Photon waiting time distributions: a keyhole into dissipative quantum chaos

Open quantum systems can exhibit complex states, which classification and quantification is still not well resolved. The Kerr-nonlinear cavity, periodically modulated in time by coherent pumping of the intra-cavity photonic mode, is one of the examples. Unraveling the corresponding Markovian master equation into an ensemble of quantum trajectories and employing the recently proposed calculation of quantum Lyapunov exponents [I.I. Yusipov {\it et al.}, Chaos {\bf 29}, 063130 (2019)], we identify `chaotic' and `regular' regimes there. In particular, we show that chaotic regimes manifest an intermediate power-law asymptotics in the distribution of photon waiting times. This distribution can be retrieved by monitoring photon emission with a single-photon detector, so that chaotic and regular states can be discriminated without disturbing the intra-cavity dynamics.Comment: 7 pages, 5 figure

Control of a single-particle localization in open quantum systems

We investigate the possibility to control localization properties of the asymptotic state of an open quantum system with a tunable synthetic dissipation. The control mechanism relies on the matching between properties of dissipative operators, acting on neighboring sites and specified by a single control parameter, and the spatial phase structure of eigenstates of the system Hamiltonian. As a result, the latter coincide (or near coincide) with the dark states of the operators. In a disorder-free Hamiltonian with a flat band, one can either obtain a localized asymptotic state or populate whole flat and/or dispersive bands, depending on the value of the control parameter. In a disordered Anderson system, the asymptotic state can be localized anywhere in the spectrum of the Hamiltonian. The dissipative control is robust with respect to an additional local dephasing.Comment: 6 pages, 5 figure

Localization in open quantum systems

In an isolated single-particle quantum system a spatial disorder can induce Anderson localization. Being a result of interference, this phenomenon is expected to be fragile in the face of dissipation. Here we show that dissipation can drive a disordered system into a steady state with tunable localization properties. This can be achieved with a set of identical dissipative operators, each one acting non-trivially only on a pair of neighboring sites. Operators are parametrized by a uniform phase, which controls selection of Anderson modes contributing to the state. On the microscopic level, quantum trajectories of a system in a localized steady regime exhibit intermittent dynamics consisting of long-time sticking events near selected modes interrupted by jumps between them.Comment: 5 pages, 5 figure

Addressing the needs of international students: a case from a russian university

Introduction The study addresses the needs of university educators in alternative, more efficient teaching techniques supported by the psychological approach.Method The introduced method of fairy tale writing, based on the potential of Russian traditional fairy tales, encourages critical thinking, and enhances the problem solving process in the context of international students’ identification with an imaginary personality. The defense mechanisms unconsciously applied in the frame of an individual’s narration assist in interpreting their emotional state and psychological adaptation levels at a certain point in time.Results The complexity of the adjustment process should be scrupulously considered, as the nature of individually applied defense mechanisms is dependent on the culture and contextually relevant. Fairy tale therapy gives international students a chance to negotiate identity in writing and acquire positive feelings of attachment and belonging. Instructors benefit from “hearing out” and learning about the students who, in the traditional educational setting, would reveal shyness associated with some cultural predisposition (China, Japan, and Korea).Discussion The timely changed class instruction style and more person-centered approach can modify the situational adaptation outcomes, and long-duration observation can provide aclearer picture of identity transition. Arrangements should be made to adequately shift emotional discontent at the critical point, and this is a task for both the local university administration and the national legislative body. The theoretical prerequisite of universalism of human emotions enables the educators to perceive the coded message in the narrators’ ‘voices’ and become mediators between international students and university administration.Keywords: defense mechanisms, emotional state, psychological adaptation, Russian fairy tales, universal semantic primitive

