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November 2016: Topological pumping of photons in nonlinear resonator arrays

” The inspiration for a new scheme to transport interacting quantum particles has its roots in Ancience Greece. In Thouless pumping, transport happens because of the topology of fields acting on the quantum particles – similar to the way that an Archimedes’ screw pump can move water up a hill,.. ”
Read more from CQT highlight for non specialists ” Topological scheme for transporting quantum particles inspired by Nobel winner’s work “

This work is also highlighted in 7 science news including EurekaAlert!, Phys.org, Health Medicinet, Nanowerk, Nanotechnology Now, Sky Nightly, and Space Daily.

Authors

J. Tangpatinanon, V. M. Bastidas, P. Roushan, S. Assam, D. Jaksch, D. G. Angelakis, “Topological pumping with photons in nonlinear resonator arrays”, Physical Review Letters, 117,  213603 (2016)

Abstract

We show how to implement topological or Thouless pumping of interacting photons in one-dimensional nonlinear resonator arrays by simply modulating the frequency of the resonators periodically in space and time. The interplay between the interactions and the adiabatic modulations enables robust transport of Fock states with few photons per site. We analyze the transport mechanism via an effective analytic model and study its topological properties and its protection to noise. We conclude by a detailed study of an implementation with existing circuit-QED architectures.

Image credit: Embed from Getty Images

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November 2016: Dirac equation in 2-dimensional curved spacetime, particle creation, and coupled waveguide arrays

Authors

C. Koke, C. Noh, D. G. Angelakis, “Dirac equation in 2-dimensional curved spacetime, particle creation, and coupled waveguide arrays”, arXiv:1607.04821,  Annnals of Physics 374, 162 (2016)

Abstract

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.

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September 2016: Semiclassical bifurcations and topological phase transitions in a one-dimensional lattice of coupled Lipkin-Meshkov-Glick models

 Our joint work with Berlin in “Semiclassical bifurcations and topological phase transitions in a one-dimensional lattice of coupled Lipkin-Meshkov-Glick models” has been published in Phys. Rev. E 94, 032123 (2016)

Authors

V. Sorokin, M. Aparicio Alcalde, V. M. Bastidas, G. Engelhardt, D. G. Angelakis, T. Brandes, “Semiclassical bifurcations and topological phase transitions in a one-dimensional lattice of coupled Lipkin-Meshkov-Glick models”, arXiv: 1604.08023, Phys Rev. E. 94, 0321123 (2016)

Abstract

In this work we study a one-dimensional lattice of Lipkin-Meshkov-Glick models with alternating couplings between nearest-neighbors sites, which resembles the Su-Schrieffer-Heeger model. Typical properties of the underlying models are present in our semiclassical-topological hybrid system, allowing us to investigate an interplay between semiclassical bifurcations at mean-field level and topological phases. Our results show that bifurcations of the energy landscape lead to diverse ordered quantum phases. Furthermore, the study of the quantum fluctuations around the mean-field solution reveals the existence of nontrivial topological phases. These are characterized by the emergence of localized states at the edges of a chain with free open-boundary conditions.

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June 2016: The joint COST workshop and school on “Many-Body Physics and Quantum Simulations with Light”

The programme is on! Check out the program, talks (slides and videos) and photos here 

Local Organizing Committee

  • Dimitris G. Angelakis (chair), Technical University of  Crete and Centre for Quantum Technologies, Singapore
  • Jirawat Tangpatinanon, Centre for Quantum Technologies, Singapore
  • Tiang Feng See, Centre for Quantum Technologies, Singapore
  • Nikos Schetakis, Technical University of  Crete

Scientific Advisory Committee

  • Dimitris G. Angelakis, TUC Crete and CQT Singapore (Chair)
  • Darrick Chang, ICFO,  Spain
  • Cristiano Ciuti, Univ. Paris Diderot, France
  • Rosario Fazio, ICTP and NEST, Italy
  • Peter Rabl, TU Vienna,  Austria
  • Atac Imamoglu, ETH, Switzerland

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April 2016: Review on “Quantum Simulations and Many-Body Physics with Light”

Our comprehensive review on “Quantum Simulations and Many-Body Physics with Light” is out at  Reports in Progress in Physics 80, 016401 (2016).

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 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 fibers interfaced with cold atoms.

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February 2016: Beyond mean-field bistability in driven-dissipative lattices: bunching-antibunching transition and quantum simulation

Authors

J. J. Mendoza-Arenas, S. R. Clark, S. Felicetti, G. Romero, E. Solano, D. G. Angelakis, and D. Jaksch “Beyond mean-field bistability in driven-dissipative lattices: Bunching-antibunching transition and quantum simulation”, Phys. Rev. A 93, 023821 (2016)

Abstract

In the present work we investigate the existence of multiple nonequilibrium steady states in a coherently driven XY lattice of dissipative two-level systems. A commonly used mean-field ansatz, in which spatial correlations are neglected, predicts a bistable behavior with a sharp shift between low- and high-density states. In contrast one-dimensional matrix product methods reveal these effects to be artifacts of the mean-field approach, with both disappearing once correlations are taken fully into account. Instead, a bunching-antibunching transition emerges. This indicates that alternative approaches should be considered for higher spatial dimensions, where classical simulations are currently infeasible. Thus we propose a circuit QED quantum simulator implementable with current technology to enable an experimental investigation of the model considered.

