scholarly journals Exceptional points in oligomer chains

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Charles Andrew Downing ◽  
Vasil Arkadievich Saroka
Keyword(s):  
Open Systems ◽  
Light Transport ◽  
Coupled Modes ◽  
Exceptional Points ◽  
Time Symmetry ◽  
Degree Of Coherence ◽  
Quantum Objects ◽  
Long Range Interactions ◽  
And Control ◽  
Symmetric Systems

AbstractSymmetry underpins our understanding of physical law. Open systems, those in contact with their environment, can provide a platform to explore parity-time symmetry. While classical parity-time symmetric systems have received a lot of attention, especially because of the associated advances in the generation and control of light, there is much more to be discovered about their quantum counterparts. Here we provide a quantum theory which describes the non-Hermitian physics of chains of coupled modes, which has applications across optics and photonics. We elucidate the origin of the exceptional points which govern the parity-time symmetry, survey their signatures in quantum transport, study their influence for correlations, and account for long-range interactions. We also find how the locations of the exceptional points evolve as a function of the chain length and chain parity, capturing how an arbitrary oligomer chain transitions from its unbroken to broken symmetric phase. Our general results provide perspectives for the experimental detection of parity-time symmetric phases in one-dimensional arrays of quantum objects, with consequences for light transport and its degree of coherence.

scholarly journals Rotation-time symmetry in bosonic systems and the existence of exceptional points in the absence of $${\mathscr{PT}}$$ symmetry

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Ewelina Lange ◽  
Grzegorz Chimczak ◽  
Anna Kowalewska-Kudłaszyk ◽  
Karol Bartkiewicz
Keyword(s):  
Symmetry Breaking ◽  
General Type ◽  
Energy Spectra ◽  
Exceptional Points ◽  
Rotation Time ◽  
Time Symmetry ◽  
Laser Pumping ◽  
Special Cases ◽  
New Applications ◽  
Symmetric Systems

AbstractWe study symmetries of open bosonic systems in the presence of laser pumping. Non-Hermitian Hamiltonians describing these systems can be parity-time ($${{\mathscr{PT}}}$$ PT ) symmetric in special cases only. Systems exhibiting this symmetry are characterised by real-valued energy spectra and can display exceptional points, where a symmetry-breaking transition occurs. We demonstrate that there is a more general type of symmetry, i.e., rotation-time ($${\mathscr{RT}}$$ RT ) symmetry. We observe that $${\mathscr{RT}}$$ RT -symmetric non-Hermitian Hamiltonians exhibit real-valued energy spectra which can be made singular by symmetry breaking. To calculate the spectra of the studied bosonic non-diagonalisable Hamiltonians we apply diagonalisation methods based on bosonic algebra. Finally, we list a versatile set rules allowing to immediately identifying or constructing $${\mathscr{RT}}$$ RT -symmetric Hamiltonians. We believe that our results on the $${\mathscr{RT}}$$ RT -symmetric class of bosonic systems and their spectral singularities can lead to new applications inspired by those of the $${{\mathscr{PT}}}$$ PT -symmetric systems.

Exceptional points in optics and photonics

Science ◽  
2019 ◽  
Vol 363 (6422) ◽  
pp. eaar7709 ◽  
Author(s):  
Mohammad-Ali Miri ◽  
Andrea Alù
Keyword(s):  
Open Systems ◽  
Optical Gain ◽  
Exceptional Point ◽  
Nanoscale Structures ◽  
Exceptional Points ◽  
Time Symmetry ◽  
Applied Technology ◽  
Recent Developments ◽  
Laser Systems ◽  
Distinct Features

Exceptional points are branch point singularities in the parameter space of a system at which two or more eigenvalues, and their corresponding eigenvectors, coalesce and become degenerate. Such peculiar degeneracies are distinct features of non-Hermitian systems, which do not obey conservation laws because they exchange energy with the surrounding environment. Non-Hermiticity has been of great interest in recent years, particularly in connection with the quantum mechanical notion of parity-time symmetry, after the realization that Hamiltonians satisfying this special symmetry can exhibit entirely real spectra. These concepts have become of particular interest in photonics because optical gain and loss can be integrated and controlled with high resolution in nanoscale structures, realizing an ideal playground for non-Hermitian physics, parity-time symmetry, and exceptional points. As we control dissipation and amplification in a nanophotonic system, the emergence of exceptional point singularities dramatically alters their overall response, leading to a range of exotic optical functionalities associated with abrupt phase transitions in the eigenvalue spectrum. These concepts enable ultrasensitive measurements, superior manipulation of the modal content of multimode lasers, and adiabatic control of topological energy transfer for mode and polarization conversion. Non-Hermitian degeneracies have also been exploited in exotic laser systems, new nonlinear optics schemes, and exotic scattering features in open systems. Here we review the opportunities offered by exceptional point physics in photonics, discuss recent developments in theoretical and experimental research based on photonic exceptional points, and examine future opportunities in this area from basic science to applied technology.

