Utilizing the tools of quantum optics to prepare and manipulate quantum states of motion of a mechanical resonator is currently one of the most promising routes to explore non-classicality at a macroscopic scale. An important quantum optomechanical tool yet to be experimentally demonstrated is the ability to perform complete quantum state reconstruction. Here, after providing a brief introduction to quantum states in phase space, the current proposals for state reconstruction of mechanical motional states are reviewed and contrasted and experimental progress is discussed. Furthermore, it is shown that mechanical quadrature tomography using back-action-evading interactions gives an *s*-parameterized Wigner function where the numerical parameter *s* is directly related to the optomechanical measurement strength. The effects of classical noise in the optical probe for both state reconstruction and state preparation by measurement are also discussed.

In this article a particular solution of Heun equation is derived by making use of the Nikiforov-Uvarov (NU) method which provides exact solutions for general hypergeometric equation and eigenvalues together with eigenfunctions of the Heun equation for this particular solution are obtained. One to one correspondence (isomorphism) of the aforesaid equation with the radial Schrödinger equation is emphasized and also physical counterparts of the parameters in this equation are put forward by introducing solutions for two different potential functions (Hulthen and Woods-Saxon potentials).

]]>Very recently, the 4-8 line defects (LDs), containing homoelemental B-B and N-N bonds at the squares and octagons, have been observed in BN sheets under electron-beam irradiation. Inspired by the experiment, a first-principles study on these 4-8 LD-embedded BN sheets and the doping effects of transition metal (TM) atoms was conducted. It was found that the homoelemental bonds induce defect states in the band gap of BN sheets, which markedly reduce the gap value by 38%. The line defect binds the foreign TM atoms strongly, which can form one-dimensional TM chains in the sheets. Consequently, diverse electronic and magnetic properties are induced into BN sheets: the Cr- and Ni-chain dopings bring a quasi-spin-gapless semiconducting feature, the Fe- and Co-chain dopings cause a ferromagnetic semiconducting behavior, and the Mn one even transforms the sheets into antiferromagnetic semiconductors. The studies demonstrate that these TM-chain-doped BN sheets are potential candidates for spintronics and nanodevices.

]]>A protocol able to prepare two remote and initially uncorrelated microwave modes in an entangled stationary state, which is certifiable using only local optical homodyne measurements id proposed. The protocol is an extension of continuous variable entanglement swapping, and exploits two hybrid quadripartite opto-electro-mechanical systems in which a nanomechanical resonator acts as a quantum interface able to entangle optical and microwave fields. The proposed protocol allows to circumvent the problems associated with the fragility of microwave photons with respect to thermal noise and may represent a fundamental tool for the realization of quantum networks connecting distant solid-state and superconducting qubits, which are typically manipulated with microwave fields. The certifying measurements on the optical modes guarantee the success of entanglement swapping without the need of performing explicit measurements on the distant microwave fields.

]]>Spin-orbit splitting in transition-metal dichalcogenide monolayers is investigated on the basis of density-functional theory within explicit two-dimensional periodic boundary conditions. The spin-orbit splitting reaches few hundred meV and increases with the size of the metal and chalcogen atoms, resulting in nearly 500 meV for WTe_{2}. Furthermore, we find that similar to the band gap, spin-orbit splitting changes drastically under tensile strain. In centrosymmetric transition metal dichalcogenide bilayers, spin-orbit splitting is suppressed by the inversion symmetry. However, it could be induced if the inversion symmetry is explicitly broken, e.g. by a potential gradient normal to the plane, as it is present in heterobilayers (Rashba-splitting). In such systems, the spin-orbit splitting could be as large as for the heavier monolayer that forms heterobilayer. These properties of transition metal dichalcogenide materials suggest them for potential applications in opto-, spin- and straintronics.

A theoretical analysis of the resonance fluorescence of a two-level atom in a classical monochromatic field with feedback phase switching depending on the fluorescence triplet component which the last spontaneously emitted photon belongs to is presented. The considered feedback loop is a hybrid quantum-classical system. Statistics of photoemissions into the triplet components is investigated as well as correlations between the components. In contrast to the well-known resonance fluorescence of a two-level atom without feedback phase switching, a bunching of photocounts is predicted in each side-band, and successive photoemissions into different side-bands manifest antibunching. The type of the statistics can efficiently be controlled by the frequency detuning of the external field. In many points the considered feedback scheme provides drastically different statistical features of fluorescence when compared with the scheme of frequency-unselective feedback phase switching.

