Theme 1A: Photonic Sensors & Imaging

Lasers are the power tools in the world of science. In this theme we use their extraordinary light to see, hear, smell and feel far beyond the reach of our senses. When you fire a laser at an object there is a tremendous amount of information in the light that bounces back. We use different colours, pulses and powers of laser light to learn about the structure and function of biological tissue and many other surfaces.



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Our expertise in interpreting the way light interacts with matter has led to many unexpected and fruitful collaborations across New Zealand and overseas. We are developing sensors to sort sperm for the dairy industry, detect bacteria on carcasses, grade the quality of meat and locate blossoms on kiwifruit plants. We are working with engineers and medical researchers to develop a technique for detecting eye disease, a new method for measuring the intensity of skin burns and a force sensor for keyhole surgery. We are also working with geophysicists to measure vibrations deep beneath New Zealand’s alpine fault.

Our sensing and imaging projects are underpinned by a strong focus on theory and numerical modelling. Our researchers are world renowned for their understanding of nonlinear optics, when light stops behaving according to the normal rules. We are able to exploit these nonlinear effects to create novel sensing and imaging technologies.

Theme 1B: Photonic Sources & Components

They say workers are only as good as their tools. This theme is developing new and improved lasers, fibre optic cables and other optical tools to open up new frontiers for research and applications. We work in close collaboration with the other three themes to provide tools to enhance their research and probe further into the quantum world.



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We are world-renowned for our expertise in fibre lasers, which are versatile, lightweight and cheap to produce. We develop them for use as cutters, sorters and sensors for a wide variety of industrial and science applications. We are also well known for our strength in nonlinear optics; understanding what happens when light stops behaving by the normal rules. Our fundamental theories and numerical models are used by top research groups across the world and have led to advances in the development of optical frequency combs, cavity solitons and other nonlinear devices that could revolutionise the internet and many other fields.

Theme 2A: Quantum Fluids & Gases

The quantum realm is the wild west of modern science. Although we know some of the basic rules, the vast majority of quantum interactions remain uncharted. In this theme we explore cold atom physics, which is like a playground for quantum phenomena.



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By cooling atoms to just above absolute zero and precisely controlling their state, we have the ability to create and observe almost any quantum effect we can think of. We run experiments and develop theory to investigate quantum phenomena such as quantum vortices, quantum turbulence, the conditions before the Big Bang and biological processes involved in photosynthesis. We are exploiting this new understanding to develop quantum technologies such as extremely precise gravitometers and clocks. We are world renowned for our legacy in quantum theory and despite our modest budget have developed outstanding experimental facilities which are enabling world-class results.

Theme 2B: Quantum Manipulation & Information

It is one thing to understand how the quantum world works; it requires another level of precision and control to build reliable devices and systems that exploit quantum phenomena.



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This kind of ‘quantum engineering’ is the focus of this theme. Through precise observation and control of the interactions between photons of light and atoms we are contributing to the development of a new generation of quantum technologies. Our aim is to exploit the weird aspects of the quantum world like quantum superposition (the ability of a quantum particle to exist in more than one state at once) and quantum entanglement (when several particles behave as if they were a single entity).

Our researchers have record ability to isolate and control the motion of single atoms. We can move atoms around with laser light and stick them together to create completely new molecules and conduct ultra-precise experiments. Our research is contributing to the development of quantum computers capable of solving extremely complex problems. We are looking at novel ways of creating qubits, the fundamental processing units for quantum computers, and developing solutions for quantum memory and quantum debugging. Quantum communication is the focus of several projects. We are working on a technique to enable communication between quantum computers over large distances. This involves translating single microwave photons, which quantum computers operate on, to optical photons, which are easily transported down optical fibres. We are also contributing to the fundamental theory behind quantum communication networks and quantum measurement.

Date:

Friday 13th March 2020

Title:

Spectroscopic assessment of NZ plums

Presenter:

Sara Miller

Abstract:

Non-destructive assessment of fruit for parameters such as ripeness, postharvest damage and bioactive compounds are desirable. Raman, near-infrared (NIR) and mid-infrared (MIR) spectroscopic techniques yield compositional information in a non-destructive manner making these techniques a great candidate for in-line assessment of fruit. These vibrational spectroscopic methods were evaluated for the potential to quantify bioactive compounds of interest to NZ industry and the consumer in commercially grown New Zealand plums. These spectroscopic datasets were assessed using qualitative, quantitative and classification based multivariate analysis methods. Principle component analysis qualitatively demonstrated groupings based on the cultivar and growing location (Figure 1). Four cultivars grown in two different growing locations were assessed for total anthocyanin content, vitamin C content, phenolic content and total antioxidant capacity. These parameters (measured using traditional methods) were correlated to the spectroscopic data using partial least squares regression and support vector machine classification (where appropriate). Raman and MIR showed the most promise for quantifying vitamin C content and Raman showed the most promise for quantifying anthocyanin content.
Figure 1. Scores plot highlighting variance based on growing location for one cultivar of NZ plums.

