[en] We demonstrate a simple way to realize control of population transfer and creation of two orthogonal maximally superposition states in a Λ-type four-level system with closely spaced doublet target states via a pair of pump and chirped Stokes pulses. It is illustrated that the population in the initial state can be selectively, completely and robustly transferred to either of the doublet target states via chirped adiabatic passage with the suitable chirp rate and frequency detuning of the Stokes pulse. Besides, creation of two orthogonal maximally superposition states between the initial state and intermediate state with equal amplitude but inverse relative phases is also shown, which may have potential applications in the preparations of quantum bits. (letter)

[en] Our previous paper, part I of the same study, shows the different experimental spectra used to draw a conclusion on the genuine existence of narrow, weakly excited mesonic structures having masses below and a little above the pion (M = 139.56 MeV) mass. This study [1] was instigated by the observation, in the Σ⁺ disintegration—Σ⁺ → pP⁰, P⁰ → μ^-μ⁺ [2]—of a narrow range of dimuon masses. The authors make a conclusion on the existence of a neutral intermediate state P₀ with a mass M = (214.3 ± 0.5) MeV. We present here some attempts to understand the possible nature of the structures observed in part I.

[en] We study the phase-dependent propagation of a strong, resonant pump and two weak symmetrically detuned fields in a two-level system with population decay through a cascade of intermediate levels. As this system forms a closed loop, the propagation is phase-dependent. For an initial total phase Φ=0, there is constructive interference between the two weak fields, leading to parametric amplification on propagation. When Φ=π, destructive interference occurs, leading to absorption of the weak fields on propagation. When the weak fields are initially equal in intensity, and Φ=0,π, Φ remains constant on propagation. For other initial phases, Φ changes on propagation. Dramatic phase changes from π to 0 can occur when the weak fields are initially unequal in intensity and Φ=π.

[en] The dynamical behaviour of crystalline macromolecules and their surrounding solvent as a function of cryo-temperature is reviewed. X-ray crystallography provides structural details of biological macromolecules. Whereas routine data are collected close to 100 K in order to mitigate radiation damage, more exotic temperature-controlled experiments in a broader temperature range from 15 K to room temperature can provide both dynamical and structural insights. Here, the dynamical behaviour of crystalline macromolecules and their surrounding solvent as a function of cryo-temperature is reviewed. Experimental strategies of kinetic crystallography are discussed that have allowed the generation and trapping of macromolecular intermediate states by combining reaction initiation in the crystalline state with appropriate temperature profiles. A particular focus is on recruiting X-ray-induced changes for reaction initiation, thus unveiling useful aspects of radiation damage, which otherwise has to be minimized in macromolecular crystallography

[en] We present a highly efficient scheme for perfect joint remote preparation of an arbitrary $2^n$-qubit W state with minimum quantum resource. Both the senders Alice and Bob intend to jointly prepare one $2^n$-qubit W state for the remote receiver Charlie. In the beginning, they help the remote receiver Charlie to construct one n-qubit intermediate state which is closely related to the target $2^n$-qubit W state. Afterward, Charlie introduces auxiliary qubits and applies appropriate operations to obtain the target $2^n$-qubit W state. Compared with previous schemes, our scheme requires minimum quantum resource and least amount of classical communication. Moreover, our scheme has a significant potential for being adapted to remote state preparation of other special states.

[en] This paper addresses the problem of two-photon double ionization (TPDI) of He(1s²) and He(1s2s¹S). First, we reconsider TPDI of He(1s²) with a photon energy of 2.1 a.u.; it is well known that TPDI is mainly a sequential process, resulting in an electron spectrum dominated by two peaks. In the past, we have noticed that the peaks are shifted as the pulse duration shortens; they move toward each other. The first objective of the present work is to clarify the origin of the shift and to evaluate it quantitatively. In parallel with the resolution of the time-dependent Schroedinger equation (TDSE), we have developed a model calculation based on lowest-order perturbation theory for the laser-atom interaction and for the atomic structure representation. The model agrees with TDSE calculations, and it also explains the physical origin of the shifts. Furthermore, it provides a quantitative evaluation of these shifts. The second objective of the present work is to extend our study to TPDI of He(1s2s¹S), which has received much less attention until now. We have investigated the cases of photon energies of 1.8 and 2.5 a.u. We show that TPDI is dominated by a sequential process where the first ionization leaves a remaining He⁺(2s) ion, which is ionized by a second photon. As in the case of He(1s²), the model agrees with TDSE calculations, and it leads to better insights into the physics underlying the double-ionization process. (authors)

[en] We construct the general formula of one-loop amplitude at four-point vertices using Ossola, Papadopoulos, and Pittau (OPP) method. The incoming and outgoing particles are defined as arbitrary massless particles, and the intermediate state contains arbitrary particles inside. In this works, the amplitude is reconstructed via finding four-type rational coefficients. First, box coefficient is extracted using the four-cut technique with linear algebra. We found that triangle and bubble coefficients can be extracted using three-cut and two-cut technique with Cauchy residue theorem instead of with discrete Fourier sum like the original version of the OPP. Tadpole coefficient can be dropped out, because its scalar integral, which contains only UV divergence, is completely absorbed by renormalization. (paper)

[en] Protein beta-2-microglobulin (β2m) is classically considered the causative agent of dialysis related amyloidosis, a conformational disorder that affects patients undergoing long-term hemodialysis. The wild type (WT) form, the ΔN6 structural variant, and the D76N mutant have been extensively used as model systems of β2m aggregation. In all of them, the native structure is stabilized by a disulfide bridge between the sulphur atoms of the cysteine residues 25 (at B strand) and 80 (at F strand), which has been considered fundamental in β2m fibrillogenesis. Here, we use extensive discrete molecular dynamics simulations of a full atomistic structure-based model to explore the role of this disulfide bridge as a modulator of the folding space of β2m. In particular, by considering different models for the disulfide bridge, we explore the thermodynamics of the folding transition, and the formation of intermediate states that may have the potential to trigger the aggregation cascade. Our results show that the dissulfide bridge affects folding transition and folding thermodynamics of the considered model systems, although to different extents. In particular, when the interaction between the sulphur atoms is stabilized relative to the other intramolecular interactions, or even locked (i.e. permanently established), the WT form populates an intermediate state featuring a well preserved core and two unstructured termini, which was previously detected only for the D76N mutant. The formation of this intermediate state may have important implications in our understanding of β2m fibrillogenesis. (paper)

[en] In this paper, we report polyamorphic transformations of H₂O under isothermal compression and decompression at 150 K, observed by in situ x-ray diffraction. Detailed structural information across the transformations among low-, high-, and very high-density amorphs (LDA, HDA, VHDA) reveals the mechanisms, the reversibility, and (dis)continuity of the transformations. During isothermal (de)compression, the polyamorphic transformations are characterized by a sharp and reversible LDA-VHDA transformation, with an HDA-like form (referred to as HDA’) appearing as an intermediate state. The LDA-VHDA transformation is found to occur in two steps: a discontinuous transition between LDA and HDA’ and a continuous change within HDA’ involving structural reconfigurations and finally converging to VHDA. Both LDA and VHDA are found to be structurally stable showing elastic behavior under (de)compression, while HDA’ is structurally unstable. Lastly, possible relations of these observations to low- and high-density liquids are discussed.

[en] The domain formation induced by perpendicular spin injection has been studied with the magnetic nanopillar structure. When the bottom layer is an unpatterned thin film, an intermediate state is observed and characterized to be a domain formed in the bottom layer. Domain formation is also investigated when the size of the top nanomagnet is increased