AtMol Research Seminars
Seminar Archive

Michaelmas 2009

Date Speaker Institution
Quantum optics with an atomic vapour: entangled images and quantum memories
14th October Dr. Vincent Boyer University of Birmingham

The entanglement properties of two beams of light can reside in subtle correlations that exist in the unavoidable quantum fluctuations of their amplitudes and phases. I will review recent advances in four-wave mixing in an atomic vapour which have enabled the production and the observation of "entangled images", that is to say beams which are entangled "point per point" across their transverse profiles. These beams can carry quantum information not only in their average profile but also in their spatial details. Moreover, the four-wave mixing process makes it possible to delay the propagation of one of the entangled beams while retaining the quantum correlations, effectively acting as a buffer for quantum images.

Atom chips: Microscopically engineered environments for ultracold gases
21st October Prof. Peter Krüger University of Nottingham

Microfabricating metallic structures onto semiconductor surfaces allows to manipulate cold atoms in complex trapping geometries in the vacuum only microns away from the surface. We will give examples of the wide range of experiments that have already been performed on such atom chips. In particular, we will focus on studies of one-dimensional Bose gases and describe routes to extend these experiments to multiply connected topologies where homogenous one- and two-dimensional systems with periodic boundary conditions can be realized. The proximity of the atoms to the surface can not only be used for high-precision, highly spatially resolved atom manipulation, but the atoms can be exploited as a probe of the surface. We present a proof-of-principle experiment where cold atoms have been used as a microscopic field sensor. An extension of this scheme to semiconductor and magnetic surfaces is outlined with an ultimate goal of forming hybrid atom-surface quantum systems.

28th October Prof. Philippe Grangier Institut d'Optique, Palaiseau

Please note: This seminar will be held in Ph8

This AtMol research seminar will be given by Professor Philippe Grangier of the Institut d'Optique in Orsay, France. Philippe is one of Europe's leading researcher in the field of quantum information. He was involved in the famous experiments lead by Alain Aspect that showed that pairs of photons can be entangled, and has carried out many key experiments in quantum optics, including some of the early experiments on creating squeezed states of light. Today he will talk about his most recent experiments on the creating of entangled pairs of atoms trapped in optical tweezers.

Dynamic manipulation of ultracold atoms using spatial light modulators
4th November Dr Giuseppe Smirne University of St Andrews

The use of a Spatial Light Modulator (SLM) to generate optical traps for ultracold atoms opens the possibility of forming non-periodic patterns of dipole traps to create trapping geometries not achievable using standard techniques. The irregularity of the pattern is an interesting feature because it removes from the observed collective properties of the optically trapped gas features that are due to the periodicity of the lattice. The SLM is an inherently dynamic tool that offers the opportunity to generate smooth, time-varying optical potentials that can in principle be employed to achieve full coherent control over the trapped gas. In this talk I outline the work in progress at St Andrews to achieve novel trapping geometries for Bose-Fermi mixtures using an SLM. I will also describe how we previously demonstrated (in Oxford) the suitability of SLMs in performing dynamic manipulation of a Bose-Einstein condensate.

Advanced Optics to Advance the Life Sciences
11th November Prof. John Girkin University of Durham

The true desire of all life scientists is to obtain three dimensional images, with sub-micron resolution deep within living samples. In the past ten years the advent of non-linear microscopy has brought about a revolution in optical microscopy but as one images more deeply the optical properties of the sample start to distort the image. This is a similar problem to that faced by astronomers and the presentation will discuss and demonstrate how active optical elements can be used to overcome aberrations in optical microscopes. The concept of active locking of optical systems will then be discussed in relation to the removal of sample movement, a serious issue in in vivo imaging applications. The presentation will thus examine several ways in which modern optical technology can be applied to challenges presented in the life sciences demonstrating how by understanding the real challenges physicists' can help to advance life science, and clinical research.

Atomic Ions in Penning Traps for Quantum Information Processing
18th November Dr. D.M. Segal Imperial College

I will describe three recent experiments we have carried out that are relevant to the prospects of doing quantum information processing with atomic ions held in Penning traps. In one experiment we have manipulated and imaged two-ion 'Coulomb crystals' in our trap. In another experiment we have developed a method for rapidly moving ions between different trapping zones in a multiple trap array. Finally, I will discuss an effect due to the magnetic field of the Penning trap that leads to quantum jumps that would otherwise be absent. This latter effect could compromise the fidelity of read-out using atomic ions in Penning traps, but we show that despite the clear effects we see, any reduction of fidelity will be at a tolerable level.

Spatial pattern formation in nonequilibrium condensates
25th November Dr Natalia Berloff University of Cambridge

Quasiparticles in semiconductors - such as microcavity polaritons - can form condensates in which the steady-state density profile is set by the balance of pumping and decay. We model trapped, pumped, decaying condensates by a complex Gross-Pitaevskii equation and analyse the density and currents in the steady state. If the pumping spot is larger than the Thomas-Fermi cloud radius, then rotationally symmetric solutions are replaced by solutions with spontaneous arrays of vortices. These vortex arrays arise without any rotation of the trap, spontaneously breaking rotational symmetry. By taking account of the polarization degree of freedom for such condensates, and considering the effects of an applied magnetic field, I will discuss the interplay between polarization dynamics, and the spatial structure of the pumped decaying condensate.

A trapped single ion inside a Bose-Einstein condensate
2nd December Dr Michael Koehl University of Cambridge

The achievement of excellent control of the motional and the internal quantum states of ultracold neutral atoms and ions has opened intriguing possibilities for quantum simulation and quantum computation. In quantum degenerate neutral atoms many-body effects have been explored with hundreds of thousands of atoms and coherent light-matter interfaces have been built. Single or few trapped ions have been employed to demonstrate universal quantum computing algorithms and to detect variations of fundamental constants in precision atomic clocks. Until now quantum gases and single trapped ions have been disconnected in experiments. Their complementarities suggest, however, that they could be advantageously combined into one hybrid system. We have explored the immersion of a single trapped ion into a Bose-Einstein condensate of neutral atoms. We demonstrate the full independent control over the two systems, study the fundamental interaction processes, and observe sympathetic cooling of a single ion by immersion into a Bose-Einstein condensate. Our experiment opens possibilities for continuous cooling of a quantum computer and for exploring entanglement in hybrid quantum systems.

The Fermi Polaron Problem
9th December Dr. Carlos Lobo University of Southampton

An impurity propagating in a medium can sometimes be thought of as a "dressed" particle (a quasiparticle) where its properties are changed from those it has in the vacuum. This idea goes back to the 1930s where in high energy physics and in condensed matter it was explored indifferent contexts. In Fermionic atomic gases this physics also emerges and we can study it with great depth and precision. I will explain the basic ideas and discuss the recent theoretical and experimental developments.

Search for New Physics at Low Energies
16th December Dr Joerg Jaeckel University of Durham

Particle physics is often associated with huge experiments like the LHC which explore the high energy frontier. However, small scale, low energy but high precision experiments can provide a wealth of complementary information on the fundamental laws of nature. In this talk we will look at why it is likely that there is physics beyond the current standard model and how it can be explored in low energy experiments and observations.

Room Bookings for Ph30 are made by contacting Ian Buckingham at Student Planning and Assessment by internal phone number: 46430
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Room is currently booked for weeks: 10-19, 25-33, 39-47.