MODELLING AND CONTROL OF OPEN SYSTEMS

2016 ◽  
Vol 7 (1) ◽  
pp. 1-19
Author(s):  
Neto José Alves da Silva ◽  
◽  
Giacaglia Giorgio Eugenio Oscare ◽  
Lamas Wendell de Queiroz ◽  
Bargos Fabiano Fernandes ◽  
...  
Keyword(s):  
Open Systems ◽  
And Control

A Software Architecture For Modular Robotic Systems

1994 ◽  
pp. 9-21
Author(s):  
S. Ariffin ◽  
R.H. Weston ◽  
R. Harrison
Keyword(s):  
Control System ◽  
Software Architecture ◽  
Open Systems ◽  
Systems Design ◽  
Robotic Systems ◽  
Reference Architecture ◽  
Real Time Control ◽  
Design Environment ◽  
Machine Control ◽  
And Control

Research is described which is leading to the specification and development of a motion simulation and design environment for modular robotic systems which enables the implementation of widely applicable software processes for machine control. Current investigation is focused on defining models of application tasks in modular robotic systems. This work is based on the Real-time Control System (RCS) reference architecture proposed by researchers at the National Institute of Standards and Technology (NIST) which was designed to support motion planning and implementation. However, this architecture is modified in such a way that it supports the concept of multitasking and inter-process communication. The emphasis of work is on the hierarchical structuring of solutions, this to enable the design and control of distributed motion elements. Also discussed in this paper is a strategy for achieving sensor-based modularization of modular robotic systems in a manner which facilitates fast and efficient response to changes in the functional or environmental requirements. The paper explains how an application software architecture is unified with the open systems design approach known as Universal Machine Control (UMC), which has been devised and developed at Loughborough University to enable reuse to software and control system components.

INTRODUCTION

2012 ◽  
Vol 22 (04) ◽  
pp. 1202002 ◽  
Author(s):  
CHANGPIN LI ◽  
YANG QUAN CHEN ◽  
BLAS M. VINAGRE ◽  
IGOR PODLUBNY
Keyword(s):  
Fractional Calculus ◽  
Scaling Laws ◽  
Power Laws ◽  
Fractional Dynamics ◽  
Long Range Interactions ◽  
Potential Applications ◽  
Dynamics And Control ◽  
Long Memory Processes ◽  
Fractional Differential ◽  
And Control

Fractional Dynamics and Control is emerging as a new hot topic of research which draws tremendous attention and great interest. Although the fractional calculus appeared almost in the same era when the classical (or integer-order) calculus was born, it has recently been found that it can better characterize long-memory processes and materials, anomalous diffusion, long-range interactions, long-term behaviors, power laws, allometric scaling laws, and so on. Complex dynamical evolutions of these fractional differential equation models, as well as their controls, are becoming more and more important due to their potential applications in the real world. This special issue includes one review article and twenty-three regular papers, covering fundamental theories of fractional calculus, dynamics and control of fractional differential systems, and numerical calculation of fractional differential equations.

scholarly journals Observation of non-Bloch parity-time symmetry and exceptional points

2020 ◽  
Author(s):  
Peng Xue ◽  
Lei Xiao ◽  
Tianshu Deng ◽  
Kunkun Wang ◽  
Zhong Wang ◽  
...  
Keyword(s):  
Brillouin Zone ◽  
Skin Effect ◽  
Quantum Walks ◽  
Pt Symmetry ◽  
Great Promise ◽  
Single Photons ◽  
Band Theory ◽  
Exceptional Points ◽  
Time Symmetry ◽  
Transition Points

Abstract Parity-time (PT)-symmetric Hamiltonians have widespread significance in non-Hermitian physics. A PT-symmetric Hamiltonian can exhibit distinct phases with either real or complex eigen spectrum, while the transition points in between, the so-called exceptional points, give rise to a host of critical behaviors that holds great promise for applications. For spatially periodic non-Hermitian systems, PT symmetries are commonly characterized and observed in line with the Bloch band theory, with exceptional points dwelling in the Brillouin zone. Here, in non-unitary quantum walks of single photons, we uncover a novel family of exceptional points beyond this common wisdom. These "non-Bloch exceptional points" originate from the accumulation of bulk eigenstates near boundaries, known as the non-Hermitian skin effect, and inhabit a generalized Brillouin zone. Our finding opens the avenue toward a generalized PT-symmetry framework, and reveals the intriguing interplay among PT symmetry, non-Hermitian skin effect, and non-Hermitian topology.

scholarly journals Asymmetric Rydberg blockade of giant excitons in Cuprous Oxide

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Julian Heckötter ◽  
Valentin Walther ◽  
Stefan Scheel ◽  
Manfred Bayer ◽  
Thomas Pohl ◽  
...  
Keyword(s):  
Cuprous Oxide ◽  
Spatial Correlations ◽  
Many Body ◽  
Molecular Physics ◽  
Oxide Semiconductors ◽  
Pump Probe ◽  
Long Range Interactions ◽  
Atomic And Molecular Physics ◽  
And Control ◽  
Rydberg Blockade

AbstractThe ability to generate and control strong long-range interactions via highly excited electronic states has been the foundation for recent breakthroughs in a host of areas, from atomic and molecular physics to quantum optics and technology. Rydberg excitons provide a promising solid-state realization of such highly excited states, for which record-breaking orbital sizes of up to a micrometer have indeed been observed in cuprous oxide semiconductors. Here, we demonstrate the generation and control of strong exciton interactions in this material by optically producing two distinct quantum states of Rydberg excitons. This is made possible by two-color pump-probe experiments that allow for a detailed probing of the interactions. Our experiments reveal the emergence of strong spatial correlations and an inter-state Rydberg blockade that extends over remarkably large distances of several micrometers. The generated many-body states of semiconductor excitons exhibit universal properties that only depend on the shape of the interaction potential and yield clear evidence for its vastly extended-range and power-law character.

Sign in / Sign up

Export Citation Format

Share Document