Date:

Friday 21st February 2020

Title:

“Quantum control with high-frequency drivings“

Presenter:

Assoc Prof Sandro Wimberger

Abstract:

Quantum adiabatic driving is one of the pillars of time-dependent quantum control. However, the limitations imposed by the coherence times are typically in sharp contrast with the necessity of slow evolutions imposed by the adiabatic theorem. A method will be presented for accelerating adiabatic state transfer for few-level systems. This works by introducing suitably tailored fast oscillations in the intrinsic parameters of the original Hamiltonian: the oscillations mediate an effective Hamiltonian dynamically compensating for undesired transitions. It will be shown how the protocol can be exploited for accelerating STIRAP state transfer and for producing entanglement between two qubits, e.g., in a circuit QED setting.

Date:

Friday 14th February 2020

Title:

High-Resolution Spectroscopic Studies of Upconverting Lanthanide-Doped Fluoride Nanoparticles

Presenter:

Professor Michael F. Reid

Abstract:

Lanthanide-doped luminescent nanoparticles are important candidates for low-toxicity imaging agents and nano-thermometers for biomedical applications [1]. Lanthanide ions doped into bulk CaF2 and SrF2 crystals are known to form a variety of sites, and to form clusters at concentrations as low as 0.01 mol%, becoming the dominant centres by 0.1 mol% [2, 3]. This clustering gives enhanced energy transfer, promising significant improvements in applications requiring up-conversion or down-conversion via energy transfer. Most work on lanthanide-doped CaF2 and SrF2 nanoparticles has made use of low-resolution spectroscopy at high temperatures [4,5], and was therefore unable to clearly discriminate between the different sites. In this work we present high resolution laser spectroscopy of flouride nano-particles doped with Eu3+, Yb3+, and Er3+ at cryogenic temperatures (10 K), including site-selective excitation, emission, lifetime, and upconversion measurements. These techniques allow us to relate the site distribution to those observed in bulk crystals and to better understand the optimal excitation for upconversion [6]. We will also discuss the use of magnetic fields to modulate the energy levels.

Date:

Friday 15th November 2019

Title:

Anderson localisation in two dimensions: insights from Localisation Landscape Theory, exact diagonalisation, and time-dependent simulations

Presenter:

Dr. Sophie Shamailov

Abstract:

Motivated by rapid experimental progress in ultra-cold atomic systems, we aim to provide a simple, intuitive description of Anderson localisation that allows for a direct quantitative comparison to experimental data, as well as yielding novel insights. To this end, we advance, employ and validate a recently-discovered theory – Localisation Landscape Theory (LLT) – which has unparalleled strengths and advantages, both computational and conceptual, over alternative methods. We focus on two-dimensional systems with point-like random scatterers, although an analogous study in other dimensions and with other types of disorder would proceed similarly. We use LLT to compute the localisation length and the mobility edge, testing our findings against more traditional techniques. Furthermore, we propose an experiment that optimally detects Anderson localisation and link the simulated observations of such an experiment to the predictions of LLT. Finally, we utilise LLT to uncover a connection between the Anderson model for discrete disordered lattices and continuous two-dimensional disordered systems, which provides powerful new insights.

Date:

Friday 24th October 2019

Title:

Experiments with optical nano fibres and cold atoms

Presenter:

Dr. Maarten Hoogerland

Abstract:

The experiment using cold atoms and optical nano fibres has come back online. I will discuss the current plans and future vision of this experiment.

Date:

Friday 18th October 2019

Title:

Yrast States of the attractive Hubbard model in the 1D-2D crossover

Presenter:

Dr. Ulrich Ebling

Abstract:

We use the “Full Configuration Interaction Quantum Monte-Carlo”-method (FCIQMC) to study properties of the Fermi Hubbard model with attractive on-site interaction at low densities. Among the advantages of FCIQMC compared to other QMC methods is that it conserves total center-of-mass momentum. We therefore can access not just the ground state with zero total momentum, but the lowest-lying excitations with non-zero momentum, called yrast states. It has been shown that in a homogenous 1D superfluid, dark solitons appear as linear combinations of yrast states around the maxima of the yrast spectrum. We examine this behavior in the crossover to the 2D system, by adding more and more lattice rows' in the transverse direction, a regime where analytic solutions are not known and FCIQMC can give us the exact wave function of yrast states. There, we can obtain parameters such as the effective mass of dark solitons and look for signatures of the expected decay of a soliton into a pair of vortices.

Date:

Friday 27th September

Title:

Ultrastrong coupling between antiferromagnetic magnon modes and a microwave cavity. The road to upconversion in fully concentrated rare-earth ion crystals.