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November 2015: Few Photon Transport in Many-Body Photonic Systems: A Scattering Approach

With the help of two-photon scattering matrix of in- and out-states, we find that the use of quantum input states in photonic quantum simulators such as those implemented in coupled cavity arrays, allows one to observe not only stronger spectroscopic signals of the underlying strongly correlated states but also a faithful representation of their intensity-intensity correlations, as compared to the conventional classical driving fields. Our analysis can be applied for many-body spectroscopy of any many-body model amenable to a photonic quantum simulation,  including the Jaynes-Cummings-Hubbard, the extended Bose-Hubbard, and a whole range of spin models.

Authors

C. Lee, C. Noh, N. Schetakis,  D. G. Angelakis “Few photon transport in nonlinear cavity arrays:Probing signatures of strongly correlated states”, Phys. Rev. A 92, 063817 (2015).

Abstracts

We study the quantum transport of multiphoton Fock states in one-dimensional Bose-Hubbard lattices implemented in QED cavity arrays (QCAs). We propose an optical scheme to probe the underlying many-body states of the system by analyzing the properties of the transmitted light using scattering theory. To this end, we employ the Lippmann-Schwinger formalism within which an analytical form of the scattering matrix can be found. The latter is evaluated explicitly for the two-particle, two-site case which we use to study the resonance properties of two-photon scattering, as well as the scattering probabilities and the second-order intensity correlations of the transmitted light. The results indicate that the underlying structure of the many-body states of the model in question can be directly inferred from the physical properties of the transported photons in its QCA realization. We find that a fully resonant two-photon scattering scenario allows a faithful characterization of the underlying many-body states, unlike in the coherent driving scenario usually employed in quantum master-equation treatments. The effects of losses in the cavities, as well as the incoming photons’ pulse shapes and initial correlations, are studied and analyzed. Our method is general and can be applied to probe the structure of any many-body bosonic model amenable to a QCA implementation, including the Jaynes-Cummings-Hubbard model, the extended Bose-Hubbard model, as well as a whole range of spin models.

 

 

 

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July 2015: Quantum plasmonic excitation in graphene and loss-insensitive propagation

Authors:

G. W. Hanson, S. A. H. Gangaraj, C. Lee, D. G. Angelakis, M. Tame “Quantum plasmonic excitation in graphene and robust-to-loss propagation”, Phys. Rev. 92, 013828 (2015)

Abstract:

We investigate the excitation of quantum plasmonic states of light in graphene using end-fire and prism coupling. In order to model the excitation process quantum mechanically, we quantize the transverse-electric and transverse-magnetic surface plasmon polariton (SPP) modes in graphene. A selection of regimes are then studied that enable the excitation of SPPs by photons and we show that efficient coupling of photons to graphene SPPs is possible at the quantum level. Furthermore, we study the excitation of quantum states and their propagation under the effects of loss induced from the electronic degrees of freedom in the graphene. Here we investigate whether it is possible to protect quantum information using quantum-error correction techniques. We find that these techniques provide a robust-to-loss method for transferring quantum states of light in graphene over large distances.

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April 2015: Optical simulation of charge conservation violation and Majorana dynamics

“Forbidden physics has been seen in an experiment – sort of. CQT researchers and collaborators in Germany, Austria and India simulated with light the behaviour of an impossible particle known as a Majoranon…”
Read more from CQT highlight for non specialists, ” Light mimics forbidden particle “

This work was chosen for a focus article in Οptics & Photonics News (OPN)  “Using light to simulate unphysical particles”. ! It has also appeared in the Science Section, International Business Times, as well as phys.org  and sciencedaily

Authors

R. Keil, C. Noh, A. Rai, S. Stutzer, S. Nolte, D. G. Angelakis, A. Szameit “Experimental simulation of charge conservation violation and Majorana dynamics”, Optica 2,454 (2015)

Abstracts

Unphysical solutions are ruled out in physical equations, as they lead to behavior that violates fundamental physical laws. One of the celebrated equations that allows unphysical solutions is the relativistic Majorana equation, thought to describe neutrinos and other exotic particles predicted in theories beyond the standard model. The neutrally charged Majorana fermion is the equation’s physical solution, whereas the charged version is, due to charge nonconservation, unphysical and cannot exist. Here, we present an experimental scheme simulating the dynamics of a charged Majorana particle by light propagation in a tailored waveguide chip. Specifically, we simulate the free-particle evolution as well as the unphysical operation of charge conjugation. We do this by exploiting the fact that the wave function is not a directly observable physical quantity and by decomposing the unphysical solution to observable entities. Our results illustrate the potential of investigating theories beyond the standard model in a compact laboratory setting.