The Queen's
University of Belfast **|**
School of Maths
& Physics **|**
Theor. &
Comput. Physics
## Theoretical Atomic, Molecular and Optical Physics

# SEMINARS

(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
g.gribakin@am.qub.ac.uk

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).

You may email comments about this page to
g.gribakin@am.qub.ac.uk