We propose a series of simple 2d lattice interacting fermion models that we demonstrate at low energy describe bosonic symmetry protected topological (SPT) states and quantum phase transitions between them. This is because due to interaction the fermions are gapped both at the boundary of the SPT states and at the bulk quantum phase transition, thus these models at low energy can be described completely by bosonic degrees of freedom. We show that the bulk of these models is described by a Sp(N ) principal chiral model with a topological Θ-term, whose boundary is described by a Sp(N ) principal chiral model with a Wess-Zumino-Witten term at level-1. The quantum phase transition between SPT states in the bulk is tuned by a particular interaction term, which corresponds to tuning Θ in the field theory and the phase transition occurs at Θ = π. The simplest version of these models with N = 1 is equivalent to the familiar O(4) nonlinear sigma model (NLSM) with a topological term, whose boundary is a (1 + 1)d conformal field theory with central charge c = 1. After breaking the O(4) symmetry to its subgroups, this model can be viewed as bosonic SPT states with U(1), or Z2 symmetries, etc. All these fermion models including the bulk quantum phase transitions can be simulated with determinant Quantum Monte Carlo method without the sign problem. Recent numerical results strongly suggest that the quantum disordered phase of the O(4) NLSM with precisely Θ = π is a stable (2 + 1)d conformal field theory (CFT) with gapless bosonic modes.

The theory of phase control of coherence, entanglement and quantum steering is developed for an optomechanical system composed of a single mode cavity containing a partially transmitting dielectric membrane and driven by short laser pulses. The membrane divides the cavity into two mutually coupled optomechanical cavities resulting in an effective three-mode closed loop system, two field modes of the two cavities and a mechanical mode representing the oscillating membrane. The closed loop in the coupling creates interfering channels which depend on the relative phase of the coupling strengths of the field modes to the mechanical mode. Populations and correlations of the output modes are calculated analytically and show several interesting phase dependent effects such as reversible population transfer from one field mode to the other, creation of collective modes, and induced coherence without induced emission. We find that these effects result from perfect mutual coherence between the field modes which is preserved even if one of the modes is not populated. The inseparability criterion for the output modes is also investigated and we find that entanglement may occur only between the field modes and the mechanical mode. We show that depending on the phase, the field modes can act on the mechanical mode collectively or individually resulting, respectively, in tripartite or bipartite entanglement. In addition, we examine the phase sensitivity of quantum steering of the mechanical mode by the field modes. Deterministic phase transfer of the steering from bipartite to collective is predicted and optimum steering corresponding to perfect EPR state can be achieved. These different types of quantum steering can be distinguished experimentally by measuring the coincidence rate between two detectors adjusted to collect photons of the output cavity modes. In particular, we find that the minima of the interference pattern of the coincidence rate signal the bipartite steering, while the maxima signal the collective steering. distant system, as considered in the original Einstein-Podolsky-Rosen (EPR) paradox [10]. The EPR steering allows two parties to verify the shared entanglement even if one measurement device is untrusted, which makes it an essential resource for one-sided device independent quantum cryptography [11][12][13][14][15][16], one-way quantum computing [17,18], secure quantum teleportation [19,20], and subchannel discrimination [21].Recent studies have revealed that coherence is closely related to entanglement and quantum steering. It was pointed out by Suzuki et al [22] that entanglement can be detected from interference fringes in atom-photon systems. It has also been shown that the coherence in a system and entanglement between that system and another initially incoherent one are quantitatively, or operationally, equivalent [23]. The power of quantum steering for the generation of coherence has also been demonstrated [24,25]. It has been shown that the presence of mutual coherence among two systems may have a ...

This article addresses the impact of social capital on college graduate employment. After reviewing the literature, the authors analyze data collected by Peking University from 34 universities in 2005 and use statistical analysis to clarify the impact of social capital on students' choice of employment or further study, job placement rate, starting salary and job satisfaction. The study concludes that social capital differs for students from different social backgrounds; personal social capital affects students' choice to seek employment, but family social capital impacts their choice of further study; both family and personal social capital have a significant positive impact on graduates' placement rate, starting salary, and job satisfaction; and social capital has a more significant and positive impact on job placement rates for graduates at the associate's and undergraduate degree levels than for those at the master's level and above.

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