Colloquia

Colloquia

Our colloquia are held in E7B T5 on Tuesdays beginning at 1:00 pm. Our departmental colloquium series includes speakers from across all physics sub-disciplines, and is intended to be delivered at the senior undergraduate to graduate level, engaging an audience of researchers in areas as diverse as biophysics and astronomy. If arriving from off campus, we are accessible by train – just outside Macquarie Uni station – and paid parking is also available (from $10/hr). For up-to-date announcements about upcoming colloquia, please subscribe to the sci.physics mailing list, our RSS feed, and/or our iCalendar. Information regarding previous colloquia may be found in the left hand navigation bar.

Our Next Talk

01/11/16 – Overview of Free Space Optical Communications Research at the DST Group

Kerry Mudge

DST Group
Various factors affect the transmission of laser radiation through the Earth’s atmosphere, such as absorption and scattering from molecules and particulates. However, even for clear air, atmospheric turbulence leads to strong irradiance fluctuations on the transmitted laser light, an effect that is observed in the twinkling of stars. The propagation of lasers through the atmosphere has relevance to many military applications such as laser radar, ranging, remote sensing and directed energy. Our group is primarily focussed on free space laser communications (lasercom) applications for moving platforms. In this talk I’ll give an overview of the DSTG work programme in this area. Several techniques for characterising the optical channel as well mitigation strategies that we have investigated for combating the deleterious effects of optical turbulence on lasercom will be discussed. In addition, I’ll give an overview of the Defence Science and Technology Group (formerly DSTO).

Kerry Mudge

Semester 1 Talks

23/02/16 – Quantum Fluids of Light

Cristiano Ciuti

Univ. Paris Diderot, France
I will review recent theoretical and experimental advances in the manybody physics of light [1], including superfluid-like optical propagation effects. I will also give an overview of the recent frontier concerning strong photon-photon interactions and non-equilibrium strongly correlated phases of light, which can be achieved in arrays of coupled nonlinear resonators (e.g., semiconductor photonic microcavities, superconducting nonlinear quantum resonators).

[1] I. Carusotto, C. Ciuti, Rev. Mod. Phys. 85, 299 (2013).

Cristiano Ciuti

08/03/16 – The Quest for "Perfect" Diamond Qubits

Lachlan Rogers

University of Ulm
Colour centres in diamond are attractive architectures for qubits and spin-photon interfaces, but the currently available candidates are not perfect. The famous nitrogen vacancy (NV) centre fluorescence spectrum exhibits a number of undesirable characteristics including a strong phonon sideband and, typically, spectral diffusion of the zero-phonon line (ZPL). More recently the related silicon vacancy (SiV) centre has been shown to have exceptional optical properties, but a fundamentally limited spin coherence time of only 40 ns. What’s needed is a "smart search" for novel diamond qubits, hopefully pointing towards a future where colour centres can be "engineered" for specific applications.

The brand-new germanium vacancy centre will be presented as an example of this process. There is a tantalising possibility that germanium vacancies could combine the excellent spin coherence properties of NV with the superb spectral properties of SiV, leading to an almost perfect diamond qubit.

Lachlan Rogers

12/04/16 – Gigahertz Laser Frequency Combs

Ursula Keller

ETH Zurich
A modelocked laser can support not only very short pulses but at the same time very precise frequency metrology for the most accurate clocks. These ultrafast – or ultra-short pulse – lasers are dramatically impacting many areas of photonics, from basic science to industrial manufacturing and biomedicine. The design and performance of the lasers behind these applications is critical for new discoveries, creating new applications and opening new market opportunities. Modelocked lasers produce a frequency comb for which the frequency spacing (i.e. the pulse repetition rate) has been stabilized in the 1980’s achieving close to quantum-noise limited performance with diode-pumped solid-state lasers. However the stabilization of the frequency comb offset (i.e. the carrier envelope offset (CEO) frequency) remained a challenge and only has become possible 1999. Since then the field of optical frequency combs has evolved very quickly, and current applications range from high-precision spectroscopy over frequency metrology to ultra-high-speed optical communication. Many of these applications are based not only on one, but on two frequency combs such as dual-comb spectroscopy, asynchronous optical sampling, pump probe measurements and fiber Bragg grating sensing.

