146 research outputs found
Quantum information approach to the quantum phase transition in the Kitaev honeycomb model
Kitaev honeycomb model with topological phase transition at zero temperature
is studied using quantum information method. Based on the exact solution of the
ground state, the mutual information between two nearest sites and between two
bonds with longest distance are obtained. It is found that the mutual
information show some singularities at the critical point where the ground
state of the system transits from gapless phase to gapped phase. The
finite-size effects and scalar behavior are also studied. The mutual
information can serve as good indicators of the topological phase transition,
since the mutual information catches some global correlation properties of the
system. Meanwhile, this method has other advantages such that the phase
transition can be determined easily and the order parameters are not required
previously, for the order parameters of some topological phase transitions are
hard to know.Comment: 8 pages, 7 figures, published versio
Entanglement-assisted local operations and classical communications conversion in the quantum critical systems
Conversions between the ground states in quantum critical systems via
entanglement-assisted local operations and classical communications (eLOCC) are
studied. We propose a new method to reveal the different convertibility by
local operations when a quantum phase transition occurs. We have studied the
ground state local convertibility in the one dimensional transverse field Ising
model, XY model and XXZ model. It is found that the eLOCC convertibility sudden
changes at the phase transition points. In transverse field Ising model the
eLOCC convertibility between the first excited state and the ground state are
also distinct for different phases. The relation between the order of quantum
phase transitions and the local convertibility is discussed.Comment: 7 pages, 5 figures, 5 table
Colorectal cancer screening with fecal occult blood test: A 22-year cohort study.
The aim of the present study was to investigate the efficacy of colorectal cancer (CRC) screening with a three-tier fecal occult blood test (FOBT) in the Chinese population. The study was performed between 1987 and 2008 at the Beijing Military General Hospital, in a cohort of army service males and females aged >50 years. Between 1987 and 2005, a three-tier screening program, comprising guaiac-based FOBTs (gFOBTs), followed by immunochemical FOBTs for positive guaiac test samples and then colonoscopy for positive immunochemical test subjects, was performed annually. The cohort was followed up until 2008. The cohort included 5,104 subjects, of which, 3,863 subjects participated in screening (screening group) and 1,241 did not (non-screening group). The two groups did not differ in age, gender or other major risk factors for colon cancer. Overall, 36 CRCs occurred in the screening group and 21 in the non-screening group. Compared with the non-screening group, the relative risk for the incidence and mortality of CRC was 0.51 [95% confidence interval (CI), 0.30-0.87] and 0.36 (95% CI, 0.18-0.71), respectively, in the screening group. The general sensitivity of this three-tier FOBT was 80.6% (95% CI, 65.3-91.1). Thus, annual screening using the three-tier FOBT program may reduce the CRC incidence and mortality rate
- …