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Quantum simulations and many-body physics with light
Noh, Changsuk,Angelakis, Dimitris G The Institute of Physics 2017 Reports on progress in physics Vol.80 No.1
<P>In this review we discuss the works in the area of quantum simulation and many-body physics with light, from the early proposals on equilibrium models to the more recent works in driven dissipative platforms. We start by describing the founding works on Jaynes–Cummings–Hubbard model and the corresponding photon-blockade induced Mott transitions and continue by discussing the proposals to simulate effective spin models and fractional quantum Hall states in coupled resonator arrays (CRAs). We also analyse the recent efforts to study out-of-equilibrium many-body effects using driven CRAs, including the predictions for photon fermionisation and crystallisation in driven rings of CRAs as well as other dynamical and transient phenomena. We try to summarise some of the relatively recent results predicting exotic phases such as super-solidity and Majorana like modes and then shift our attention to developments involving 1D nonlinear slow light setups. There the simulation of strongly correlated phases characterising Tonks–Girardeau gases, Luttinger liquids, and interacting relativistic fermionic models is described. We review the major theory results and also briefly outline recent developments in ongoing experimental efforts involving different platforms in circuit QED, photonic crystals and nanophotonic fibres interfaced with cold atoms.</P>
Dirac equation in 2-dimensional curved spacetime, particle creation, and coupled waveguide arrays
Koke, C.,Noh, C.,Angelakis, D.G. Academic Press 2016 Annals of physics Vol.374 No.-
<P>When quantum fields are coupled to gravitational fields, spontaneous particle creation may occur similarly to when they are coupled to external electromagnetic fields. A gravitational field can be incorporated as a background spacetime if the back-action of matter on the field can be neglected, resulting in modifications of the Dirac or Klein-Gordon equations for elementary fermions and bosons respectively. The semi-classical description predicts particle creation in many situations, including the expanding-universe scenario, near the event horizon of a black hole (the Hawking effect), and an accelerating observer in flat spacetime (the Unruh effect). In this work, we give a pedagogical introduction to the Dirac equation in a general 2D spacetime and show examples of spinor wave packet dynamics in flat and curved background spacetimes. In particular, we cover the phenomenon of particle creation in a time-dependent metric. Photonic analogs of these effects are then proposed, where classical light propagating in an array of coupled waveguides provides a visualisation of the Dirac spinor propagating in a curved 2D spacetime background. The extent to which such a single-particle description can be said to mimic particle creation is discussed. (C) 2016 Elsevier Inc. All rights reserved.</P>
Age of Information Performance of Multiaccess Strategies with Packet Management
Antzela Kosta,Nikolaos Pappas,AnthonyEphremides,Vangelis Angelakis 한국통신학회 2019 Journal of communications and networks Vol.21 No.3
We consider a system consisting of N source nodes communicatingwith a common receiver. Each source node has a bufferof infinite capacity to store incoming bursty traffic in the form ofstatus updates transmitted in packets, which should maintain thestatus information at the receiver fresh. Packets waiting for transmissioncan be discarded to avoid wasting network resources forthe transmission of stale information. We investigate the age of information(AoI) performance of the system under scheduled andrandom access. Moreover, we present analysis of the AoI withand without packet management at the transmission queue of thesource nodes, where as packet management we consider the capabilityto replace unserved packets at the queue whenever newerones arrive. Finally, we provide simulation results that illustratethe impact of the network operating parameters on the age performanceof the different access protocols.