This talk will review our progress on gigahertz frequency combs based on modelocked semiconductor and solid-state lasers, stabilized by external silicon nitride waveguides or PCFs with an f-to-2f interferometer. Novel dual comb modelocked lasers are presented where an intracavity birefringent crystal in a MIXSEL is used for polarization-duplexing to obtain simultaneous emission of two modelocked beams from the same linear cavity sharing all components. Initially surprising was the observation that the cavity length adjustments to stabilize one polarization did not significantly affect the pulse repetition rate of the other.

Ursula Keller

19/04/16 – Recent Advances in the Physics and Applications of Metamaterials

Yuri Kivshar

Australian National University
Metamaterials, artificial electromagnetic media that are structured on the subwavelength scale, were initially suggested for the negative-index media, and later became a paradigm for engineering electromagnetic space and controlling propagation of waves. The research agenda has shifted towards achieving tunable, switchable, nonlinear and sensing functionalities of metamaterials, and also shaped around a new platform of two-dimensional metamaterials, or metasurfaces. A few years ago we put forward the concept of metadevices defined as photonic devices having unique and useful functionalities realized by structuring functional matter on the subwavelength scale.

More importantly, rapid progress in the fields of plasmonics and metamaterials is driven by their ability to enhance near-field effects with subwavelength localization of light, and a majority of such effects is usually associated with metallic nanoscale structures such as « meta-atoms » and « meta-molecules ». Recently, we observe the emergence of a new branch of nanophotonics aiming at the manipulation of strong optically-induced electric and magnetic Mie-type resonances in dielectric and semiconductor nanostructures with high refractive index. Unique advantages of dielectric resonant nanostructures over their metallic counterparts are low dissipative losses and the enhancement of both electric and magnetic fields that provide competitive alternatives for metal-based plasmonic structures including nanoantennas, nanoparticle sensors, and metasurfaces. Here, we review this new emerging field of nanophotonics and metamaterials and demonstrate that Mie-type resonances in dielectric nanoparticles and subwavelength-patterned dielectric structures can be exploited to boost performance of many nanophotonic metadevices. In addition, the coexistence of strong electric and magnetic resonances and resonant enhancement of magnetic field in dielectric nanoparticles bring new physics and entirely novel functionalities to simple geometries not much explored in plasmonic structures especially in the nonlinear regime.

This talk will summarize research on electromagnetic metamaterials and metadevices with different functionalities including the property of hyperbolic dispersion and all-dielectric nanophotonics.

Yuri Kivshar

26/04/16 – In the spirit of Joe Moyal: Phase-space physics – diabolism, whorls and tendrils, wignereal disease, superoscillations…

Michael Berry

University of Bristol
At the heart of conical refraction – Hamilton’s first physical prediction based on phase space – is a conical singularity: a diabolical point. Geometrical objects characterising the classical evolution of families of orbits are phase-space whorls (near stable fixed points) and tendrils (near unstable fixed points). The discordance between chaotic classical evolution and the corresponding quantum evolutions can be understood by the spreading of Wigner functions in phase space: slower as Planck’s constant increases. Notwithstanding the uncertainty principle, five equivalent local momenta can be associated with a quantum state, often describing spatial variations much faster than the Fourier content of the state might suggest.

Michael Berry

03/05/16 – Structure-Function Relationships in Complex Macromolecular Assemblies

Alastair Stewart

Victor Chang Cardiac Research Institute
The microscopic world of our cells is filled with complex molecular assemblies that dynamically move and interact to perform their function. This can range from molecular motors spinning thousands of times a minute, to large cages that massage molecules into their correct shape. Here we will discuss our recent work on two such proteins; ATP synthase, a multi subunit generator responsible for converting most of the chemical energy in the cell, and chaperonins, enormous complexes that use chemical energy to refold proteins.

