PREVIOUS COLLOQUIUMS, VISITING LECTURERS & SEMINARS:
Title: Josephson vortices in spin-orbit coupled Bose-Einstein condensates
Presented by Antonio Munoz, Massey University
When: Date: Friday 17 March, 12 noon (sharp) to 1.00pm
We have analyzed the dynamics of planar solitons in two-component Bose-Einstein condensates with Rashba-Dresselhaus spin-orbit coupling within the framework of the Gross-Pitaevskii equation. In particular, we have focused on Josephson vortex (JV) states, which share features with fluxons in superconducting long Josephson junctions. Such supercurrent states, made of solitons in each condensate component, are arranged so that the relative phase jumps an integer multiple of $2pi$. We have found stable JVs in multidimensional systems within a regime of parameters typical of current experiments. Above an interaction threshold, and in oblate condensates, we have reported on how JVs can decay through the snake instability into vortex dipoles, whose motion is guided by the spin-orbit coupling. These configurations provide an excellent playground to observe the rich dynamics of planar solitons and vortex dipoles in spinor condensates as has been previously done in scalar Bose-Einstein condensates through other states.
Title: Towards non-contacting measurements of the elastic properties of rocks under in situ conditions
When: Date: Friday 10 March
The elastic properties of rocks are of interest to a wide range of geophysicists. Whether you exploit a geothermal field, or worry about the hazards of faults and volcanoes, rock physics plays an important role in geophysical applications. In the lab, we aim to understand the effects of fluid content and rock alteration, and to calibrate field observations. The expertise in the Dodd-Walls Centre allows us to exploit the advantages of laser-based experimentation, and here I will present new developments towards rock physics measurements under in situ conditions.
Title: Dissipative Phases of Cavity-Mediated Photon Interactions
presented by Dodd-Walls Centre and University of Auckland, Ricardo Gutierrez Jauregui
When: Friday 24 February 2017
The exquisite control acquired over quantum systems in recent years has provided a playground for studies of transitions between different phases of light and matter[1;2]. The realization of the Bose-Einstein condensate opened the door for quantum optics experiments using matter waves, while the advent of circuit quantum electrodynamics has allowed for strongly interacting systems to be simulated by light fields. However, due to dissipation, the duality between light and matter systems is not complete. Dissipation affects both the evolution and the physical properties of a quantum system in a fundamental way.
In this seminar we address the question of how phase transitions in equilibrium relate to their driven dissipative analogues. This is done by contrasting the phases acquired by a quasi-conservative system, interacting BEC in an optical trap, with a driven-dissipative system, two driven cavities presenting a Kerr nonlinearity. We present the phases the system can acquire in both scenarios. First, for the single cavity limit where tunnelling is suppressed, then for the full Hamiltonian where competition of J and g leads to different phases of the system. The effect of quantum fluctuations on the phases of the system is highlighted.
 M. Greiner, O. Mandel, T. Esslinger, T. W. Hansch, I. Bloch, Nature 415, 39 (2002).
 A. D. Greentree, C. Tahan, J. H. Cole, and L. C. L. Hollenberg, Nature Physics 2, 856 (2006).
 G. Kirchmair, B. Vlastakis, Z. Leghtas, S. E. Nigg, H. Paik, E. Ginossar, M. Mirrahimi, Lu. Frunzio, S. M. Girvin
& R. J. Schoelkopf, Nature 495, 205209 (2013).
Title: Intermittent Many-Body Dynamics at Equilibrium
presented by Dodd-Walls Centre and Massey University, Professor Sergej Flach Institute for Basic Science, Daejeon
When: Friday 17 February 2017
The equilibrium value of an observable defines a manifold in the phase space of an ergodic and equipartitioned many-body system. A typical trajectory pierces that manifold infinitely often as time goes to infinity. We use these piercings to measure both the relaxation time of the lowest frequency eigenmode of the Fermi-Pasta-Ulam chain, as well as the fluctuations of the subsequent dynamics in equilibrium. We show that previously obtained scaling laws for equipartition times are modified at low energy density due to an unexpected slowing down of the relaxation. The dynamics in equilibrium is characterized by a power-law distribution of excursion times far off equilibrium, with diverging variance. The long excursions arise from sticky dynamics close to regular orbits in the phase space. Our method is generalizable to large classes of many-body systems.
Title: From Open Quantum Walks to Open Quantum Brownian Motion
The Dodd-Walls Centre together with the University of Auckland would like to welcome visiting Professor Francesco Petruccione of the University of KwaZulu-Natal.
When: Wednesday 14 December 2016
Title: Accurate and efficient analytical and numerical methods for electromagnetic scattering
presented by Dodd-Walls Centre and Victoria University of Wellington, Professor Eric Le Ru
When: Thursday 15 December 2016
Title: Nonclassicality in Quantum Optics: Phase-Space Approach
The Dodd-Walls Centre together with the University of Auckland and the QFG SuperGroup would like to welcome visiting Professor Hyunchul Nha of Texas A&M University at Qatar.