Presenter:

Jono Everts

Abstract:

Most investigations of rare earth ions in solids for quantum information have used rare earth ion doped crystals. Here we analyse the conversion of quantum information from microwave photons to optical frequencies using crystals where the rare earth ions, rather than being dopants, are part of the host crystal. The potential of large ion densities and small linewidths makes such systems very attractive in this application. Collective spin resonances known as magnons mediate the conversion process. Magnon modes are theoretically well studied in materials with isotropic g-tensors, and experimentally well studied in YIG, however little research has been carried out in rare-earth crystals. It is therefore important to obtain a better understanding of the magnon modes within the rare-earth crystals that are suitable for our conversion device. We present preliminary results for investigations carried out in the crystal Gadolinium Vanadate.

Date:

Friday 23rd August2019

Title:

Photoassociation dynamics of two Rb-85 atoms

Presenter:

Dr. Marvin Weyland

Abstract:

The formation of molecules is an important process in physics and chemistry. One way to initiate molecule formation is photoassociation of two atoms, where a laser pulse is used to transition from two free atoms to a molecule. This has been observed in many-body ensembles for several decades, but new techniques make it possible to investigate photoassociation using exactly two atoms, thereby allowing a much higher degree of control over the process and the created molecule. Our goal is to determine the fundamental limit for the time it takes to form a molecule in the two-body regime. We prepare a single Rb-85 atom in an optical dipole trap and prepare its internal quantum state. Creating two such traps with one atom each and merging them adiabatically allows the preparation of a trap which holds exactly two atoms in known states which we can photoassociate to a molecule. Working with exactly 2 atoms we can also investigate the photoassociation dynamics in the two-body regime. We find that a single photoassociation rate is not sufficient to describe the observed dynamics of two atoms. Instead, two different timescales for photoassociation are necessary to describe our observations. The dynamics likely originate from the 2-atom system being non-chaotic. The interactions thereby depend on the relative motion states which were initially populated. These additional dynamics disappear when a third atom is added to the system We observe the dynamics of molecule formation as a function of intensity of the photoassociation light as well as the temperature of the atoms in the trap. Even with the additional dynamics, our measured photoassociation timescales agree with a unitarity limited inelastic scattering rate at high photoassociation power. We are able to observe saturation of the rate coefficient which is in good agreement with the theoretical limit.

Date:

Friday 16th August 2019

Title:

Giant vortex clusters in a quantum fluid

Presenter:

UoO Senior Lecturer, Ashton Bradley

Abstract:

Atomic Bose-Einstein condensates (BECs) provide a uniquely controllable setting in which to study quantum fluid dynamics. In a stirred superfluid, quantized vortices typically proliferate, injecting linear and angular momentum into the fluid. In 1949, while studying the point-vortex model, Onsager predicted that confinement of quantum vortices can produce a surprising result: the possibility of vortices reaching negative temperatures. Negative temperature states contain significant energy, forming a collective storm of vortices circulating in the same direction: a giant vortex cluster. Vortex cluster states are the quantum analogue of the Great Red Spot, visible on the surface of Jupiter as a manifestation of classical fluid turbulence. I will describe our work on the theory of giant vortex clusters, and joint work with the BEC group at the University of Queensland to observe them for the first time in a quantum gas controlled by a digital micromirror device. Despite expectations that such high energy states should be unstable, we observe giant quantum vortex clusters with very long lifetimes. Our work confirms Onsager’s prediction after some 70 years, and opens the door to a new regime for quantum vortex matter at negative absolute temperatures, with implications for quantum turbulence, helium films, nonlinear optical materials, and fermi superfluids.

Date:

Friday 9th August 2019

Title:

Using vibrational spectroscopy as a photonic tool to extract actionable insight from complex materials

Presenter:

Dr. Michel Nieuwoudt

Abstract:

Much information lies hidden in complex materials about their molecular composition, structure and interactions. Because Raman and Infrared spectroscopy measure molecular vibrations, they can extract this information from complex materials like food, biological tissue and bone. In addition, they can do this both non-invasively and rapidly and so provide faster alternatives to chemical reference testing or biochemical assays. Ongoing advances in photonics and optical instrumentation enable the development of increasingly sophisticated light sources and smaller, portable spectrometers with more options to analyse complex materials in situ and, in the case of living tissue, in vivo, so that Raman and infrared spectroscopies are fast emerging as tools in medical diagnostics and food safety. There is also significant interest in imaging technologies that combine spatial and/or morphological information with the chemical information inherent in vibrational spectra. Diverse fields such as food and forensic science, medical imaging technologies, the cosmetic and pharmaceutical industries are increasingly adopting chemical imaging as invaluable tools in their research. These include hyperspectral imaging using near infrared (NIR), mid infrared (MIR), Raman and fluorescence spectroscopy. Spectroscopic techniques generate large spectral datasets and require multivariate statistical tools to analyse the large amounts of data. Chemometrics can be used to extract relevant information from this data to find patterns or trends, optimize experiment design, monitor reactions, determine composition, detection limits, or predict future behaviour. In this seminar I will describe how vibrational spectroscopy with chemometrics can be used rapidly and non-invasively to gain meaningful insight from materials as diverse as milk, skin, cortical bone and iron passive film.