]]>The problem of the stability of a cavity optomechanical system based on an oscillator having at the same time low optical and mechanical losses is addressed. As it is the aim to extend the use of optical squeezing as a tool for improving quantum limited displacement sensing at low frequency, a family of opto-mechanical devices designed to work at frequencies of about 100 kHz was developed . The devices actually meet the initial design goals, but new requirements have emerged from the analysis of their behavior in optical cavities, due to the interaction between the cavity locking system and the low order normal modes of the devices.

]]>The four-site Hubbard model is considered from the exact diagonalisation and variational method points of view. It is shown that the exact ground-state can be recovered by a symmetry projected Slater determinant, irrespective of the interaction strength. This is in contrast to the Gutzwiller wave-function, which is calculated as well.

]]>Synchronization of two dissipatively coupled Van der Pol oscillators in the quantum regime is studied. Due to quantum noise strict frequency locking is absent and is replaced by a crossover from weak to strong frequency entrainment. The differences to the behavior of one quantum Van der Pol oscillator subject to an external drive are discussed. Moreover, a possible experimental realization of two coupled quantum Van der Pol oscillators in an optomechanical setting is described.

]]>Monolayer transition metal dichalcogenides are promising materials for photoelectronic devices. Among them, molybdenum disulphide (MoS_{2}) and tungsten disulphide (WS_{2}) are some of the best candidates due to their favorable band gap values and band edge alignments. Here, various perturbative corrections to the DFT electronic structure, e.g. GW, spin-orbit coupling, as well as many-body excitonic and trionic effects are considered, and accurate band gaps as a function of homogeneous biaxial strain in these materials are calculated. All of these corrections are shown to be of comparable magnitudes and need to be included in order to obtain an accurate electronic structure. The strain at which the direct-to-indirect gap transition occurs is calculated. After considering all contributions, the direct to indirect gap transition strain is predicted to be at 2.7% in MoS_{2} and 3.9% in WS_{2}. These values are generally higher than the previously reported theoretical values.

A possible scenario of the Lorentz symmetry violation is discussed based on the arising of geometric quantum phases yielded by the effects of the Lorentz symmetry violation in the CPT-even gauge sector of Standard Model Extension. Analogues of the Anandan quantum phase and the scalar Aharonov-Bohm effect for a neutral particle [J. Anandan, Phys. Lett. A **138**, 347 (1989)] are obtained from the parity-odd sector of the tensor . Moreover, we build quantum holonomies associated with the analogue of the Anandan quantum phase and discuss a possible analogy with the geometric quantum computation [A. Ekert *et al*., J. Mod. Opt. **47**, 2501 (2000)].

Quantum states encoded in microwave photons or qubits can be effectively manipulated, whereas optical photons can be coherently transferred via optical fibre and waveguide. The reversible conversion of quantum states between microwave and optical photons will hence enable the distribution of quantum information over long distance and significantly improve the scalability of hybrid quantum systems. Owning to technological advances, mechanical resonators couple to quantum devices in distinctly different spectral range with tunable coupling, and can serve as a powerful interface to connect those devices. In this review, recent theory and experimental progress in the coherent conversion between microwave and optical fields via optoelectromechanical transducers are summarized. The challenges and perspectives in achieving single-photon-level quantum state conversion are also discussed.

]]>The opening of a gap in single-layer graphene is often ascribed to the breaking of the equivalence between the two carbon sublattices. It is shown by angle-resolved photoemission spectroscopy that Ir- and Na-modified graphene grown on the Ir(111) surface presents a very large unconventional gap that can be described in terms of a phenomenological massless Dirac model. The consequences and differences of this model are discussed in comparison of the standard massive gap model, and the conditions under which such anomalous gap can arise from a spontaneous symmetry breaking are investigated.