When: Friday 16 December 2016
Title: Scattering Theory for Experimentalist
presented by Dodd-Walls Centre and the Department of Physics at the University of Otago, Ryan Thomas
When: Friday 18 November 2016
Title: Practical Quantum Metrology in Noisy Environments presented by Rosanna Nichols of the University of Nottingham
When: Tuesday 15 November
Title: Quantum dark solitons in the leib-liniger model as localised wavepackets of type-ii excitations
presented by Dodd-Walls Centre and Massey University, Sophie Shamailov
Title: Topological Photonics
Presented by Professor Alexander Szameit from the Institute of Applied Physics, Universität Jena, Germany. Distinguished Guest to the University of Auckland
When: Friday 28 October 2016
Read full abstract here
Title: small refractive index, high performance: mgf2 wgm resonators for refractometric sensing and more..
presented by the Dodd-Walls Centre and The Department of Physics at the University of Otago, Harald Schwefel
When: Friday 14 October 2016
I will present our experimental results on refractrometric sensing with crystalline, birefringent ultra-high q mgf2 whispering gallery mode resonators. Such resonators have a refractive index that is very close to that of water, thus the evanescent field present on the surface of the resonators can penetrate deep into the surrounding medium. This provides a high sensitivity towards changes in the refractive index of the surrounding. We measured a bulk index sensitivity of 3.26 nm per riu in a millimeter sized resonator and found q-factors of more than 108 in aqueous environments. I will give also an outlook on other sensing directions with thz radiation as well as biological and chemical interactions that i intend to investigate within the framework of resonant optics.
Title: Crystal-Field Modelling of Hyperfine Structure for Low Symmetry Rare-Earth Doped Insulators
presented by the Dodd-Walls Centre postdoctoral fellow from the Department of Physics at the University of Otago, Sebastian Horvath.
When: Friday 23rd September 2016
Title: Quantum Computing 2.0: The Next Generation
The DWC and The QFG Supergroup sponsored A Colloquium taken by Professor Peter Drummond, Science Director Of The Centre For Quantum And Optical Science At Swinburne University Of Technology In Melbourne
When: Friday 16th September 2016
Title: Spectroscopy of New Zealand Lamb Meat: A Preliminary Analysis
presented by Dodd-Walls Centre PhD Candidate from the Department of Chemistry at the University of Otago, Ruth Sales.
When: Friday 9th September 2016
Title: Thermalisation of a Bose Gas in a Harmonic Trap
presented by Dodd-Walls Centre PhD Candidate from the Department of Physics at the University of Auckland, Dylan Brown.
When: Friday 19th August 2016
We present recent measurements, where we excite 50% of the atoms from a BEC in a harmonic trap to a state with $2hbar k$ of momentum. This component will oscillate in the trap, and collide with the remaining BEC multiple times. We observe thermalisation of the cloud to a new equilibrium, which might include a new BEC oscillating in the trap.
Title: How hot are negative absolute temperatures? The case of the Bose-Einstein superfluid
Presented by Professor Gian-Luca Oppo, University of Strathclyde - Distinguished Visitor to Department of Physics, University of Auckland
When: Friday 19th August 2016
Temperature is one of the physics concepts that we all believe to be easy to understand. After all there are thermometers measuring temperatures almost everywhere on earth. Understanding temperature when the physical system under consideration has more conserved quantities than just the total energy is however all but trivial. In this case, the normal kinetic temperature associated to the high speed of molecules in a gas does not work. By introducing micro-canonical temperatures, we find that it is possible to reach infinite values of the temperature and even pass it to move to negative temperatures that are above infinity.
This topic is so hot that there are still major disagreements among scientists (finally resolved in 2015) about the physical reality of negative temperature states. By using the paradigmatic examples of two-level atoms, first, and of a Bose-Einstein condensate in an optical lattice, second, we will see what negative temperatures mean, how to observe them experimentally and what is the disagreement among physicists all about.
Previous public lectures:
Title: The Genius of James CLerk Maxwell, the man who made equations speak
Public Lecture by Professor Gian-Luca Oppo, University of Strathclyde - Distinguished Visitor to Department of Physics, University of Auckland
When: Thursday 18 August 2016
In Einstein’s office in Princeton there were three portraits: Isaac Newton, Michael Faraday and James Clerk Maxwell (1831-1879). Although Maxwell is considered by the academics as one of the most important physicists together with Newton, Galilei, Rutherford, Bohr and, of course, Einstein, his work does not enjoy the same popularity of that of his peers. In his short life, Maxwell has revolutionised the history of science with sensational discoveries: electro-magnetic waves, the speed of light, the unification of electric and magnetic forces, statistical mechanics, the vastness of the electro-magnetic spectrum, light emission, the theory of the thermostat, and even colour photography. While the nineteen century has linked thermodynamics to the industrial revolution, the twentieth century has been dominated by the consequences of Maxwell’s discoveries: the radio, the television, light-matter interactions, x-rays, the radar, the laser, mobile phones, phase transitions, spectroscopy and the internet. Quite an achievement for a shy and reserved Scot. Professor Gian-Luca Oppo is the 1796 Freeland Chair of Natural Philosophy at the University of Strathclyde (Glasgow, Scotland), a Fellow of the Royal Society of Edinburgh, the Optical Society of America, and the Institute of Physics. Professor Oppo is also a recognised teacher and science populariser, and has been awarded the University of Strathclyde Teaching Excellence Awards in 2014 and 2016.