AAPPS Bulletin最新文献

Non-Hermitian quantum systems exhibit many novel physical properties of quantum states. We consider a non-Hermtian graphene model based on the tight-binding approximation with the coupling of the graphene and the substrate. We analyze the complex energy structure of this model and its exceptional points as well as relevant topological invariants. We give the analytic complex Berry connection and Berry curvature in the Brillouin zone and investigate numerically the relationships between the complex Berry curvature and the complex energy band structures. We find that the behaviors of the complex Berry curvature depend on the complex energy band structures. The occurrence of the peaks of both real and imaginary parts of the complex Berry curvature corresponds to the exceptional (gapless) points in the Brillouin zone. In particular, the Dirac cone of the imaginary part of the Berry curvature occurs and corresponding to the occurrence of the flat real energy band for the non-Hermitian parameter (eta =3). These results provide some novel insights to the relationship between the non-Hermitian graphene, geometry, and topological invariants.

We briefly review the recent progress of theories and experiments on spin-orbital-angular-momentum (SOAM)-coupled quantum gases. The coupling between the intrinsic degree of freedom of particles and their external orbital motions widely exists in the universe and leads to a broad variety of fundamental phenomena in both classical physics and quantum mechanics. The recent realization of synthetic SOAM coupling in cold atoms has attracted a great deal of attention and stimulated a large amount of considerations on exotic quantum phases in both Bose and Fermi gases. In this review, we present a basic idea of engineering SOAM coupling in neutral atoms, starting from a semiclassical description of atom-light interaction. Unique features of single-particle physics in the presence of SOAM coupling are discussed. The intriguing ground-state quantum phases of weakly interacting Bose gases are introduced, with emphasis on a so-called angular stripe phase, which has not yet been observed at present. It is demonstrated how to generate a stable giant vortex in a SOAM-coupled Fermi superfluid. We also discuss the topological characters of a Fermi superfluid in the presence of SOAM coupling. We then introduce the experimental achievement of SOAM coupling in (^{87})Rb Bose gases and its first observation of phase transitions. The most recent development of SOAM-coupled Bose gases in experiments is also summarized. Regarding the controllability of ultracold quantum gases, it opens a new era, from the quantum simulation point of view, to study the fundamental physics resulting from SOAM coupling as well as newly emergent quantum phases.

In this work, we study the (Dbar{D}), DD, (Dbar{D}_s), (DD_s), (D_sbar{D}_s) and (D_sD_s) tetraquark molecular states with the (J^{PC}=0^{++}) via the QCD sum rules. The prediction (M_{D_sbar{D}_s} = 3.98pm 0.10, text {GeV}) is in very good agreement with the experimental value (M_{X(3960)} = 3956 pm 5pm 10 ,text {MeV}) from the LHCb collaboration and supports assigning the X(3960) as the (D_s^+D_s^-) molecular state with the (J^{PC}=0^{++}). We take account of our previous works on the four-quark states consisting of two color-neutral clusters and acquire the mass spectrum of the ground state hidden-charm and doubly-charm tetraquark molecular states.

Optical microcavities have emerged as promising platforms for ultrasound detection. One of the main tendencies in recent studies is to develop high-Q microresonators for ultrasensitive ultrasound detection, while the nonlinear optical effects become significant but are generally neglected. Here, we propose a thermal-assisted microcavity Raman laser for ultrasound detection. Acoustic waves modulate the resonant frequency of the cavity mode, altering the coupled efficiency of a fixed-wavelength input laser, and therefore the output Raman power. Experimentally, the noise equivalent pressure reaches as low as 8.1 Pa at 120 kHz in air. Besides, it is found that the thermal effect involved in high-Q microcavities can compensate for the low-frequency noises, while without degrading their sensitivity to high-frequency acoustic waves above hundreds of kilohertz. Therefore, it enables long-standing stability during the measurements due to the natural resistance to laser frequency drifts and environmental disturbances, which holds great potential in practical applications of ultrasound sensing and imaging.

