There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

Quantum networks provide opportunities and challenges across a range of intellectual and technical frontiers, including quantum computation, communication and metrology. The realization of quantum networks composed of many nodes and channels requires new scientific capabilities for generating and characterizing quantum coherence and entanglement. Fundamental to this endeavour are quantum interconnects, which convert quantum states from one physical system to those of another in a reversible manner. Such quantum connectivity in networks can be achieved by the optical interactions of single photons and atoms, allowing the distribution of entanglement across the network and the teleportation of quantum states between nodes.

The quantum internet

We review the field of cavity optomechanics, which explores the interaction between electromagnetic radiation and nano- or micromechanical motion This review covers the basics of optical cavities and mechanical resonators, their mutual optomechanical interaction mediated by the radiation pressure force, the large variety of experimental systems which exhibit this interaction, optical measurements of mechanical motion, dynamical backaction amplification and cooling, nonlinear dynamics, multimode optomechanics, and proposals for future cavity quantum optomechanics experiments In addition, we describe the perspectives for fundamental quantum physics and for possible applications of optomechanical devices

Cavity Optomechanics

Bose-Einstein condensation (BEC) has been observed in a dilute gas of sodium atoms. A Bose-Einstein condensate consists of a macroscopic population of the ground state of the system, and is a coherent state of matter. In an ideal gas, this phase transition is purely quantum-statistical. The study of BEC in weakly interacting systems which can be controlled and observed with precision holds the promise of revealing new macroscopic quantum phenomena that can be understood from first principles.

Bose-Einstein condensation in a gas of sodium atoms

We report the Bose-Einstein condensation (BEC) of the most magnetic element, dysprosium. The Dy BEC is the first for an open f-shell lanthanide (rare-earth) element and is produced via forced evaporation in a crossed optical dipole trap loaded by an unusual, blue-detuned and spin-polarized narrowline magneto-optical trap. Nearly pure condensates of 1.5 × 10(4) (164)Dy atoms form below T = 30 nK. We observe that stable BEC formation depends on the relative angle of a small polarizing magnetic field to the axis of the oblate trap, a property of trapped condensates only expected in the strongly dipolar regime. This regime was heretofore only attainable in Cr BECs via a Feshbach resonance accessed at a high-magnetic field.

Strongly dipolar Bose-Einstein condensate of dysprosium.

We report the first quantum degenerate dipolar Fermi gas, the realization of which opens a new frontier for exploring strongly correlated physics and, in particular, quantum liquid crystalline phases. A quantum degenerate Fermi gas of the most magnetic atom $^{161}\mathrm{Dy}$ is produced by laser cooling to $10\text{ }\text{ }\ensuremath{\mu}\mathrm{K}$ before sympathetically cooling with ultracold, bosonic $^{162}\mathrm{Dy}$. The temperature of the spin-polarized $^{161}\mathrm{Dy}$ is a factor $T/{T}_{F}=0.2$ below the Fermi temperature ${T}_{F}=300\text{ }\text{ }\mathrm{nK}$. The cotrapped $^{162}\mathrm{Dy}$ concomitantly cools to approximately ${T}_{c}$ for Bose-Einstein condensation, thus realizing a novel, nearly quantum degenerate dipolar Bose-Fermi gas mixture. Additionally, we achieve the forced evaporative cooling of spin-polarized $^{161}\mathrm{Dy}$ without $^{162}\mathrm{Dy}$ to $T/{T}_{F}=0.7$. That such a low temperature ratio is achieved may be a first signature of universal dipolar scattering.

https://physics.aps.org/featured-article-pdf/10.1103/PhysRevLett.108.215301

Quantum degenerate dipolar Fermi gas.

After the first paper regarding the Best Worst Method (BWM) was published in Omega in 2015 (J. Rezaei, Best-worst multi-criteria decision-making method, Omega 53 (2015) 49–57), it has attracted many scholars’ attention due to the efficiency of this method in reducing the times of pairwise comparisons and the good performance in maintaining consistency between judgments. Lots of researches related to this method have been published over the past several years. This paper concentrates on the state-of-the-art survey of the BWM based on the in-depth analysis over the publications concerning this method published from 2015 to 26th, January 2019. This paper intends to answer five questions about the BWM: (1) How does this method perform in bibliometric analysis? (2) Why to propose this method and what is it? (3) Which integrations that the BWM were focused on and which areas did they apply to? (4) What extensions of this method were investigated? (5) What are the challenges and future research directions regarding this method? In view of the fact that the research on this method is still in infancy, this paper has guiding significance for the later research related to the BWM. From the theoretical point of view, the reasonable value of consistency ratio, the inconsistency improving methods, the uncertain extensions of the BWM and the techniques for solving multi-optimality model in the BWM are good research issues that need to be further investigated in the future. From the perspective of application, the software packages for this method, the various integrations of this method, the wider application areas, and the international cooperation on this method are good topics to consider.

The state-of-the-art survey on integrations and applications of the best worst method in decision making: Why, what, what for and what's next?

We propose that condensed-matter phenomena involving the spontaneous emergence and dynamics of crystal lattices can be realized using Bose–Einstein condensates coupled to multimode optical cavities. It is known that, in the case of a transversely pumped single-mode cavity, the atoms crystallize at either the even or the odd antinodes of the cavity mode at sufficient pump laser intensity, thus spontaneously breaking a discrete translational symmetry. Here we demonstrate that, in multimode cavities, crystallization involves the spontaneous breaking of a continuous translational symmetry, through a variant of Brazovskii’s transition, thus paving the way for realizations of compliant lattices and associated phenomena, such as dislocations, frustration, glassiness and even supersolidity, in ultracold atomic settings, where quantum effects have a dominant role. We apply a functional-integral formalism to explore the role of fluctuations in this correlated many-body system, to calculate their effect on the threshold for ordering, and to determine their imprint on the correlations of the light emitted from the cavity. Optical lattices, generated by interfering laser beams, provide a platform for observing condensed-matter phenomena in ultracold-atom systems. By extending the lattice idea to a multimode cavity, it should be possible to observe even more complex effects, such as frustration, crystallization, glass phases and supersolidity.

Emergent crystallinity and frustration with Bose–Einstein condensates in multimode cavities

Ultracold dysprosium gases, with a magnetic moment 10 times that of alkali atoms and equal only to terbium as the most magnetic atom, are expected to exhibit a multitude of fascinating collisional dynamics and quantum dipolar phases, including quantum liquid crystal physics. We report the first laser cooling and trapping of half a billion Dy atoms using a repumper-free magneto-optical trap (MOT) and continuously loaded magnetic confinement, and we characterize the trap recycling dynamics for bosonic and fermionic isotopes. The first inelastic collision measurements in the few partial wave, 100 microK-1 mK, regime are made in a system possessing a submerged open electronic f shell. In addition, we observe unusual stripes of intra-MOT <10 microK sub-Doppler cooled atoms.

/pdf/trapping-ultracold-dysprosium-a-highly-magnetic-gas-for-2jjmsu0c4z.pdf

Benjamin Lev

Papers

Strongly dipolar Bose-Einstein condensate of dysprosium.

Quantum degenerate dipolar Fermi gas.

The state-of-the-art survey on integrations and applications of the best worst method in decision making: Why, what, what for and what's next?

Emergent crystallinity and frustration with Bose–Einstein condensates in multimode cavities

Trapping ultracold dysprosium: a highly magnetic gas for dipolar physics.