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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.

 

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.

 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

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