Boron neutron capture therapy (BNCT) has been attracting interest as a new radiation modality for cancer therapy because it can selectively destroy cancer cells while maintaining the healthy state of surrounding normal cells. Many experimental trials have demonstrated significant BNCT treatment efficacy using neutron beams from research reactors. However, nuclear reactor technology cannot be scaled to sites in hospitals delivering patient treatment. Therefore, compact accelerator-based neutron sources that could be installed in many hospitals are under development or have even been commissioned at many facilities around the world. In Korea, a radio-frequency (RF) linac-based BNCT (A-BNCT) facility is under development by DawonMedax (DM). It provides the highly efficient production of an epithermal neutron beam with an optimized neutron energy spectrum range of 0.1~10 keV. With a 2-mA 10-MeV proton beam from the accelerator, the irradiation port epithermal neutron flux is higher than 1 × 10⁹ n/cm²⋅s. Comprehensive verification and validation of the system have been conducted with the measurement of both proton and neutron beam characteristics. Significant therapeutic effects from BNCT have been confirmed by DM in both in vitro and in vivo non-clinical trials. Further, during exposure to epithermal neutrons, all other unintended radiation is controlled to levels meeting International Atomic Energy Agency (IAEA) recommendations. Recently, the Korean FDA has accepted an investigational new drug (IND) and the first-in-human clinical trial of BNCT is now being prepared. This paper introduces the principles of BNCT and accelerator-based neutron sources for BNCT and reports the recent advances of DM A-BNCT facility which is the main part of this paper.

We investigate the asymmetric Gaussian steering with the nondegenerate parametric amplifier in a three-mode optomechanical system composed of two optical cavities and a mechanical oscillator. In the presence of the nondegenerate parametric amplifier, we find that the Gaussian steering between the auxiliary cavity and the mechanical resonator without direct interaction is significantly enhanced. By cooling the delocalized Bogoliubov modes over the auxiliary cavity and the mechanical oscillator, the optimal optomechanical entanglement and Gaussian steering can be realized and enhanced. Furthermore, we observe a wider range of parameters for the Gaussian steering with the case of cooling double delocalized modes. In addition, the magnitudes of the asymmetric Gaussian steering in two different directions can be adjusted by altering the decay rate of the auxiliary optical mode. Therefore, our proposal provides an effective method to manipulate and enhance the one-way Gaussian steering between the two modes.

In this short review article, we aim to provide physicists not working within the quantum computing community a hopefully easy-to-read introduction to the state of the art in the field, with minimal mathematics involved. In particular, we focus on what is termed the Noisy Intermediate Scale Quantum era of quantum computing. We describe how this is increasingly seen to be a distinct phase in the development of quantum computers, heralding an era where we have quantum computers that are capable of doing certain quantum computations in a limited fashion, and subject to certain constraints and noise. We further discuss the prominent algorithms that are believed to hold the most potential for this era, and also describe the competing physical platforms on which to build a quantum computer that have seen the most success so far. We then talk about the applications that are most feasible in the near-term, and finish off with a short discussion on the state of the field. We hope that as non-experts read this article, it will give context to the recent developments in quantum computers that have garnered much popular press, and help the community understand how to place such developments in the timeline of quantum computing.

We review a recent progress of a superconductivity and a charge Kondo effect mediated by valence skippers which are elements skipping the valence state. To understand the valence skipping phenomenon, we introduce a negative-U effect phenomenologically, and we show an origin of the negative-U effect, a superconductivity and charge Kondo effect based on the negative-U effect. We also show a new mechanism in which the valence skipping phenomenon and charge Kondo effect are understood unifiedly by the pair hopping interaction. As an experimental progress, we review a charge Kondo effect and a superconductivity discovered in Tl-doped PbTe. Especially, we focus on a drastic increase of the inverse of the relaxation time (1/T₁) observed around the Kondo temperature by the nuclear magnetic resonance experiment, and we suggest a possible theoretical scenario on the basis of the effective model with the pair hopping interaction. Finally, we discuss the related materials, and describe the perspective of valence skipping phenomenon.