Alastair Stewart

24/05/16 – Creating a Sense of Space – A Hitchhiker’s Guide to Spatial Hearing

David McAlpine

Macquarie University
Most sounds have an ‘out-thereness’ - they appear to originate from somewhere, and are usually attributed to the specific source, or sources, from which they originate. Nevertheless, unlike vision or touch, for example, the sensory end organs in the sense of hearing – the cochlea in the inner ear - contain no specialized receptors for determining the location of sound sources. To this end, cues to the location of a source must be computed from information that, of itself, is not spatial. Beyond this, our perception of the acoustic space in which we reside is also critical to our ‘connectedness’ to that space.

Starting with the work of Lord Rayleigh, this seminar will demonstrate how our understanding of spatial hearing has developed alongside the development of techniques used to assess brain function. With precision in the order of a few tens of microseconds, sensitivity to auditory spatial cues challenges our understanding of how technologies such as cochlear implants – devices that replace the function of the inner ear entirely - can be used to create a sense of space in individuals for whom the concept of sound is truly alien.

David McAlpine

31/05/16 – Keeping Astronomers (And Others) In The Dark

Fred Watson

Australian Astronomical Observatory
One of the more notable outcomes of last year's International Year of Light was an increased awareness of darkness. With light pollution damaging the night skies of all the world's cities, there is a growing call for better-designed outdoor lighting to improve the nocturnal environment and avoid wasted energy. This talk shows how today's technology makes that eminently attainable. It also looks closely at threats to the night sky of Siding Spring Observatory, where a pristine environment is of paramount importance. Reclaiming the night sky is not just for astronomers and nocturnal animal species, however - it is to the benefit of everyone.

Fred Watson

14/06/16 – Imaging with Nanodiamonds

Torsten Gaebel

University of Sydney
Nanodiamonds attract a lot of interest for quantum information technology, metrological sensors, and more recently as a probe of biological environments. Their easily adaptable carbon surface and non-toxic nature have allowed the use of dimaonds as vectors for therapeutic drug delivery, and as optical sensors of subcellular processes. However, a means of non-invasively imaging nanodiamonds in-vivo is still lacking. In this talk I will present various modalities to approach imaging of nanodiamonds in a biological environment.

Torsten Gaebel

21/06/16 – ASKAP, WALLABY and HI in Galaxies

Bärbel Koribalski

CSIRO
I will provide an update on the Australian SKA Pathfinder (ASKAP), highlight the planned surveys, including my ASKAP HI All Sky Survey (known as WALLABY), and outline our plans for Early Science with the first 12 ASKAP antennas. Our novel Phased-Array Feeds (PAFs) have a field-of-view of 30 square degrees, making ASKAP a fast 21-cm survey machine. WALLABY is expected to detect more than 500,000 galaxies and will tackle a large range of science projects. I will also highlight our data visualisation work of nearby galaxies and galaxy groups, with some focus on large and warped galaxy HI disks.

Bärbel Koribalski

28/06/16 – Structure and Dynamics at the Centre of the Milky Way

Andrew Walsh

Curtin University
The Central Molecular Zone (CMZ) of our Milky Way Galaxy contains 80% of all dense gas in the Galaxy, but holds only about 5% of current star formation. It is hotter, denser and more turbulent than anywhere else in the Galaxy - conditions analogous to distant galaxies used to estimate cosmic star formation rates. Yet we do not understand the star formation in the CMZ! I will present recent models of the CMZ to explain its unusual star formation properties. I will also introduce a way to make a 3 dimensional model of the CMZ with the hope that this can help us understand how star formation proceeds under extreme circumstances.

