AtMol Research Seminar Archive
Index Current Seminars

Unless otherwise advertised, all talks are in room Ph30 at 1:00pm on Wednesdays.

Epiphany Term 2014

Date Speaker Institution
Journal Club - The physics of atomic bombs
Wed 22 Jan 2014 Peter Molony Durham University

The design of nuclear and thermonuclear bombs is extremely complex, involving a range of physical and technical challenges. This journal club talk will look at the physical principles of nuclear bombs and the connections to many areas of physics including particle theory, diffusion theory and optics.

Journal Club - Optomechanics - Quantum effects at the meso-scale
Wed 29 Jan 2014 Chris Wade Durham University

Optomechanical systems couple light to mechanical oscillators with the goal of observing quantum mechanical effects. In the last four years this field has taken flight, with observations of a mechanical oscillator cooled to the quantum ground state [1], Opto-Mechanically Induced Transparency [2] (a close analogue of the familiar Electromagnetically Induced Transparency) and coherent state transfer [3]. In this talk we will consider the physical principles of optomechanics and review some of the recent advances"

[1] J. Chan et al. Nature 478 89 (2011)
[2] S. Weis et al. Science 330 1520 (2010)
[3] T. Palomaki et al. Nature 495 210 (2013)

Dynamics of blockaded Rydberg gases in low dimensions
Wed 5 Feb 2014 Guido Pupillo Université de Strasbourg

We discuss the quantum phases and dynamics of a gas of two-dimensional Bosons with finite-range soft-core interactions. For low densities, the system is shown to form a solid in which superfluidity is provided by delocalized zero-point defects. This provides the first example of continuous-space supersolidity consistent with the Andreev-Lifshitz-Chester scenario. We further discuss the connection between quantum mechanical supersolid behaviour and a novel mechanism for a glass formation.

Towards quantum telescopes – Can Quantum Optics serve astronomy?
Wed 12 Feb 2014 Aglaé Kellerer Durham University

Today's telescopes still rely on the classic processes of light diffraction and interference. But this will change and intensity interferometry, developed by Hanburry-Brown and Twiss, can already be cited as an exception. Since intensity interferometry was first proposed in the 1960s, quantum optics has made substantial progress and the future of astronomy may well depend on the use of novel quantum optical mechanisms.

As the challenges associated with building ever larger telescopes increase, processes such as stimulated emission, quantum entanglement and quantum non-demolition measurements will offer possibilities well worth to be explored. I will examine the possibility of overcoming the diffraction limit of a telescope through photon cloning processes heralded by trigger signals (http://dx.doi.org/10.1051/0004-6361/201322665). The feasibility of the proposed scheme is still uncertain, but as the technology advances and new ideas come forward the set-up may be sufficiently expanded and modified to become practicable.

The main message of this seminar will be the possibility in principle to improve the angular resolution of a telescope beyond the diffraction limit, and thus to achieve high-angular resolutions even with moderately sized telescopes The intention is to motivate a broad discussion that includes similar and perhaps more viable approaches.

Our recent work on Fermi mixtures
Wed 19 Feb 2014 Zhihao Lan Southampton University

In this talk I will show you our recent work on Fermi mixtures, which will have two parts. In the first part, and also the main focus of this talk, I will show you how, by bringing in knowledge from few-body physics, we can extend the traditional Hubbard model. In particular, we trap one species in an optical lattice while another species untrapped but has an s-wave bound state with the first species so is essentially trapped. When the scattering length is large on the order of the lattice spacing, the orbitals of the untrapped species overlap and form a band. We illustrate this idea by implementing an electron-phonon quantum simulator which shows strong renormalization of phonon frequencies due to electron-phonon interaction and lattice dimerization due to Peierls instability. In the second part, I will briefly discuss the novel Fermi liquid behaviors in Fermi mixtures with density and mass imbalances, where the quasiparticle lifetimes no longer show quadratic dependence on energy and temperature as in traditional Landau Fermi liquids, but rather can have exotic linear or even constant dependence on energy or temperature, which will have crucial effects on the transport properties of system.

References:
Part I: arXiv:1310.4152.
Part II: Phys.Rev.Lett.111,145301(2013).

Correlations and spatial structures in ultracold Rydberg gases
Tues 25 Feb 2014 Servaas Kokkelmans Technical University of Eindhoven

Crystalline structures of highly excited Rydberg atoms can be a model for dilute metallic solids with tunable parameters, and provide access to the regime of strongly coupled systems. In practice, crystal creation is made difficult by the 'Rydberg blockade', where one atom in the Rydberg state shifts the energy levels of its neighbours out of resonance with the excitation laser.

In our experiment, we can spatially detect Rydberg atoms by a combination of field-ionization, and subsequent acceleration of the remaining ions onto a multi-channel plate. In this way, we were able to determine the blockade radius from measuring second-order correlations. We have also made small ordered Rydberg structures by optically imprinting local excitations in a disordered atomic gas using a spatial light modulator. With this diffractive optical element it is possible to control the intensity of light in the far field and create almost any desired intensity pattern.

We found that a Rydberg system with a dissipative mechanism can be mapped onto a set of rate equations that describe a wireless computer network. In these networks neighbouring transmitters have a similar blockade effect on each other. For the Rydberg system, we used mathematical tools developed for wireless networks, and applied this to optically imprinted square lattices.

Ultracold charged particle sources
Wed 26 Feb 2014 Edgar Vredenbregt Technical University of Eindhoven

Ultracold plasmas are produced by near-threshold photoionization of laser-cooled and trapped atoms. In turn, these plasmas are a novel source of electron and ion beams that for instance provide a route to achieving high brightness from an extended source due to the low temperature. Application of such ultracold beams in focused ion beam instruments is actively being pursued. Here, reducing disorder-induced heating and achieving low energy spread lead to competing demands in order to optimize focal spot size. In electron diffraction, cold sources allow for ultrashort pulses of substantial charge with relatively large coherence length. Our ultimate goal is to apply these to studies of the structural dynamics of macromolecules.

SEMINAR CANCELLED
Wed 5 Mar 2014 Yuri Pashkin Lancaster University

Abstract TBC

SEMINAR CANCELLED
Wed 12 Mar 2014 Silvia Bergamini Open University

Abstract TBC

What comes next for Particle Physics?
Wed 19 Mar 2014 Nigel Glover Durham University

This talk addresses the current status of particle physics and aims to answer questions such as Where are we now? What is special about the Higgs? What questions remain to be answered? How are we going to answer them?

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