We have developed an efficient tensor network algorithm for spin ladders, which generates ground-state wave functions for infinite-size quantum spin ladders. The algorithm is able to efficiently compute the ground-state fidelity per lattice site, a universal phase transition marker, thus offering a powerful tool to unveil quantum many-body physics underlying spin ladders. To illustrate our scheme, we consider the two-leg and three-leg Heisenberg spin ladders with staggering dimerization. The ground-state phase diagram thus yielded is reliable, compared with the previous studies based on the density matrix renormalization group. Our results indicate that the ground-state fidelity per lattice site successfully captures quantum criticalities in spin ladders. 71.10.Fd Introduction. Tensor networks (TN) provide a convenient means to represent quantum wave functions in classical simulations of quantum many-body lattice systems, such as the matrix product states (MPS) [1][2][3][4][5] in one spatial dimension and the projected entangled-pair state (PEPS) [6][7][8] in two and higher spatial dimensions. The development of various numerical algorithms in the context of the TN representations has led to significant advances in our understanding of quantum many-body lattice systems in both one and two spatial dimensions [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. Lying between quantum lattice systems in one and two spatial dimensions, spin ladders have attracted a lot of attention, due to their intriguing critical properties. Given the importance of spin ladder systems in condensed matter physics, it is somewhat surprising that no efforts have been made to develop any efficient algorithm in the context of the TN representations.This paper aims to fill in this gap. The algorithm generates efficiently ground-state wave functions for infinite-size spin ladders. In addition, it allows to efficiently compute the ground-state fidelity per lattice site, a universal phase transition marker, thus offering a powerful tool to unveil quantum many-body physics underlying spin ladders. In fact, as argued in Refs. [18][19][20][21][22][23], the ground-state fidelity per lattice site is able to capture drastic changes of the ground-state wave functions around a critical point. To illustrate our scheme, we consider the two-leg and three-leg Heisenberg spin ladders with staggering dimerization. The ground-state phase diagram thus yielded is reliable, compared with the previous studies [24,25] based on the density matrix renormalization group (DMRG) [26]. Our results indicate that the ground-state fidelity per lattice site successfully captures quantum criticalities in spin ladders.Tensor network representation for spin ladders. Let us describe the TN representation suitable to describe a groundstate wave function for an infinite-size spin ladder. Suppose the Hamiltonian is translationally invariant under shifts by either one or two lattice sites along the legs: H = i,α h i,α , with the i, α -th plaquette Hamiltonian density h i,α...

The ground-state phase diagram of the two-dimensional t − J model is investigated in the context of the tensor network algorithm in terms of the graded Projected Entangled-Pair State representation of the ground-state wave functions. There is a line of phase separation between the Heisenberg anti-ferromagnetic state without hole and a hole-rich state. For both J = 0.4t and J = 0.8t, a systematic computation is performed to identify all the competing ground states for various dopings. It is found that, besides a possible Nagaoka's ferromagnetic state, the homogeneous regime consists of four different phases: one phase with charge and spin density wave order coexisting with a p x (p y )−wave superconducting state, one phase with the symmetry mixing of d + s−wave superconductivity in the spin-singlet channel and p x (p y )−wave superconductivity in the spin-triplet channel in the presence of an anti-ferromagnetic background, one superconducting phase with extended s−wave symmetry, and one superconducting phase with p x (p y )−wave symmetry in a ferromagnetic background.

Spontaneous symmetry breaking mechanism in quantum phase transitions manifests the existence of degenerate groundstates in broken symmetry phases. To detect such degenerate groundstates, we introduce a quantum fidelity as an overlap measurement between system groundstates and an arbitrary reference state. This quantum fidelity is shown a multiple bifurcation as an indicator of quantum phase transitions, without knowing any detailed broken symmetry, between a broken symmetry phase and symmetry phases as well as between a broken symmetry phase and other broken symmetry phases, when a system parameter crosses its critical value (i.e., multiple bifurcation point). Each order parameter, characterizing a broken symmetry phase, from each of degenerate groundstates is shown similar multiple bifurcation behavior. Furthermore, to complete the description of an ordered phase, it is possible to specify how each order parameter from each of degenerate groundstates transforms under a symmetry group that is possessed by the Hamiltonian because each order parameter is invariant under only a subgroup of the symmetry group although the Hamiltonian remains invariant under the full symmetry group. Examples are given in the quantum q-state Potts models with a transverse magnetic field by employing the tensor network algorithms based on infinite-size lattices. For any q, a general relation between the local order parameters is found to clearly show the subgroup of the Z q symmetry group. In addition, we systematically discuss the criticality in the q-state Potts model.