]]>In this paper it is demonstrated that the precise physical nature of the Dember effect is a concentration gradient of nonequilibrium carriers under nonuniform illumination. We used the fact that any photo-EMF (electromotive force) can only exist in the presence of nonequilibrium charge carriers, when there are two different Fermi quasilevels. That is why the Dember EMF (as the photo-EMF of any nature ) is not identified as a voltage drop arising between the device contacts in open circuit. Moreover, a correct definition of the EMF is only possible if the problem is solved in a closed circuit. It is shown that the Dember EMF does not depend on the difference of electron-to-hole diffusion coefficients and it is not linked to ambipolar diffusion. Additionally, it is found that the sign of the EMF depends on the ratio between the recombination rates on the contacts, which can be detected from the spectral characteristic of the Dember EMF.

]]>The phonon dispersion of singly oriented graphene on Ir(111) has been determined by angle-resolved inelastic electron scattering. Replica of graphene phonon bands are induced by the moiré superstructure. Calculations for a linear chain of C atoms attached to an infinitely heavy substrate reveal that imposing a superstructure by periodically varying the C–C interaction and the C–substrate coupling induces replicated phonons at wave vectors reflecting the supercell periodicity. Deviations between the phonon dispersion of graphene on Ir(111) and of pristine graphene are analyzed and rationalized in terms of the weak graphene–Ir(111) interaction.

]]>We use a functional renormalization group approach to study the instabilities due to electron-electron interactions in a bilayer honeycomb lattice model with AA stacking, as it might be relevant for layered graphene with this structure. Starting with a tight-binding description for the four π-bands, we integrate out the modes of the dispersion by successively lowering an infrared cutoff and determine the leading tendencies in the effective interactions. The antiferromagnetic spin-density wave is an expected instability for dominant local repulsion among the electrons, but for nonlocal interaction terms also other instabilities occur. We discuss the phase diagrams depending on the model parameters. We compare our results to single-layer graphene and the more common AB-stacked bilayer, both qualitatively and quantitatively.

]]>In the paper, for the Kerr field, we prove that Chandrasekhar's Dirac Hamiltonian and the self-adjoint Hamiltonian with a flat scalar product of the wave functions are physically equivalent. Operators of transformation of Chandrasekhar's Hamiltonian and wave functions to the η representation with a flat scalar product are defined explicitly. If the domain of the wave functions of Dirac's equation in the Kerr field is bounded by two-dimensional surfaces of revolution around the *z* axis, Chandrasekhar's Hamiltonian and the self-adjoint Hamiltonian in the η representation are Hermitian with equality of the scalar products, .

Many experiments have revealed that the surfaces of graphene and graphene-like structures can play an active role as a host surface for clusterization of transition metal atoms. Motivated by these observations, we investigate theoretically the adsorption, diffusion and magnetic properties of Pt clusters on three different two-dimensional atomic crystals using first principles density functional theory. We found that monolayers of graphene, molybdenum disulfide (1H-MoS_{2}) and tantalum disulfide (1T-TaS_{2}) provide different nucleation characteristics for Pt cluster formation. At low temperatures, while the bridge site is the most favorable site where the growth of a Pt cluster starts on graphene, top-Mo and top-Ta sites are preferred on 1H-MoS_{2} and 1T-TaS_{2}, respectively. Ground state structures and magnetic properties of Pt_{n} clusters ( 2,3,4) on three different monolayer crystal structures are obtained. We found that the formation of Pt_{2} dimer and a triangle-shaped Pt_{3} cluster perpendicular to the surface are favored over the three different surfaces. While bent rhombus shaped Pt_{4} is formed on graphene, the formation of tetrahedral shaped clusters are more favorable on 1H-MoS_{2} and 1T-TaS_{2}. Our study of the formation of Pt_{n} clusters on three different monolayers provides a gateway for further exploration of nanocluster formations on various surfaces.

This erratum refers to the article above, first published online on 31 December 2012 and later in print in Annalen der Physik, 525(1–2), 66–73 (2013).

]]>The accelerated expansion of the Universe is now a firmly established observational fact. In recent times, significant progress has been made in measuring the cosmic expansion history and the growth of structures in the Universe with the aim to constrain dark energy models.

