We define a multiparty entanglement measure, called generalized geometric measure, that can detect and quantify genuine multiparty entanglement for any number of parties. The quantum phase transitions in exactly solvable models like the anisotropic XY model can be detected by this measure. We find that the multisite measure can be a useful tool to detect quantum phenomena in more complex systems like quasi 2D and 2D frustrated Heisenberg antiferromagnets. We propose an order parameter, called bound generalized geometric measure, in the spirit of bound quantum states, that can recognize the gapless and gapped phases of the frustrated models by its sign. The vanishing of the order parameter therefore signals the transition between such phases.
Topology in quantum matter is typically associated with gapped phases. For example, in symmetry protected topological (SPT) phases, the bulk energy gap localizes edge modes near the boundary. In this work we identify a new mechanism that leads to topological phases which are not only gapless but where the absence of a gap is essential. These `intrinsically gapless SPT phases' have no gapped counterpart and are hence also distinct from recently discovered examples of gapless SPT phases. The essential ingredient of these phases is that on-site symmetries act in an anomalous fashion at low energi…
We study the dynamics of discrete-time quantum walk using quantum coin operations, $\hat{C}(θ_1)$ and $\hat{C}(θ_2)$ in time-dependent periodic sequence. For the two-period quantum walk with the parameters $θ_1$ and $θ_2$ in the coin operations we show that the standard deviation [$σ_{θ_1, θ_2} (t)$] is the same as the minimum of standard deviation obtained from one of the one-period quantum walks with coin operations $θ_1$ or $θ_2$, $σ_{θ_1, θ_2}(t) = \min \{σ_{θ_1}(t), σ_{θ_2}(t) \}$. Our numerical result is analytically corroborated using the dispersion relation obtained from the continuum …
We introduce topological invariants for gapless systems and study the associated boundary phenomena. More generally, the symmetry properties of the low-energy conformal field theory (CFT) provide discrete invariants, establishing the notion of symmetry-enriched quantum criticality. The charges of nonlocal scaling operators, or more generally of symmetry defects, are topological and imply the presence of localized edge modes. We primarily focus on the $1+1d$ case where the edge has a topological degeneracy, whose finite-size splitting can be exponential or algebraic in system size depending on …
In three dimensions, gapped phases can support "fractonic" quasiparticle excitations, which are either completely immobile or can only move within a low-dimensional submanifold, a peculiar topological phenomenon going beyond the conventional framework of topological quantum field theory. In this work we explore fractonic topological phases using three-dimensional coupled wire constructions, which have proven to be a successful tool to realize and characterize topological phases in two dimensions. We find that both gapped and gapless phases with fractonic excitations can emerge from the models.…
Thermal robustness of sensing quantum phases of matter via qubit probes
FZU - Institute of Physics of the Czech Academy of Sciences（捷克科学院物理研究所）；Department of Physics, King’s College London（伦敦国王学院物理系）；School of Physics, Trinity College Dublin（都柏林三一学院物理学院）
Single-copy entanglement in a gapped quantum spin chain
定义了给定多体系统的单拷贝纠缠[J. J. J. Cramer，Phys. Rev. A. 72，042112（2005）]作为从该系统的单个样本的二分物确定性地可量化的最大纠缠。对于临界（无间隙）自旋链，最近的研究表明，这正好是冯诺伊曼熵的一半[R。Orus，J. I. Latorre，J. J. Cramer，Phys. Rev. A 73，060303（R）（2006）]，其本身被定义为在渐近极限中可纠缠的：即给定系统的无限数量的副本。对于带隙系统的等效行为是什么，这是一个悬而未决的问题。在本文中，我证明了对于典型的自旋-S-Affleck-Kennedy-Lieb-Tasaki链（原型带隙链），单拷贝纠缠等于冯诺伊曼熵：即所有存在的纠缠都可以从一个样本中提取出来.
Deconfined criticality as intrinsically gapless topological state in one dimension
Institute for Advanced Study in Physics and School of Physics, Zhejiang University（浙江大学物理学院和高等研究院）；Department of Physics, Nanjing University（南京大学物理系）；University of Colorado, Boulder（科罗拉多大学博尔德分校）；Harvard University（哈佛大学）；Department of Physics, University of California, San Diego（加州大学圣地亚哥分校物理系）；Fuzhou University（福州大学）；College of Physics and Information Engineering, Fuzhou University（福州大学物理与信息工程学院）
