The Miscible-Immiscible Quantum Phase Transition in Coupled Two-Component Bose-Einstein Condensates in 1D Optical Lattices

Using numerical techniques, we study the miscible-immiscible quantum phase transition in a linearly coupled binary Bose-Hubbard model Hamiltonian that can describe low-energy properties of a two-component Bose-Einstein condensate in optical lattices. With the quantum many-body ground state obtained from density matrix renormalization group algorithm, we calculate the characteristic physical quantities of the phase transition controlled by the linear coupling between two components. Furthermore we calculate the Binder cumulant to determine the critical point and draw the phase diagram. The strong-coupling expansion shows that in the Mott insulator regime the model Hamiltonian can be mapped to a spin 1/2 XXZ model with a transverse magnetic field.Comment: 10 pages, 10 figures, submitted to Phys. Rev.

Phase separation and pattern formation in a binary Bose-Einstein condensate

The miscibility-immiscibility phase transition in binary Bose-Einstein condensates (BECs) can be controlled by a coupling between the two components. Here we propose a new scheme that uses coupling-induced pattern formation to test the Kibble-Zurek mechanism (KZM) of topological-defect formation in a quantum phase transition. For a binary BEC in a ring trap we find that the number of domains forming the pattern scales as a function of the coupling quench rate with an exponent as predicted by the KZM. For a binary BEC in an elongated harmonic trap we find a different scaling law due to the transition being spatially inhomogeneous. We perform a “quantum simulation” of the harmonically trapped system in a ring trap to verify the scaling exponent

Quantum enhanced measurement of rotations with a spin-1 Bose-Einstein condensate in a ring trap

We present a model of a spin-squeezed rotation sensor utilizing the Sagnac effect in a spin-1 Bose-Einstein condensate in a ring trap. The two input states for the interferometer are seeded using Raman pulses with Laguerre-Gauss beams and are amplified by the bosonic enhancement of spin-exchange collisions, resulting in spin-squeezing and potential quantum enhancement of the interferometry. The ring geometry has an advantage over separated beam path atomic rotation sensors due to the uniform condensate density. We model the interferometer both analytically and numerically for realistic experimental parameters and find that significant quantum enhancement is possible, but this enhancement is partially degraded when working in a regime with strong atomic interactions

Causality and defect formation in the dynamics of an engineered quantum phase transition in a coupled binary Bose-Einstein condensate

Continuous phase transitions occur in a wide range of physical systems, and provide a context for the study of non-equilibrium dynamics and the formation of topological defects. The Kibble-Zurek (KZ) mechanism predicts the scaling of the resulting density of defects as a function of the quench rate through a critical point, and this can provide an estimate of the critical exponents of a phase transition. In this work we extend our previous study of the miscible-immiscible phase transition of a binary Bose-Einstein condensate (BEC) composed of two hyperfine states in which the spin dynamics are confined to one dimension [J. Sabbatini et al., Phys. Rev. Lett. 107, 230402 (2011)]. The transition is engineered by controlling a Hamiltonian quench of the coupling amplitude of the two hyperfine states, and results in the formation of a random pattern of spatial domains. Using the numerical truncated Wigner phase space method, we show that in a ring BEC the number of domains formed in the phase transitions scales as predicted by the KZ theory. We also consider the same experiment performed with a harmonically trapped BEC, and investigate how the density inhomogeneity modifies the dynamics of the phase transition and the KZ scaling law for the number of domains. We then make use of the symmetry between inhomogeneous phase transitions in anisotropic systems, and an inhomogeneous quench in a homogeneous system, to engineer coupling quenches that allow us to quantify several aspects of inhomogeneous phase transitions. In particular, we quantify the effect of causality in the propagation of the phase transition front on the resulting formation of domain walls, and find indications that the density of defects is determined during the impulse to adiabatic transition after the crossing of the critical point.Comment: 23 pages, 10 figures. Minor corrections, typos, additional referenc

Inter-rater agreement of CDC criteria and ASEPSIS score in assessing surgical site infections after cesarean section: a prospective observational study

ObjectiveTo assess and compare the inter-rater agreement of the CDC criteria and the ASEPSIS score in identifying surgical site infections after cesarean section.MethodsProspective observational study including 110 patients subjected to a cesarean section at our institution. Surgical wounds were managed according to standard care and were photographed on the third, seventh, and thirtieth postoperative day or during any evaluation in case of complications. Three expert surgeons reviewed the prospectively gathered data and photographs and classified each wound using CDC criteria and the ASEPSIS score. The inter-rater agreements of CDC criteria and ASEPSIS score were determined with Krippendorff's Alpha with linear weights and compared with a confidence interval approach.ResultsThe weighted α coefficient for CDC criteria was 0.587 (95%CI, 0.411–0.763, p < 0.001, “moderate” agreement according to Altman's interpretation of weighted agreement coefficient), while the weighted α coefficient for the ASEPSIS score was 0.856 (95%CI, 0.733–0.980, p < 0.001, “very good” agreement).ConclusionASEPSIS score presents a “very good” inter-rater agreement for surgical site infections identification after cesarean, resulting in a more objective method than CDC criteria (“moderate” inter-rater agreement). ASEPSIS score could represent an objective tool for managing and monitoring surgical site infections after cesarean section, also by photographic evaluation

Diel behavior from temporally scheduled hauling of the red shrimps Aristeus antennatus and Aristaeomorpha foliacea in the Spartivento Canyon (Southern Sardinia, Italy)

The Crustacean Society Summer Meeting (TCSSM) - 10th Colloquium Crustacea Decapoda Mediterranea (CCDM), 3-7 June 2012, Athens, GreeceThe red shrimp Aristeus antennatus (Risso 1816) and the giant red shrimp Aristaeomorpha foliacea (Risso 1827) are one of the most important and exploited demersal (400-800 m) resources in the Western Mediterranean Sea1. Although their bathymetric distribution has been investigated, information on its variation over the 24-h scale as result of rhythmic nektobenthic displacements on population is scarce2. In this context, we carried out a temporally scheduled hauling within different depths strata in order to characterize the displacement rhythms of both species, in relation to the local topographic and oceanographic conditionsPeer Reviewe