This issue reviews the state of the art of observational constraints on models of cosmic acceleration and recent progress, and discusses prospects of understanding more about the nature of dark energy. Picture: SKA Organisation/Swinburne Astronomy Productions

]]>The accelerated expansion of the Universe is now a firmly established observational fact. In recent times, significant progress has been made in measuring the cosmic expansion history and the growth of structures in the Universe with the aim to constrain dark energy models.This issue reviews the state of the art of observational constraints on models of cosmic acceleration and recent progress, and discusses prospects of understanding more about the nature of dark energy. Picture: SKA Organisation/Swinburne Astronomy Productions
Issue Information: Ann. Phys. 7-8'2014 http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fandp.201470071Issue Information: Ann. Phys. 7-8'2014 2014-08-07T15:19:59.834385-05:00 doi:10.1002/andp.201470071 John Wiley & Sons, Inc. 10.1002/andp.201470071 http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fandp.201470071 Issue Information NA NA Call For Papers: Ann. Phys. 7-8'2014 http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fandp.201470072Call For Papers: Ann. Phys. 7-8'2014 2014-08-07T15:19:55.404521-05:00 doi:10.1002/andp.201470072 John Wiley & Sons, Inc. 10.1002/andp.201470072 http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fandp.201470072 Call for Papers A355 A55 Contents: Ann. Phys. 7-8'2014 http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fandp.201470073Contents: Ann. Phys. 7-8'2014 2014-08-07T15:19:51.998226-05:00 doi:10.1002/andp.201470073 John Wiley & Sons, Inc. 10.1002/andp.201470073 http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fandp.201470073 Contents A56 A58 RETROSPECT – Highlights from recent Annalen der Physik issues http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fandp.201470074RETROSPECT – Highlights from recent Annalen der Physik issues 2014-08-07T15:19:52.16798-05:00 doi:10.1002/andp.201470074 John Wiley & Sons, Inc. 10.1002/andp.201470074 http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fandp.201470074 Retrospect A59 A59 Advisory Board http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fandp.201470075Advisory Board 2014-08-07T15:19:59.873509-05:00 doi:10.1002/andp.201470075 John Wiley & Sons, Inc. 10.1002/andp.201470075 http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fandp.201470075 Advisory Board A60 A60 The Dark Universe – A mystery of 21st century physics http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fandp.201470076The Dark Universe – A mystery of 21st century physics Richard A. Battye, Ariel Goobar, Jochen Weller 2014-08-07T15:19:52.226836-05:00 doi:10.1002/andp.201470076 John Wiley & Sons, Inc. 10.1002/andp.201470076 http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fandp.201470076 EDITORIAL A61 A63 Special Features http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fandp.201470077Special Features 2014-08-07T15:19:52.400034-05:00 doi:10.1002/andp.201470077 John Wiley & Sons, Inc. 10.1002/andp.201470077 http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fandp.201470077 Special Features A64 A64 Fraunhofer and his spectral lines http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fandp.201400807Fraunhofer and his spectral lines Myles W. Jackson 2014-08-07T15:19:52.574179-05:00 doi:10.1002/andp.201400807 John Wiley & Sons, Inc. 10.1002/andp.201400807 http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fandp.201400807 THEN & NOW A65 A69 Constraining chameleon models with cosmology http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fandp.201400058Constraining chameleon models with cosmology Lucas Lombriser 2014-06-16T00:50:42.377054-05:00 doi:10.1002/andp.201400058 John Wiley & Sons, Inc. 10.1002/andp.201400058 http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fandp.201400058 Review Article 259 282

]]>Chameleon fields may modify gravity on cluster scales while recovering general relativity locally. This article reviews signatures of chameleon modifications in the nonlinear cosmological structure, comparing different techniques to model them, summarising the current state of observational constraints, and concluding with an outlook on prospective constraints from future observations and applications of the analytic tools developed in the process to more general scalar-tensor theories. Particular focus is given to the Hu-Sawicki and designer models of gravity.

Galaxy redshift surveys using optical telescopes have, in combination with other cosmological probes, enabled precision measurements of the nature of dark energy. It is shown that radio telescopes are rapidly becoming competitive with optical facilities in spectroscopic surveys of large numbers of galaxies. Two breakthroughs are driving this change. Firstly, individual radio telescopes are more efficient at mapping the sky thanks to the large field-of-view of new phased-array feeds. Secondly, ever more dishes can be correlated in a cost-effective manner with rapid increases in computing power. The next decade will see the coming of age of the radio wavelength as a cosmological probe as first the Pathfinders then, ultimately, the Square Kilometre Array is constructed. The latter will determine precise 3D positions for a billion galaxies, mapping the distribution of matter in the Universe over the last 12 billion years. This radio telescope will be able to constrain the equation of state of dark energy, and its potential evolution, to a precision rivalling that of future optical facilities such as DESI and Euclid.