A systematic analysis is performed for quantum phase transitions in a two-dimensional anisotropic spin 1/2 anti-ferromagnetic XYX model in an external magnetic field. With the help of an innovative tensor network algorithm, we compute the fidelity per lattice site to demonstrate that the field-induced quantum phase transition is unambiguously characterized by a pinch point on the fidelity surface, marking a continuous phase transition. We also compute an entanglement estimator, defined as a ratio between the one-tangle and the sum of squared concurrences, to identify both the factorizing field and the critical point, resulting in a quantitative agreement with quantum Monte Carlo simulation. In addition, the local order parameter is "derived" from the tensor network representation of the system's ground state wave functions. Quantum critical phenomena are crucial in our understanding of the underlying physics in quantum manybody systems, especially in condensed matter systems, due to their relevance to high-T c superconductors, fractional quantum Hall liquids, and quantum magnets [1,2]. The latest advances in this area arise from quantum information science. Indeed, various entanglement measures have been widely applied to study condensed matter systems. Remarkably, for one-dimensional (1D) quantum systems, von-Neumann entropy, as a bipartite entanglement measure, turns out to be a good criterion to judge whether or not a system is at criticality [3,4,5,6,7,8,9]. On the other hand, fidelity, another basic notion in quantum information science, has demonstrated to be fundamental in characterizing phase transitions in quantum many-body systems [10,11,12,13]. This adds a new routine to explore quantum criticality in condensed matter physics from a quantum information perspective.However, with only a few notable exceptions [14,15], not much work has been done for two-dimensional (2D) quantum systems, due to great computational challenges. In fact, despite the existence of well-established numerical algorithms, such as exact diagonalization, quantum Monte Carlo (QMC), the density matrix renormalization group (DMRG) and series expansions, drawbacks become obvious when one deals with frustrated spin systems. A typical example is the QMC, which suffers from the notorious sign problem. However, a promising progress, inspired by new concepts from quantum information science, has been made in classical simulations of quantum many-body systems. The algorithms are based on an efficient representation of the system's wave functions through a tensor network. In particular, matrix product states (MPS) [16,17,18], a tensor network already present in DMRG, are used in the time-evolving block decimation (TEBD) algorithm to simulate time evolution in 1D quantum lattice systems [19,20], whereas projected entangled-pair states (PEPS) constitute the basis to simulate 2D quantum lattice systems [21,22].The aim of this paper is to show that the fidelity per lattice site, first introduced in Ref. [11], is able to unveil quantum criticalit...

Objective To summarize the clinical characteristics of adult cases of paragonimiasis with lung masses as the main manifestation in Xishuangbanna, Yunnan Province, analyze the causes of misdiagnosis, and improve the levels of clinical diagnosis and treatment. Method We conducted a retrospective analysis of the clinical data and diagnosis and treatment of 8 adult cases of paragonimiasis with lung masses as the main manifestation that were diagnosed in the Oncology Department of People’s hospital of Xishuangbanna Dai Autonomous Prefecture from July 2014 to July 2019. Result All 8 patients were from epidemic paragonimiasis areas and had a confirmed history of consuming uncooked freshwater crabs. The clinical manifestations were mainly fever, dry cough, and chest pain. The disease durations were long, and peripheral blood eosinophil counts were elevated. The cases had been misdiagnosed as pneumonia or pulmonary tuberculosis. After years of anti-inflammatory or anti-tuberculosis treatment, the symptoms had not improved significantly. Patients eventually sought treatment from the oncology department for hemoptysis. Chest computed tomography showed patchy consolidation in the lungs, with nodules, lung masses, and enlarged mediastinal lymph nodes. Conclusion Paragonimiasis is a food-borne parasitic disease. Early clinical manifestations and auxiliary examination results are nonspecific. The parasite most often invades the lungs, and the resulting disease is often misdiagnosed as pneumonia, pulmonary tuberculosis, or lung cancer (Acta Trop 199: 05074, 2019). To avoid misdiagnosis, clinicians should inquire, in detail, about residence history and history of unclean food and exposure to infected water and make an early diagnosis based on the inquired information and imaging examination results. For patients who have been diagnosed with pneumonia or pulmonary tuberculosis and whose symptoms do not improve significantly after anti-inflammatory or anti-tuberculosis treatments, their epidemiological history should be traced to further conduct differential diagnosis and avoid misdiagnosis.