Diagrammatic approach to multiphoton scattering
See, Tian Feng,Noh, Changsuk,Angelakis, Dimitris G. American Physical Society 2017 Physical Review A Vol.95 No.5
<P>We present a method to systematically study multiphoton transmission in one-dimensional systems comprised of correlated quantum emitters coupled to input and output waveguides. Within the Green's function approach of the scattering matrix (S matrix), we develop a diagrammatic technique to analytically obtain the system's scattering amplitudes while at the same time visualize all the possible absorption and emission processes. Our method helps to reduce the significant effort in finding the general response of a many-body bosonic system, particularly the nonlinear response embedded in the Green's functions. We demonstrate our proposal through physically relevant examples involving scattering of multiphoton states from two-level emitters as well as from arrays of correlated Kerr nonlinear resonators in the Bose-Hubbard model.</P>
Secure Communications for the Two-User Broadcast Channel With Random Traffic
Mohapatra, Parthajit,Pappas, Nikolaos,Lee, Jemin,Quek, Tony Q. S.,Angelakis, Vangelis IEEE 2018 IEEE transactions on information forensics and sec Vol.13 No.9
<P>In this paper, we study the stability region of the two-user broadcast channel (BC) with bursty data arrivals and security constraints. It is assumed that one of the receivers has a secrecy constraint, i.e., its packets need to be kept secret from the other receiver, which is defined based on signal to interference noise ratio. The receiver with secrecy constraint has full-duplex capability to send a jamming signal for improving its service rate. The stability region of the two-user BC with secrecy constraint is characterized for the general decoding case. Then, assuming two different decoding schemes, the respective stability regions are derived. The full-duplex operation of receiver results in self-interference, and the effect of imperfect self-interference cancelation on the stability region is also investigated. The stability region of the BC with a secrecy constraint, where the receivers do not have full duplex capability can be obtained as a special case of the results derived in this paper. In addition, the paper considers the problem of maximizing the saturated throughput of the queue for which there is no secrecy constraint under minimum service guarantees for the other queue. The results provide new insights on the effect of the secrecy constraint on the stability region of the BC. It is found that the stability region with secrecy constraint is sensitive to the degree of self-interference cancelation.</P>
Multisetting Greenberger-Horne-Zeilinger theorem
Ryu, Junghee,Lee, Changhyoup,Yin, Zhi,Rahaman, Ramij,Angelakis, Dimitris G.,Lee, Jinhyoung,Ż,ukowski, Marek American Physical Society 2014 Physical review. A. Atomic, molecular, and optical Vol.89 No.2
We present a generalized Greenberger-Horne-Zeilinger (GHZ) theorem, which involves more than two local measurement settings for some parties, and cannot be reduced to one with less settings. Our results hold for an odd number of parties. We use a set of observables, which are incompatible but share a common eigenstate, here a GHZ state. Such observables are called concurrent. The idea is illustrated with an example of a three-qutrit system and then generalized to systems of higher dimensions, and more parties. The GHZ paradoxes can lead to, e.g., secret sharing protocols.
An NADPH-Oxidase/Polyamine Oxidase Feedback Loop Controls Oxidative Burst Under Salinity
Gé,mes, Katalin,Kim, Yu Jung,Park, Ky Young,Moschou, Panagiotis N.,Andronis, Efthimios,Valassaki, Chryssanthi,Roussis, Andreas,Roubelakis-Angelakis, Kalliopi A. American Society of Plant Biologists 2016 Plant Physiology Vol.172 No.3
<P>The apoplastic polyamine oxidase (PAO) catalyzes the oxidation of the higher polyamines spermidine and spermine, contributing to hydrogen peroxide (H2O2) accumulation. However, it is yet unclear whether apoplastic PAO is part of a network that coordinates the accumulation of reactive oxygen species (ROS) under salinity or if it acts independently. Here, we unravel that NADPH oxidase and apoplastic PAO cooperate to control the accumulation of H2O2 and superoxides (O-2(center dot-)) in tobacco (Nicotiana tabacum). To examine to what extent apoplastic PAO constitutes part of a ROS-generating network, we examined ROS accumulation in guard cells of plants overexpressing or down-regulating apoplastic PAO (lines S2.2 and A2, respectively) or down-regulating NADPH oxidase (line AS-NtRbohD/F). The H2O2-specific probe benzene sulfonyl-H2O2 showed that, under salinity, H2O2 increased in S2.2 and decreased in A2 compared with the wild type. Surprisingly, the O-2(center dot-)-specific probe benzene sulfonyl-So showed that O-2(center dot-) levels correlated positively with that of apoplastic PAO (i.e. showed high and low levels in S2.2 and A2, respectively). By using AS-NtRbohD/F lines and a pharmacological approach, we could show that H2O2 and O-2(center dot-) accumulation at the onset of salinity stress was dependent on NADPH oxidase, indicating that NADPH oxidase is upstream of apoplastic PAO. Our results suggest that NADPH oxidase and the apoplastic PAO form a feed-forward ROS amplification loop, which impinges on oxidative state and culminates in the execution of programmed cell death. We propose that the PAO/NADPH oxidase loop is a central hub in the plethora of responses controlling salt stress tolerance, with potential functions extending beyond stress tolerance.</P>
Location of<i>γ</i>-ray emission and magnetic field strengths in OJ 287
Hodgson, J. A.,Krichbaum, T. P.,Marscher, A. P.,Jorstad, S. G.,Rani, B.,Marti-Vidal, I.,Bach, U.,Sanchez, S.,Bremer, M.,Lindqvist, M.,Uunila, M.,Kallunki, J.,Vicente, P.,Fuhrmann, L.,Angelakis, E.,Kar Springer-Verlag 2017 Astronomy and astrophysics Vol.597 No.-