]]>Recent high-resolution simulations that include Cold Dark Matter (CDM) and baryons have shown that baryonic physics can dramatically alter the dark matter structure of galaxies. These results modify our predictions for observed galaxy evolution and structure. Given these updated expectations, it is timely to re-examine observational constraints on the dark matter model. A few observations exist that may indirectly trace dark matter, and may help confirm or deny possible dark matter models. Warm Dark Matter (WDM) and Self-Interacting Dark Matter (SIDM) are currently the favorite alternative models to CDM. Constraints on the WDM particle mass require it to be so heavy that WDM is nearly indistinguishable from CDM. The best observational test of SIDM is likely to be in the dark matter distribution of faint dwarf galaxies, but there is a lack of theoretical predictions for galaxy structure in SIDM that account for the role of baryons.

]]>In the context of gravity, dark energy is a geometrical fluid with negative equation of state. Since the function is not known *a priori*, the need of a model independent reconstruction of its shape represents a relevant technique to determine which model is really favored with respect to others. To this aim, cosmography is related to a generic and its derivatives in order to provide a model-independent investigation at redshift . The analysis is based on the use of three different cosmological distance definitions, in order to alleviate the duality problem, i.e. the problem of which cosmological distance to use with specific cosmic data sets. We therefore consider the luminosity, , flux, , and angular, , distances and we find numerical constraints by the Union 2.1 supernovae compilation and measurement of baryonic acoustic oscillations, at . We notice that all distances reduce to the same expression, i.e. , at first order. Thus, to fix the cosmographic series of observables, we impose the initial value of *H*_{0} by fitting through supernovae only, in the redshift regime . We find that the pressure of curvature dark energy fluid is slightly lower than the one related to the cosmological constant. This indicates that a possible evolving curvature dark energy realistically fills the current universe. Moreover, the combined use of and shows that the sign of the acceleration parameter agrees with theoretical bounds, while its variation, namely the jerk parameter, is compatible with . Finally, we infer the functional form of by means of a truncated polynomial approximation, in terms of fourth order scale factor .

A new class of “dark energy” models is reviewed and developed, in which the relativistic theory of solids is used to construct material models of dark energy. These are models which include the effects of a continuous medium with well defined physical properties at the level of linearized perturbations. The formalism is constructed for a medium with arbitrary symmetry, and then specialised to isotropic media (which will be the case of interest for the majority of cosmological applications). The theory of relativistic isotropic viscoelastic media is developed whilst keeping in mind that we ultimately want to observationally constrain the allowed properties of the material model. This is done by obtaining the viscoelastic equations of state for perturbations (the entropy and anisotropic stress), as well as identifying the consistent corner of the theory which has constant equation of state parameter . A connection to the non-relativistic theory of solids is obtained by identifying the two quadratic invariants that are needed to construct the energy-momentum tensor, namely the Rayleigh dissipation function and Lagrangian for perturbations. Finally, the notion is developed that the viscoelastic behavior of the medium can be thought of as a non-minimally coupled massive gravity theory. This also provides a tool-kit for constructing consistent generalizations of coupled dark energy theories.

]]>Despite they are not standard candles, the investigation of Gamma–Ray Bursts (GRBs) as a tool for measuring the geometry and expansion rate of the Universe is strongly motivated by their unique combination of huge luminosity, up to more than 10^{53} erg/s, with a redshift distribution extending up to more than *z* = 8. In the recent years, several attempts to exploit the correlation between the photon energy at which the spectrum peaks (“peak energy”) and the “intensity” (radiated energy or luminosity) for “standardizing” GRBs and using them to estimate cosmological parameters have been made. These studies show that already with the present data–set GRBs can provide a significant and independent estimate of Ω_{M} = 0.29 for a flat ΛCDM universe and that the measurements expected from present and next GRB experiments (e.g. *Swift*, *Fermi*/GBM, SVOM, UFFO) will allow us to get clues on dark energy properties and evolution. Under this respect, the study of GRBs will contribute significantly to some of the SKA main science goals, through the characterization by SKA of their radio emission with unprecedented sensitivity and by using the results of GRB measurements at other wavelengths to complement SKA key science project observations of other astrophysical sources.