Phase diagram of the hardcore Bose-Hubbard model on a checkerboard superlattice

We obtain the complete phase diagram of the hardcore Bose-Hubbard model in the presence of a period-two superlattice in two and three dimensions. First we acquire the phase boundaries between the superfluid phase and the `trivial' insulating phases of the model (the completely-empty and completely-filled lattices) analytically. Next, the boundary between the superfluid phase and the half-filled Mott-insulating phase is obtained numerically, using the stochastic series expansion (SSE) algorithm followed by finite-size scaling. We also compare our numerical results against the predictions of several approximation schemes, including two mean-field approaches and a fourth-order strong-coupling expansion (SCE), where we show that the latter method in particular is successful in producing an accurate picture of the phase diagram. Finally, we examine the extent to which several approximation schemes, such as the random phase approximation and the strong-coupling expansion, give an accurate description of the momentum distribution of the bosons inside the insulating phases.Comment: 11 pages, 7 figure

Reexamination of the evidence for entanglement in the D-Wave processor

A recent experiment [Lanting et al., PRX, (2014)] claimed to provide evidence of up to $8$-qubit entanglement in a D-Wave quantum annealing device. However, entanglement was measured using qubit tunneling spectroscopy, a technique that provides indirect access to the state of the system at intermediate times during the anneal by performing measurements at the end of the anneal with a probe qubit. In addition, an underlying assumption was that the quantum transverse-field Ising Hamiltonian, whose ground states are already highly entangled, is an appropriate model of the device, and not some other (possibly classical) model. This begs the question of whether alternative, classical or semiclassical models would be equally effective at predicting the observed spectrum and thermal state populations. To check this, we consider a recently proposed classical rotor model with classical Monte Carlo updates, which has been successfully employed in describing features of earlier experiments involving the device. We also consider simulated quantum annealing with quantum Monte Carlo updates, an algorithm that samples from the instantaneous Gibbs state of the device Hamiltonian. Finally, we use the quantum adiabatic master equation, which cannot be efficiently simulated classically, and which has previously been used to successfully capture the open system quantum dynamics of the device. We find that only the master equation is able to reproduce the features of the tunneling spectroscopy experiment, while both the classical rotor model and simulated quantum annealing fail to reproduce the experimental results. We argue that this bolsters the evidence for the reported entanglement.Comment: 12 pages, 15 figures. v2: Updated to published versio

Excitation Gap from Optimized Correlation Functions in Quantum Monte Carlo Simulations

We give a prescription for finding optimized correlation functions for the extraction of the gap to the first excited state within quantum Monte Carlo simulations. We demonstrate that optimized correlation functions provide a more accurate reading of the gap when compared to other `non-optimized' correlation functions and are generally characterized by considerably larger signal-to-noise ratios. We also analyze the cost of the procedure and show that it is not computationally demanding. We illustrate the effectiveness of the proposed procedure by analyzing several exemplary many-body systems of interacting spin-1/2 particles.Comment: 11 pages, 5 figure

Perancangan Panduan Meditasi Singkat Untuk Umat Buddha Theravada

Perancangan ini merupakan sebuah panduan yang dibuat karena melihat permasalahan kurangnya minat umat Buddha Theravada sekarang terhadap meditasi.Meditasi adalah salah satu cara beribadah dalam agama Buddha yang juga memiliki banyak manfaat bagi kehidupan.Umat Buddha sekarang seringkali mengabaikan meditasi dengan banyak alasan, apalagi dengan mobilitas masyarakatnya yang tinggi sekarang ini.Untuk mengatasi hal tersebut, dibuatlah perancangan ini. Perancangan ini berupa digital card yang dibagikan secara periodik lewat media sosial online, yaitu Facebook dan Twitter dengan melihat banyaknya masyarakat sekarang termasuk umat Buddha yang sangat dekat dengan internet dan sosial media online. Desain dibuat dengan warna, huruf dan layout yang lembut untuk menunjang suasana meditasi.Rangkaian digital card ini berjudul Soulution (Solusi untuk mencapai batin yang sehat)

Hexagonal Structure of Baby Skyrmion Lattices

We study the zero-temperature crystalline structure of baby Skyrmions by applying a full-field numerical minimization algorithm to baby Skyrmions placed inside different parallelogramic unit-cells and imposing periodic boundary conditions. We find that within this setup, the minimal energy is obtained for the hexagonal lattice, and that in the resulting configuration the Skyrmion splits into quarter-Skyrmions. In particular, we find that the energy in the hexagonal case is lower than the one obtained on the well-studied rectangular lattice, in which splitting into half-Skyrmions is observed.Comment: RevTeX, 7 pages, 6 figure

Perancangan Audio Visual Seni Bantengan Di Kota Batu

Seni Bantengan adalah seni tradisional Jawa Timur yang banyak ditemukan di Kota Batu, Malang. Masih banyak masyarakat di dalam maupun di luar Malang Raya yang belum mengenal seni ini. Padahal jika dikenalkan dan dipromosikan dengan baik, seni Bantengan bisa berpotensi menjadi wisata budaya Kota Batu. Tujuan dari perancangan ini adalah untuk memperkenalkan dan memberikan informasi kepada masyarakat Indonesia akan seni Bantengan melalui video ilustrasi 2D. Dengan menggunakan teknik ilustrasi, efek paralaks, dan efek gerak grafis, serta penyebaran yang dilakukan melalui media sosial dan website, maka informasi mengenai seni ini bisa disampaikan dan dikenalkan dengan lebih menarik dan efektif