in order to make a comparative study of the trends of the correlation effects. Furthermore, we have developed a method to construct intermediate diagrams that are required for the computation of the unperturbed singles and doubles coupled-cluster amplitudes. Our RCC results are compared with those of many-body perturbation theory at different orders to demonstrate the importance of higher order correlation effects for the accurate determination of (\alpha s) of the systems that we have considered., Comment: 11 pages, 15 figures

We investigate electric quadrupole hyperfine-structure constant ($B$) results in ${}^{135}$Ba${}^{+}$ and ${}^{137}$Ba${}^{+}$ and compare their ratios with the reported measurements of the ratio between the nuclear quadrupole moment ($Q$) values of these isotopes. We carry out confidence tests for the reported experimental $B$ values and calculations of $B/Q$ from the present work. Inconsistencies in the experimental $B$ values are observed in both the isotopes from different experiments performed using the same techniques. The present calculations are carried out using an all order relativistic many-body theory considering only single and double excitations in the coupled-cluster ansatz. After a detailed analysis of the results, the values of $Q$ we obtain for ${}^{135}$Ba and ${}^{137}$Ba are 0.153(2)$b$ and 0.236(3)$b$, respectively, which differ by about 4$%$ from the currently referred precise values.

We study a system of hard-core bosons at half-filling in a one-dimensional optical superlattice. The bosons are allowed to hop to nearest and next-nearest neighbor sites producing a zig-zag geometry and we obtain the ground state phase diagram as a function of microscopic parameters using the finite-size density matrix renormalization group (FS-DMRG) method. Depending on the sign of the next-nearest neighbor hopping and the strength of the superlattice potential the system exhibits three different phases, namely the bond-order (BO) solid, the superlattice induced Mott insulator (SLMI) and the superfluid (SF) phase. When the signs of both hopping amplitudes are the same (the "unfrustrated" case), the system undergoes a transition from the SF to the SLMI at a non-zero value of the superlattice potential. On the other hand, when the two amplitudes differ in sign (the "frustrated" case), the SF is unstable to switching on a superlattice potential and also exists only up to a finite value of the next nearest neighbor hopping. This part of the phase diagram is dominated by the BO phase which breaks translation symmetry spontaneously even in the absence of the superlattice potential and can thus be characterized by a bond order parameter. The transition from BO to SLMI appears to be first order., Comment: 6 pages, 11 figures

Three different measurements have been reported for the ground state quadrupole polarizability in the singly ionized barium (Ba$^+$) which disagree with each other. Our calculation of this quantity using the relativistic coupled-cluster method disagrees with two of the experimental values and is within the error bars of the other. We discuss the issues related to the accuracy of our calculations and emphasize the need for further experiments to measure the quadrupole polarizability for this state and/or the 5D states., 6 pages, 3 tables

The Mott insulator-superfluid transition for ultracold bosonic atoms in an optical lattice has been extensively studied in the framework of the Bose-Hubbard model with two-body on-site interactions. In this paper, we analyze the additional effect of the three-body on-site interactions on this phase transition in optical lattice and the transitions between the various phases that arise in an optical superlattice. Using the mean-field theory and the density matrix renormalization group method, we find the phase diagrams depicting the relationships between various physical quantities in an optical lattice and superlattice. We also suggest possible experimental signatures to observe the three-body interactions., Comment: 5 pages, 9 figures Resubmitted after a few changes. http://pra.aps.org/abstract/PRA/v85/i5/e051604 http://pra.aps.org/abstract/PRA/v85/i5/e051604

In this paper we present a variant of Monkhorst's coupled-cluster-based linear-response approach designed for direct calculations of static properties of closed-shell many-fermion systems [Int. J. Quantum Chem Symp. 11, 421 (1977)]. All the required equations are derived in the framework of the coupled-cluster singles and doubles model. Although the approach has been developed with the calculation of electric-dipole moment of atoms and molecules due to parity- and time-reversal-violating interactions in mind, it is general enough to be applicable to other problems which require the presence of two one-electron perturbations.

We propose indium (In) as a possible candidate for observing the permanent electric dipole moment (EDM) arising from the violations of parity (P) and time-reversal (T) symmetries. This atom has been laser cooled and therefore the measurement of its EDM has the potential of improving on the current best EDM limit for a paramagnetic atom which comes from thallium. We report the results of our calculations of the EDM enhancement factor due to the electron EDM and the ratio of the atomic EDM to the electron-nucleus scalar-pseudoscalar (S-PS) interaction coupling constant in In in the framework of the relativistic coupled cluster theory. It might be possible to get new limits for the electron EDM and the S-PS CP violating coupling constant by combining the results of our calculations with the measured value of the EDM of In when it is available. These limits could have important implications for the standard model (SM) of particle physics., 5 pages, 1 fig, Rapid Communication

In this paper we analyze the various phases exhibited by a system of ultracold bosons in a periodic optical superlattice using the mean field decoupling approximation. We investigate for a wide range of commensurate and incommensurate densities. We find the gapless superfluid phase, the gapped Mott insulator phase, and gapped insulator phases with distinct density wave orders., Comment: 6 pages, 7 figures, 4 tables

The electric dipole moment (EDM) enhancement factor of atomic Tl is of considerable interest as it has been used in determining the most accurate intrinsic electron EDM limit to date. However, the value of this quantity varies from $-179$ to $-1041$ in different approximations. In view of the large uncertainties associated with many of these calculations, we have employed the relativistic coupled-cluster theory with single and double excitations and a subset of leading triple excitations and obtained the EDM enhancement factor of Tl as $-466$, which in combination with the most accurate measured value of Tl EDM yields $2.0 \times 10^{-27}\,{\mathrm e\,cm}$ as the new upper limit for the EDM of the electron. The importance of all-order correlation effects is emphasized and their trends are compared with those of two other ab initio calculations., Comment: 4 pages, 4 tables, 2 figures

We report the implementation of a general-order relativistic coupled-cluster method for performing high-precision calculations of atomic and molecular properties. As a first application, the black-body radiation shift of the Al${}^{+}$ clock has been estimated precisely. The computed shift relative to the frequency of the $3{s}^{2} {}^{1}{S}_{0}^{e}\ensuremath{\rightarrow}3s3p {}^{3}{P}_{0}^{o}$ clock transition given by $(\ensuremath{-}3.66\ifmmode\pm\else\textpm\fi{}0.60)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}18}$ calls for an improvement over the recent measurement with a reported result of $(\ensuremath{-}9\ifmmode\pm\else\textpm\fi{}3)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}18}$ [Phys. Rev. Lett. 104, 070802 (2010)].

We analyze various quantum phases of ultracold bosonic atoms in a periodic one dimensional optical superlattice. Our studies have been performed using the finite size density matrix renormalization group (FS-DMRG) method in the framework of the Bose-Hubbard model. Calculations have been carried out for a wide range of densities and the energy shifts due to the superlattice potential. At commensurate fillings, we find the Mott insulator and the superfluid phases as well as Mott insulators induced by the superlattice. At a particular incommensurate density, the system is found to be in the superfluid phase coexisting with density oscillations for a certain range of parameters of the system., 7 pages, 11 figures