Lyapunov exponents of quantum trajectories beyond continuous measurements

Quantum systems interacting with their environments can exhibit complex non-equilibrium states that are tempting to be interpreted as quantum analogs of chaotic attractors. Yet, despite many attempts, the toolbox for quantifying dissipative quantum chaos remains very limited. In particular, quantum generalizations of Lyapunov exponent, the main quantifier of classical chaos, are established only within the framework of continuous measurements. We propose an alternative generalization which is based on the unraveling of a quantum master equation into an ensemble of so-called 'quantum jump' trajectories. These trajectories are not only a theoretical tool but a part of the experimental reality in the case of quantum optics. We illustrate the idea by using a periodically modulated open quantum dimer and uncover the transition to quantum chaos matched by the period-doubling route in the classical limit.Comment: 5 pages, 4 figure

Localization in periodically modulated speckle potentials

Disorder in a 1D quantum lattice induces Anderson localization of the eigenstates and drastically alters transport properties of the lattice. In the original Anderson model, the addition of a periodic driving increases, in a certain range of the driving's frequency and amplitude, localization length of the appearing Floquet eigenstates. We go beyond the uncorrelated disorder case and address the experimentally relevant situation when spatial correlations are present in the lattice potential. Their presence induces the creation of an effective mobility edge in the energy spectrum of the system. We find that a slow driving leads to resonant hybridization of the Floquet states, by increasing both the participation numbers and effective widths of the states in the strongly localized band and decreasing values of these characteristics for the states in the quasi-extended band. Strong driving homogenizes the bands, so that the Floquet states loose compactness and tend to be spatially smeared. In the basis of the stationary Hamiltonian, these states retain localization in terms of participation number but become de-localized and spectrum-wide in term of their effective widths. Signatures of thermalization are also observed.Comment: 6 pages, 3 figure

Improving Bacillus Altitudinis B-388 Genome Scaffolding Using Mate-Pair Next-Generation Sequencing

© 2016, Springer Science+Business Media New York.Bacillus species, generally regarded as soil microorganisms, are present in human gastrointestinal tract (GIT) in quantities, which cannot be explained by their entrance with food only. They are capable of growing in GIT and interacting with intestinal microbiota and host organism by excretion of enzymes and low-molecular weight compounds, which exert digestion-facilitating, antagonistic, immunomodulating, antiviral, anticancer properties or mediate cell communication. For better understanding of its probiotic potential, we have sequenced genome of Bacillus altitudinis B-388 using mate-pair technology. It allowed us to improve quality of the genome sequence. The number of contigs decreased from 59 to 8. N50 contig length increased by four times. The number of identified genes raised from 3730 to 3774 (3645 proteins and 73 RNAs) with the reduction of frameshifted genes. The calculated size of B. altitudinis B-388 genome is 3,743,699 bp, with a G + C content of 41.17 mol%. Additional incomplete prophage sequence in genome of B. altitudinis B-388 was revealed. It was found that cryptic plasmid encodes SoxR, an oxidative stress response regulator. To date, the reported sequence is the most thorough presentation of B. altitudinis genome among four whole-genome sequences of this species deposited in GenBank

Biosynthesis of extracellular guanyl-specific ribonuclease by Bacillus circulans

Biosynthesis of extracellular alkaline guanyl-specific RNase by Bacillus circulans (RNase Bci) was studied. Synthesis of the enzyme by the culture started in the late exponential phase and was inhibited by inorganic phosphate and glucose, in contrast to the biosynthesis of its structural and functional homologue, RNase Ba (barnase) of B. amyloliquefaciens. It is suggested that differences in the regulation of the biosynthesis of RNases Bci and Ba are related to different structures of their gene promoters. © 1998 MAHK Hayka/Interperiodica Publishing

Biosynthesis of extracellular guanyl-specific ribonuclease by bacillus circulans

Biosynthesis of extracellular alkaline guanyl-specific RNase by Bacillus circulans (RNase Bei) was studied. Synthesis of the enzyme by the culture started in the late exponential phase and was inhibited by inorganic phosphate and glucose, in contrast to the biosynthesis of its structural and functional homologue, RNase Ba (barnase) of B. amyloliquefaciens. It is suggested that differences in the regulation of the biosynthesis of RNases Bei and Ba are related to different structures of their gene promoters