Predominant Magnetic States in Hubbard Model on Anisotropic Triangular Lattices

Using an optimization variational Monte Carlo method, we study the half-filled-band Hubbard model on anisotropic triangular lattices, as a continuation of the preceding study [J. Phys. Soc. Jpn 75, 074707 (2006)]. We introduce two new trial states: (i) A coexisting state of (\pi,\pi)-antiferromagnetic (AF) and a d-wave singlet gaps, in which we allow for a band renormalization effect, and (ii) a state with an AF order of 120^\circ spin structure. In both states, a first-order metal-to-insulator transition occurs at smaller U/t than that of the pure d-wave state. In insulating regimes, magnetic orders always exist; an ordinary (\pi,\pi)-AF order survives up to t'/t\sim 0.9 (U/t=12), and a 120^\circ-AF order becomes dominant for t'/t \gsim 0.9. The regimes of the robust superconductor and of the nonmagnetic insulator the preceding study proposed give way to these magnetic domains.Comment: 11 pages, 14 figure

Nonlocal quantum gate on quantum continuous variables with minimum resources

We experimentally demonstrate, with an all-optical setup, a nonlocal deterministic quantum non-demolition interaction gate applicable to quantum states at nodes separated by a physical distance and connected by classical communication channels. The gate implementation, based on entangled states shared in advance, local operations, and classical communication, runs completely in parallel fashion at both the local nodes, requiring minimum resource. The nondemolition character of the gate up to the local unitary squeezing is verified by the analysis using several coherent states. A genuine quantum nature of the gate is confirmed by the capability of deterministically producing an entangled state at the output from two separable input states. The all-optical nonlocal gate operation can be potentially incorporated into distributed quantum computing with atomic or solid state systems as a cross-processor unitary operation.Comment: 7 pages, 4 figure

On the Terrestrial Earthworm Fauna of Yamagata Prefecture, northeastern Japan

We conducted to collect earthworms in order to clarify the earthworm fauna of Yamagata Prefecture. We could collect 16 species belonging to two families including two undescribed species from six localities. To our knowledge, it is first time to record Pheretima aokii, P. megascolidioides, P. micronaria and Aporrectodea caliginosa from Yamagata Prefecture. Therefore, except for two species which could not identified as known species, 18 valid species of earthworms exist in Yamagata Prefecture including our result. Keywords : earthworm fauna, Megascolecidae, Lumbricidae, Oligochaeta, Yamagata Prefectur

Demonstration of a Controlled-Phase Gate for Continuous-Variable One-Way Quantum Computation

We experimentally demonstrate a controlled-phase gate for continuous variables in a fully measurement-based fashion. In our scheme, the two independent input states of the gate, encoded in two optical modes, are teleported into a four-mode Gaussian cluster state. As a result, one of the entanglement links present in the initial cluster state appears in the two unmeasured output modes as the corresponding entangling gate acting on the input states. The genuine quantum character of this gate becomes manifest and is verified through the presence of entanglement at the output for a product two-mode coherent input state. By combining our controlled-phase gate with the recently reported module for universal single-mode Gaussian operations [R. Ukai et al., Phys. Rev. Lett. 106, 240504 (2011)], it is possible to implement universal Gaussian operations on arbitrary multi-mode quantum optical states in form of a fully measurement-based one-way quantum computation.Comment: 4 pages, 3 figure

Variational Monte Carlo studies of a t-J model on an anisotropic triangular lattice

With the insulating phase of \kappa-(BEDT-TTF)_2X in mind, we study a t-J model on an anisotropic triangular lattice, where the hopping integral is t' in one of the three directions, using a variational Monte Carlo method. By changing the value of t'/t, we study the stability of superconducting (SC) states with d- and d+id-wave symmetries and of an antiferromagnetic (AF) state. As t'/t decreases from 1, the stable state immediately switches from the d+id wave to the d wave. The AF state is stabilized from the normal spin liquid state for t'/t\lsim 0.7 at half filling. We also take account of Nagaoka ferromagnetism and a phase separation.Comment: 4 pages, 3 figure