The Queen's University of Belfast | School of Maths & Physics | Theor. & Comput. Physics

Theoretical Atomic, Molecular and Optical Physics


(Seminars in 2000-2007)

These are usually held on Tuesdays at 4.00 pm in room 01.006, new David Bates Building (7 College Park), preceeded by tea/coffee and biscuits in room 01.040 from 3.45 pm.

You are very welcome!

Seminar coordinator Dr G Gribakin

Tuesday, 27 November 2007, 4:00 pm, Lecture Theatre 01.006, David Bates Building

Dr Charles Clark, Joint Quantum Institute, National Institute of Standards and Technology and University of Maryland Gaithersburg, MD 20899, USA

Condensed matter physics at nanograms/cubic centimeter

Ultracold gases confined in optical lattices provide experimentally accessible analogues of important condensed matter systems - even though their densities are typically 100,000 times less than that of air! Optical lattice systems can be produced with a wide range of geometries, and with flexible control of the energies for atomic hopping between lattice sites, and of the on-site atomic interaction energies. Using such pristine model systems, controlled independent-particle phenomena like coherent Bloch oscillations and collective effects like the superfluid-Mott insulator transition, have recently been observed with much greater clarity than has ever been attained in traditional condensed matter physics. This field has just entered an era in which it seems possible to use optical lattices to realize many of the iconic model systems of condensed matter physics - such as the Hubbard model and interacting spin models - and thus perhaps solve some of these computationally intractable models through analogue quantum simulation. Moreover, there are opportunities for synthesizing optical lattice "materials" that manifest many of the exotica of conensed matter physics - skyrmions, anyons, quantum hall states, topologial excitations, Kagome lattices, etc. I will discuss recent studies of the interplay between Anderson and Mott localization in optical lattice systems with disorder, and the construction and application of non-Abelian gauge potentials which yield rich physics beyond the quantum Hall effect.

Tuesday, 6 November 2007

Prof S. Chaturvedi, Institute for Mathematical Sciences, Imperial College London and School of Physics, University of Hyderabad, Hyderabad (India)

Classifying Generalised Wigner distributions in odd dimensions

The question of classifying Generalised Wigner Distributions as defined by Gibbons et al is examined taking eigenvalues of the phase point operators as the basis for categorising them. It is suggested the the relevant group in this context is not the Clifford group, as naively expected, but rather the extended clifford group-- clifford group augmented by  complex conjugation operation. A scheme for mapping phase point operators as elements of a vector space over finite fields is developed and associated representation theoretic aspects are  briefly discussed.

[Work done in collaboration with D. M Appleby and Ingemar Bengtsson]

Tuesday, 30 October 2007

Dr Pieter Kok, Department of Physics and Astronomy, University of Sheffield

Optical quantum computing with photonic and matter qubits

In this talk I will give an overview of optical quantum computing with photons and matter qubits. Whereas in principle it is possible to do scalable quantum computing with only photons, linear optics, and photo-detection, there are huge benefits to using matter qubits with optical transitions. This leads naturally to the use of the one-way model of quantum computing. Recent experiments in Michigan and Paris indicate that this is a feasible route to quantum computing.

Tuesday, 18 September 2007

Alisher Kadyrov, Curtin University of Technology, Perth, Western Australia

Electron-Impact Ionization of Atoms and Problems of Formal Scattering Theory

It is well known that conventional scattering theory is formally valid only when interactions are short-ranged. In the two-body case the theory can be made to include the long-range Coulomb interaction using so-called renormalization methods. However, no renormalization method exists for three charged particles. Attempts to bypass the shortcoming of the general theory in electron-impact ionization lead to introduction of trial quantities like the Peterkop-Rudge integral [M. R. H. Rudge, Rev. Mod. Phys. 40, 564 (1968)]. Formulations based on this integral suffer from a number of problems including an ambiguous and phase-divergent definition of the ionization amplitude. As a first step to a better theory of ionization a formulation of scattering theory for two charged particles without renormalization will be presented. Then an alternative formulation of the ionization theory free of ambiguity and divergence problems will be given.

Tuesday, 11 September 2007

Teodora Baeva, Institute for Theoretical Physics, University of Duesseldorf

High harmonic generation from gases and plasma: between symmetry and universality

The process of high harmonic generation due to the interaction of laser with gasses and plasmas is discussed on the basis of analytical theory and numerical simulations. The properties of the high harmonic radiation in both cases are compared. It is observed that, while the gas harmonics are highly symmetry dependent, the spectrum of the plasma harmonics shows universal features. The origin of this universality is explained within the framework of the theory of relativistic spikes [1].

[1] T. Baeva et. al., Phys. Rev. E 74, 046404 (2006).
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