通过量子隐形传态探测有限温度下的量子临界点

探测量子临界点处的涌现连续对称性

Detecting emergent continuous symmetries at quantum criticality

提出一种基于张量网络的算法，无需低能有效场论先验知识即可从任意量子自旋链基态数值提取涌现守恒流的格点算符近似，成功获取格点 Kac-Moody 生成元，并可寻找可积模型的局部运动积分与局部母哈密顿量。

Detecting Quantum Critical Points using Bipartite Fluctuations

We show that the concept of bipartite fluctuations F provides a very efficient tool to detect quantum phase transitions in strongly correlated systems. Using state of the art numerical techniques complemented with analytical arguments, we investigate paradigmatic examples for both quantum spins and bosons. As compared to the von Neumann entanglement entropy, we observe that F allows to find quantum critical points with a much better accuracy in one dimension. We further demonstrate that F can be successfully applied to the detection of quantum criticality in higher dimensions with no prior kno…

Detecting topological orders through continuous quantum phase transition

We study a continuous quantum phase transition that breaks a $Z_2$ symmetry. We show that the transition is described by a new critical point which does not belong to the Ising universality class, despite the presence of well defined symmetry breaking order parameter. The new critical point arises since the transition not only break the $Z_2$ symmetry, it also changes the topological/quantum order in the two phases across the transition. We show that the new critical point can be identified in experiments by measuring critical exponents. So measuring critical exponents and identifying new crit…

Detecting a quantum critical point in topological SN junctions

A spin-orbit coupled quantum wire, with one end proximate to an s-wave superconductor, can become a topological superconductor, with a Majorana mode localized at each end of the superconducting region. It was recently shown that coupling one end of such a topological superconductor to $two$ normal channels of interacting electrons leads to a novel type of frustration and a quantum critical point when both channels couple with equal strength. We propose an experimental method to access this critical point in a $single$ quantum wire and show its resilience to disorder.

通过Schwinger模型中的纠缠探测临界点

Detecting the critical point through entanglement in Schwinger model

本文通过经典硬件上的量子模拟研究带θ项的大质量Schwinger模型相图，发现量子临界点可由纠缠熵的尖锐极大值和纠缠谱的能隙闭合点探测，并揭示临界点位置随化学势变化。

Detecting quantum critical points in the $t-t'$ Fermi-Hubbard model via complex network theory

A considerable success in phenomenological description of high-T$_{\rm c}$ superconductors has been achieved within the paradigm of Quantum Critical Point (QCP) - a parental state of a variety of exotic phases that is characterized by dense entanglement and absence of well-defined quasiparticles. However, the microscopic origin of the critical regime in real materials remains an open question. On the other hand, there is a popular view that a single-band $t-t'$ Hubbard model is the minimal model to catch the main relevant physics of superconducting compounds. Here, we suggest that emergence of…

Detecting Topological Quantum Phase Transitions via the c-Function

We propose the c-function as a new and accurate probe to detect the location of topological quantum critical points. As a direct application, we consider a holographic model which exhibits a topological quantum phase transition between a topologically trivial insulating phase and a gapless Weyl semimetal. The quantum critical point displays a strong Lifshitz-like anisotropy in the spatial directions and the quantum phase transition does not follow the standard Landau paradigm. The c-function robustly shows a global feature at the quantum criticality and distinguishes with great accuracy the tw…

通过子系统的纠缠谱检测临界点的（涌现）连续对称性

Detecting (emergent) continuous symmetry of criticality via subsystem's entanglement spectrum

本文提出一种无偏方法，通过计算子系统的约化密度矩阵，利用纠缠谱中的安德森塔状态来识别量子多体系统中临界点的底层（涌现）对称性。

Detecting Many-Body-Localization Length with Cold Atoms

Considering ultracold atoms in optical lattices, we propose experimental protocols to study many-body localization (MBL) length and criticality in quench dynamics. Through numerical simulations with exact diagonalization, we show that in the MBL phase the perturbed density profile following a local quench remains exponentially localized in post-quench dynamics. The size of this density profile after long-time-dynamics defines a localization length, which tends to diverge at the MBL-to-ergodic transition as we increase the system size. The determined localization transition point agrees with pr…

Detecting Topological Order at Finite Temperature Using Entanglement Negativity

We propose a diagnostic for finite temperature topological order using `topological entanglement negativity', the long-range component of a mixed-state entanglement measure. As a demonstration, we study the toric code model in $d$ spatial dimension for $d$=2,3,4, and find that when topological order survives thermal fluctuations, it possesses a non-zero topological entanglement negativity, whose value is equal to the topological entanglement entropy at zero temperature. Furthermore, we show that the Gibbs state of 2D and 3D toric code at any non-zero temperature, and that of 4D toric code abov…

利用色心探测临界自旋液体中的分数化

Detecting Fractionalization in Critical Spin Liquids using Color Centers

本文理论研究利用金刚石NV色心弛豫测量探测两类典型量子自旋液体，通过自旋谱函数中的Stoner连续谱、集体模式及幂律展宽识别自旋子分数化信号。