Doctor Terry Frankcombe

Quantum dynamics calculations in molecular scattering are demanding. Indeed, after 40 years of development the state of the art is simulating reactions in five atom systems.  Gaussian wave packets (GWPs) offer a promising alternative to the essentially grid-based methods that dominate the field, allowing methods with better scaling and much more sensible demands on potential energy surface evaluation.  In this talk I shall give an overview of the GWP methods being developed at ANU, including a sneak peek at our new “Basis Expansion Leap” method.

Professor Carlton Caves, University of New Mexico.
The approach of Josephson-effect linear amplifiers to the fundamental
quantum limit on noise temperature has sparked renewed interest in
low-noise linear amplifiers.  The standard, by now highly developed,
discussion of quantum limits on phase-preserving linear amplifiers
characterizes amplifier noise performance in terms of second moments
of the added noise, i.e., in terms of noise temperature or noise
power.  We have generalized this standard discussion to provide a
complete characterization of the quantum-mechanical restrictions on
the entire probability distribution of added noise.  Meanwhile, there
have been proposals for and experiments related to a different class
of linear amplifiers, which actually subtract noise from the output,
but which operate only part of time.  I discuss here what is known
about quantum limits on the operation of such probabilistic
amplifiers.

This work was carried out with Shashank Pandey, Zhang Jiang, and
Josh Combes, all of UNM, and parts were also done with Marco Piani
of the Perimeter Institute.

The periodic potential imposed by the crystal lattice allows new effective Hamiltonians for electrons to be generated which may be qualitatively different than the Schrodinger equation for a free electron at low energies. I will discuss two striking recent examples. In graphene, the basis of two identical atoms in the honeycomb lattice leads to a massless Dirac Hamiltonian with an emergent spin-1/2 “pseudospin” spinor coupled to momentum. In the three-dimensional topological insulators, strong spin-orbit coupling leads to a Hamiltonian which is topologically distinct from the free-electron case, which gives rise to emergent metallic states at the boundaries (surfaces) of the material. These surface states also have a Dirac effective Hamiltonian, but with momentum coupled to the intrinsic electron spin. I will discuss how these materials are made, and how they are used to enable the study of Dirac electrons in the laboratory.

What has been the most profound discovery, progress or idea that has emerged in astronomy over the last decade? And what will be the most important challenge in astronomical research in the next decade? These questions are at the heart of our discipline, but we rarely venture outside of our own niche areas. I will attempt to focus on the broad picture underlying the field of star formation and discuss the requisite conditions for sustained progress in this field, aided by recent achievements in the context of my group’s star cluster research.

Serge Haroche and David Wineland shared the 2012 Nobel Prize in Physics for pioneering the coherent control of single quantum systems. Haroche’s work used photons in a single superconducting microwave cavity; Wineland’s  used one or more single trapped ions. Their work laid the foundations for a nascent quantum technology and provided experimental answers to foundational questions such as quantum measurement and decoherence. In this talk I will describe the science behind their key experiments and look forward to a future quantum technology based on coherent quantum control.

The detection of explosives, particularly with compact portable sensors, remains an ongoing security and technological challenge. The quenching of the fluorescence of organic semiconductors by explosives such as TNT is one promising solution. In this talk I will provide an overview of the principles behind fluorescence quenching before introducing a series of compounds for sensing that vary in terms of size, shape and the number of chromophores. As such, these compounds provide an ideal platform for understanding the processes that govern the quenching of the fluorescence in both solution and thin films. By performing simultaneous measurements of the neutron reflectivity and fluorescence intensity of thin films we can monitor the diffusion and concentration of vapours of a TNT-analogue within the film and obtain quantitative measurements of the quenching efficiency. These experiments provide insights into not just the sensing process but also the photophysical and electronic properties of the sensing materials.

Speaker: Professor Kristian Helmerson (Monash University)
Date: 7th September 2012

Modern electronic devices rely on the transport and interaction of electrical charge, mainly in semiconductors. While we have become extremely proficient at moving electrical charge through materials for various applications, this is only the beginning. Atoms possess a number of properties not found in electrons, such as a rich internal structure, tunable interactions and extremely long coherence times. “Atomtronics” seeks to exploit these and other properties to enable new types of devices with new capabilities that are not possible by simply manipulating charge in current electronics.

The degree of control over atoms now available with ultracold atomic gases enables the construction of atomtronic devices with designer capabilities. In my talk, I will describe atomtronics and the potential capabilities of such devices. I will provide some examples from the ultracold atoms community including my own research on realizing an atomic-gas analog of a SQUID or superconducting quantum interference device.