Posted on

Dec 2017-publication in Science: Spectroscopic signatures of localization with interacting photons in superconducting qubits (collaboration with Google-Martinis group)

The international team used photons in Google’s quantum chip to simulate the surprising and beautiful pattern of the ‘Hofstadter butterfly’, a fractal structure characterizing the behaviour of electrons in strong magnetic fields. The results, published 1 December in Science, show how quantum simulators are starting to live up to their promise as powerful tools,…
Read more from CQT highlight for non specialists  ” CQT researchers collaborate in quantum simulations on Google’s superconducting chip” and from USBC highlight ” Simulating physics “

 

This work is highlighted in 12 science news including Strait Time phys.orgeurekalertsciencedailytech2.orghousseniawritingtuc.gr , asian scientist, technology networks, nanowerk, alphagalileo, mgronline 

Science 358, 6367, pp. 1175-1179 (2017)

Authors

P. Roushan, C. Neill, J. Tangpanitanon, V.M. Bastidas, A. Megrant, R. Barends, Y. Chen, Z. Chen, B. Chiaro, A. Dunsworth, A. Fowler, B. Foxen, E. Je rey, J. Kelly, E. Lucero, J. Mutus, M. Neeley, C. Quintana, D. Sank, A. Vainsencher, J. Wenner, T. White, H. Neven, D. G. Angelakis, and J. Martinis

Abstracts

Quantized eigenenergies and their associated wave functions provide extensive information for predicting the physics of quantum many-body systems. Using a chain of nine superconducting qubits, we implement a technique for resolving the energy levels of interacting photons. We benchmark this method by capturing the main features of the intricate energy spectrum predicted for two-dimensional electrons in a magnetic field—the Hofstadter butterfly. We introduce disorder to study the statistics of the energy levels of the system as it undergoes the transition from a thermalized to a localized phase. Our work introduces a many-body spectroscopy technique to study quantum phases of matter.

Posted on

November 2017: Realizing topological relativistic dynamics with slow light polaritons at room temperature

Authors

M. Namazi, B. Jordaan, C. Noh, D. G. Angelakis, E. Figueroa

Abstract

Here we use a slow light quantum light-matter interface at room temperature to implement an analog simulator of complex relativistic and topological physics. We have realized the famous Jackiw-Rebbi model (JR), the celebrated first example where relativity meets topology. Our system is based upon interacting dark state polaritons (DSP’s) created by storing light in a rubidium vapor using a dual-tripod atomic system. The DSP’s temporal evolution emulates the physics of Dirac spinors and is engineered to follow the JR regime by using a linear magnetic field gradient. We also probe the obtained topologically protected zero-energy mode by analyzing the time correlations between the spinor components. Our implementation paves the way towards quantum simulation of more complex phenomena involving many quantum relativistic particles.

arxiv.org/1711.09346

Posted on

May 2017: Quantum Simulators with Photons and Polaritons: Merging Quantum Optics with Condensed Matter Physics

Check our book on “Quantum Simulators with Photons and Polaritons: Merging Quantum Optics with Condensed Matter Physics” by Springer!

This book reviews progress towards quantum simulators based on photonic and hybrid light-matter systems, covering theoretical proposals and recent experimental work.  Quantum simulators are specially designed quantum computers. Their main aim is to simulate and understand complex and inaccessible quantum many-body phenomena found or predicted in condensed matter physics, materials science and exotic quantum

See CQT highlight for non specialists.

Posted on

May 2017: A diagrammatic Diagrammatic Approach to Multiphoton Scattering

Authors

T.F. See, C. Noh, D.G. Angelakis, “A diagrammatic Diagrammatic Approach to Multiphoton Scattering”, Phys. Rev. A 95, 053845 (2017)

Abstract

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.

Posted on

February 2017: Driven open quantum systems and Floquet stroboscopic dynamics

Dimitris Angelakis (left) and Victor Bastidas (right) with collaborators in Germany found a new way to simplify the equations for a driven quantum system, leading to the discovery that driving can protect a quantum state from decoherence

” Pity poor Schrodinger’s cat. As if it weren’t enough to wish a cat into a state of being simultaneously dead and alive, physicists now have an idea for how to keep it that way – and the answer is to shake it. ….”
Read more from the CQT highlight for non specialists “Shaking Schrodinger’s cat may protect it from the environment”

Authors

Sebastian Restrepo, Javier Cerrillo, V. M. Bastidas, D. G. Angelakis, T. Brandes, “Driven open quantum systems and Floquet stroboscopic dynamics”, Phys. Rev. Lett. 117, 250401 (2016)

Abstract

We provide an analytic solution to the problem of system-bath dynamics under the effect of high- frequency driving that has applications in a large class of settings, such as driven-dissipative many-body systems. Our method relies on discrete symmetries of the system-bath Hamiltonian and provides the time evolution operator of the full system, including bath degrees of freedom, without weak-coupling or Markovian assumptions. An interpretation of the solution in terms of the stroboscopic evolution of a family of observables under the influence of an effective static Hamiltonian is proposed, which constitutes a flexible simulation procedure of nontrivial Hamiltonians. We instantiate the result with the study of the spin-boson model with time-dependent tunneling amplitude. We analyze the class of Hamiltonians that may be stroboscopically accessed for this example and illustrate the dynamics of system and bath degrees of freedom.

 

Posted on

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

Posted on

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.

Posted on

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.

Posted on

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

Posted on

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.