Andrew Walsh

Semester 2 Talks

09/08/16 – Intriguing Chemists and Upsetting Computer Scientists Using Light and Mirrors

Andrew White

University of Queensland
Quantum information is the lovechild of quantum physics and computer science. In this talk we look at the science of quantum information: what it is and isn't; why biologists, chemists, mathematicians and physicists might be interested in it; and where we are today. Along the way we review photonic quantum simulation and its prospects for scaling given the latest advances in quantum photonics, notably in sources, detectors, and nonlinear interactions.

Andrew White

16/08/16 – Probing the Origin of the Metal-to-Insulator Transition in Vanadium Oxides

Kevin Smith

University of Auckland
I will present the results of synchrotron radiation-excited photoemission, x-ray emission, and x-ray absorption spectroscopy studies of the metal-insulator transition (MIT) in strained VO2 thin films. Our results reveal that the MIT may be driven towards a purely electronic transition by the application of mechanical strain. Comparison with a moderately strained system demonstrates a crossover from Peierls-like to Mott-like transitions. Our observations have important implications for novel functional material engineering of VO2, suggesting a route towards circumventing the structural bottleneck in the ultrafast timescale of the MIT.

Kevin Smith

23/08/16 – CARMENES: Blue Planets Orbiting Red Stars

Andreas Quirrenbach

Heidelberg University
CARMENES is a new pair of spectrographs at the 3.5m telescope on Calar Alto in Southern Spain, which have been optimized to search for Earth-like planets orbiting red dwarf stars in the neighborhood of the Sun. We are using the Doppler method, which looks for the tiny wavelength shift of the stellar lines due to the motion of the star around the center of mass of the planetary system. Since the typical velocities are only of order 1 m/s, corresponding to a millipixel shift of the spectral lines on the detector, great care was taken in the design of the spectrographs to achieve high stability and precise calibration. Unlike previous similar instruments, CARMENES covers a wide wavelength range from 0.52 to 1.7 microns. This is not only beneficial for the sensitivity of the instrument for red dwarf stars, but also for distinguishing the signature of planets from "false positives", such as apparent radial-velocity variations induced by starspots. We are now in the first phase of a three-year survey targeting 300 red dwarfs with a sensitivity that is sufficient to find Earth analogs orbiting in the habitable zones of their host stars, i.e. at a distance from the star where liquid water can exist at the surface of the planet.

Andreas Quirrenbach

13/09/16 – Seeking the Best of Both Worlds -- Using Organic Materials to Make Better Nanowire Devices

Adam Micolich

UNSW
Nanowires are tiny needle-like semiconductor structures of order 100 nm in diameter and up to 10 microns long with considerable potential for use in device applications from advanced transistors to photonics and photovoltaics. An attractive feature of nanowires for transistor applications is the ability to more easily 'wrap' a metal gate around the nanowire to get strong electrostatic coupling, which brings reduced operating voltage. I will talk about our work on the development of wrap-around gates in nanowire transistors within the context of nanowire device research as a general direction. On our work, this will include some approaches where we abandon traditional materials like oxides and metals for interesting materials from organic electronics. These turn out to be remarkably useful for nanoscale devices, for example, by providing a new route to 'doping' nanowires from the outside using mobile ions in contrast to traditional internal atomic impurity doping which is difficult and problematic in tiny semiconductor structures. These new materials combinations may provide a new generation of hybrid ionic-electronic nanodevices for applications such as biosensing and neural signal transduction.

Adam Micolich

20/09/16 – Quantum Mechanics from a Non-Hermitian Perspective

Nimrod Moiseyev

Technion
The different cases for which a non-Hermitian Hamiltonian is required will be discussed. We focus on non-Hermitian quantum mechanics (NHQM) for calculating complex poles of the scattering matrix. These are associated with autoionization decay states of atoms, molecules, quantum-wells and quantum dots and with leaking modes in optical wave-guides. The exceptional point (EP) in the spectrum of the non-Hermitian Hamiltonian will be described. In particular the use of EP for the design and construction of atomic, molecular and optical time asymmetric switches will be described.

