A Floquet Model for the Many-Body Localization Transition

The nature of the dynamical quantum phase transition between the many-body localized (MBL) phase and the thermal phase remains an open question, and one line of attack on this problem is to explore this transition numerically in finite-size systems. To maximize the contrast between the MBL phase and the thermal phase in such finite-size systems, we argue one should choose a Floquet model with no local conservation laws and rapid thermalization to "infinite temperature" in the thermal phase. Here we introduce and explore such a Floquet spin chain model, and show that standard diagnostics of the MBL-to-thermal transition behave well in this model even at modest sizes. We also introduce a physically motivated spacetime correlation function which peaks at the transition in the Floquet model, but is strongly affected by conservation laws in Hamiltonian models

Thermalization of entanglement

We explore the dynamics of the entanglement entropy near equilibrium in highly-entangled pure states of two quantum-chaotic spin chains undergoing unitary time evolution. We examine the relaxation to equilibrium from initial states with either less or more entanglement entropy than the equilibrium value, as well as the dynamics of the spontaneous fluctuations of the entanglement that occur in equilibrium. For the spin chain with a time-independent Hamiltonian and thus an extensive conserved energy, we find slow relaxation of the entanglement entropy near equilibration. Such slow relaxation is absent in a Floquet spin chain with a Hamiltonian that is periodic in time and thus has no local conservation law. Therefore, we argue that slow diffusive energy transport is responsible for the slow relaxation of the entanglement entropy in the Hamiltonian system.Comment: 6 pages, 6 figures; as in journa

Many-body localization phase transition: A simplified strong-randomness approximate renormalization group

We present a simplified strong-randomness renormalization group (RG) that captures some aspects of the many-body localization (MBL) phase transition in generic disordered one-dimensional systems. This RG can be formulated analytically, and the critical fixed point distribution and critical exponents (that satisfy the Chayes inequality) are obtained to numerical precision by solving integro-differential equations. This reproduces many, but not all, of the qualitative features of the MBL phase transition that are suggested by previous numerical work and approximate RG studies: our RG might serve as a "zeroth-order" approximation for future RG studies. One interesting feature that we highlight is that the rare Griffiths regions are fractal. For thermal Griffiths regions within the MBL phase, this feature might be qualitatively correctly captured by our RG. If this is correct beyond our approximations, then these Griffiths effects are stronger than has been previously assumed.Comment: 10 pages, 5 figures; added references; as in journa

Quantum error pre-compensation for quantum noisy channels

Most previous efforts of quantum error correction focused on either extending classical error correction schemes to the quantum regime by performing a perfect correction on a subset of errors, or seeking a recovery operation to maximize the fidelity between a input state and its corresponding output state of a noisy channel. There are few results concerning quantum error pre-compensation. Here we design an error pre-compensated input state for an arbitrary quantum noisy channel and a given target output state. By following a procedure, the required input state, if it exists, can be analytically obtained in single-partite systems. Furthermore, we also present semidefinite programs to numerically obtain the error pre-compensated input states with maximal fidelities between the target state and the output state. The numerical results coincide with the analytical results.Comment: 10 pages, 3 figures

Trajectory Series Analysis based Event Rule Induction for Visual Surveillance

In this paper, a generic rule induction framework based on trajectory series analysis is proposed to learn the event rules. First the trajectories acquired by a tracking system are mapped into a set of primitive events that represent some basic motion patterns of moving object. Then a min-imum description length (MDL) principle based grammar induction algorithm is adopted to infer the meaningful rules from the primitive event series. Compared with previous grammar rule based work on event recognition where the rules are all defined manually, our work aims to learn the event rules automatically. Experiments in a traffic cross-road have demonstrated the effectiveness of our methods. Shown in the experimental results, most of the grammar rules obtained by our algorithm are consistent with the ac-tual traffic events in the crossroad. Furthermore the traffic lights rule in the crossroad can also be leaned correctly with the help of eliminating the irrelevant trajectories. 1

Containment through mobility: migrants’ spatial disobediences and the reshaping of control through the hotspot system

This article deals with the modes of (contested) control that are at play at the Mediterranean frontier for containing, dividing and discipling unruly mobility. Building on ethnographic research conducted on the island of Lesvos and of Lampedusa, it focuses on the implementation and the functioning of the Hotspot System in Greece and in Italy, analysing beyond the fences of detention centres and by looking at the broader logistics of channels, infrastructures and governmental measures deployed for regaining control over migration movements. The article argues that more than control in terms of surveillance and tracking, the Hotspot System contributes to enforce forms of containment through mobility that consists in controlling migration by obstructing, decelerating and troubling migrants’ geographies – more than in fully blocking them. The article takes into account migrants’ refusals of being fingerprinted, showing how migrants radically unsettle the association between seeking refuge and lack of choice, enacting their right to choose where to go and claim asylum

SynFind: Compiling Syntenic Regions across Any Set of Genomes on Demand

The identification of conserved syntenic regions enables discovery of predicted locations for orthologous and homeologous genes, evenwhennosuchgeneispresent.Thiscapabilitymeansthatsynteny-basedmethodsarefarmoreeffectivethansequencesimilaritybased methods in identifying true-negatives, a necessity forstudying gene loss and gene transposition. However, the identification of syntenicregionsrequirescomplexanalyseswhichmustberepeatedforpairwisecomparisonsbetweenanytwospecies.Therefore,as the number of published genomes increases, there is a growing demand for scalable, simple-to-use applications to perform comparative genomic analyses that cater to both gene family studies and genome-scale studies. We implemented SynFind, a web-based tool that addresses this need. Given one query genome, SynFind is capable of identifying conserved syntenic regions in any set of targetgenomes.SynFindiscapableofreportingper-geneinformation,usefulforresearchersstudyingspecificgenefamilies,aswellas genome-wide data sets of syntenic gene and predicted gene locations, critical for researchers focused on large-scale genomic analyses. Inference of syntenic homologs provides the basis for correlation of functional changes around genes of interests between related organisms. Deployed on the CoGe online platform, SynFind is connected to the genomic data from over 15,000 organisms from all domains of life as well as supporting multiple releases of the same organism. SynFind makes use of a powerful job execution framework that promises scalability and reproducibility. SynFind can be accessed at http://genomevolution.org/CoGe/SynFind.pl. A video tutorial of SynFind using Phytophthrora as an example is available at http://www.youtube.com/watch?v=2Agczny9Nyc

Key technologies of TH-2 satellite system

The TH-2 satellite system is the first microwave surveying satellite system based on interferometric synthetic aperture radar (InSAR) technology and the first short-range formation satellite system in China. It is composed of two equal satellites, and the satellites formation in different orbits and the bistatic radar transceiver mode are adopted. By using satellite formations to form the baseline needed for interference, it can measure the global digital surface models by scale of 1∶50 000 in a short time and acquire radar orthophotos at the same time. This paper gives a detailed introduction of the InSAR measurement principle and the technical system of TH-2 is also expounded carefully. To ensure the performance of system and the accuracy of product, several key techniques such as satellite formation, cooperative mode of two satellites, high-precision internal calibration, baseline determination, high-precision baseline measurement, high-precision baseline calibration, imaging of high phase fidelity and absolute ambiguity number calculation using dual-frequency need to be solved. These key technologies are analyzed in this paper, and the solutions are proposed. During the development of the TH-2 satellite system, simulation data and semi-physical simulation test were used to verify the feasibility of the main key technology solutions. After the satellites were launched, the on orbit test showed that the system was operating in good condition and the main performance indicators were better than the designed indicators, which further verified the feasibility of the key technology solutions and the correctness of these methods