Our message is: there are physical phenomena that cannot be explained within the framework of standard (Hermitian) quantum mechanics. Moreover, in some cases it would be hard to design new devices which are based on these types of physical phenomena without the use of NHQM.

Nimrod Moiseyev

27/09/16 – The Natural Transformation in Mathematics

Ross Street

Macquarie University
The goal of the talk is to answer Prof Orsola De Marco's request to convey what it is that excites me in my chosen research field of Category Theory. This subject began in 1945 with papers focussing on examples and applications to group theory. However, the authors were prepared to look at the collection of all groups as a mathematical object; this was quite controversial at the time. A feature of the subject is the use of diagrams made of arrows. The arrows are an abstraction of functions f from one set A to another set B. More recently, a dual viewpoint, where f is depicted as a node with input string A and output string B, has led to deep connections with knot theory and invariants for low dimensional manifolds.

My talk will be about Mathematics but I hope the audience will see some connections with Physics. Please click here for a pdf version of the presentation of this talk.

Ross Street

04/10/16 – A Eureka Moment for Cell Colour Technology

Ewa Goldys

Macquarie University
Colour is a highly significant and ubiquitous biological signature. The medicine of yesteryear with its reliance on the human senses frequently used colour as a diagnostic tool. Remote sensing in agriculture and in marine science helps determine the condition of crops and the effect of climate change. In this work with my team, we explored the relevance of naturally occurring colour for biomedicine.

By making use of a century-old invention, the microscope, retooled with 21-st century light sources and powerful software, we have been able to exploit a commonly ignored trait inherent to all cells, their individual colour expression. The hyperspectral imaging technique pioneered by our team allows precise quantification of fluorescent colour of cells and tissues. Through the approach we are taking, and by using “big data” and high processing speeds of modern computers we are now able to unveil the biomolecular composition of cells and tissues. Biomolecules such as NADH, flavins, retinoids, cytochrome C and many others can now be non-invasively monitored.

With this advance, our research has created state-of-the-art sensing tools to monitor key biological processes such as metabolism as and when they happen, in real-time. These cellular and molecular measurements can be done in-vivo, in living organisms, expediting the potential for healthcare decisions based on the health needs of the individual, their genes and their unique biological characteristics.

This next-generation methodology offers a new window to noninvasively and rapidly detect major health conditions including neurodegeneration, cancer and diabetes. While probing the very limits of our understanding of life at the molecular level, this technology yields real world translational outcomes – outcomes that will support clinicians in making improved diagnosis and health decision for patients. The ensuing partnerships with industry will help create innovative technology platforms that add value to society.

Ewa Goldys

11/10/16 – Detecting Gravitational Waves from the Ground and Space

Daniel Shaddock

ANU
LIGO’s detection of gravitational waves from merging black holes was a landmark achievement in fundamental physics and a triumph of measurement technology. Scientists and engineers around the globe have been working to design an even larger interferometer to make measurements of lower frequency gravitational waves produced by much more massive sources. This Laser Interferometer Space Antenna, or LISA, will be a space mission that will shoot laser beams between three spacecraft separated by millions of kilometres in orbit around the sun. This talk will give an overview of the basics of gravitational wave interferometry and discuss the challenges of building a gravitational wave detector in space.

Daniel Shaddock

18/10/16 – NEID - NASA's new spectrograph to discover earth like exoplanets

Christian Schwab

Macquarie University
Extreme precision radial velocities is a key technique in the quest to discover earth-like planets. Our team was recently awarded a NASA contract to build a new visible range Doppler spectrograph for the WIYN telescope. This facility, called NEID, will provide better than 25 cm/s Doppler precision, leading the efforts of the US exoplanet community to obtain signatures of habitable worlds around solar type stars. In this talk, I will present the instrument architecture, our observing strategy to push into the habitable zone, and discuss the trade-offs in the optical and mechanical design that allow for this Doppler precision to become attainable.

Christian Schwab
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