Title: New  results in reverse time diffusion modelling

Abstract: Continuous-time diffusion models normally are considered to evolve forwards in time. Reverse time models can be defined however, and have played a critical role in the construction of AI-style algorithms for generating images from text.  A significant logical gap exists in applying the continuous-time theory to the AI application because the latter is essentially dealing with discrete-time equations, and the rigorous connection of discrete-time and continuous-time stochastic equations over an infinite time interval is hazardous. This talk will cover results on the direct construction of a discrete-time reverse model from a discrete-time forward-time reverse model that bypasses the difficulty associated with relying on continuous-time theory. 

Title: Negative Imaginary Power Grids: Robust Virtual Transmission Line Technology

Abstract: Australia must continue to transition its electric power grid to renewable energy, such as wind and solar, backed by battery storage. However, integrating renewable energy technologies into the power grid and supporting the substantial increase in electricity required to electrify everything (e.g., electric cars) is a significant challenge, particularly while ensuring the power system remains affordable, reliable, and safe. In this talk, I will introduce a new control framework based on negative imaginary systems theory that enables the electric grid to operate more efficiently, reducing the need for a massive expansion of electricity grid infrastructure. This control framework will use battery storage for robust control action and advanced sensors for precision measurement to avoid the massive cost associated with building more transmission corridors and other grid expansions. The aim is to meet the challenge of transforming power systems for a net-zero emissions future in a cost-effective way while maintaining the stable and reliable power grid that we have known for over a century.

Title: Nonclassical robustness questions in quantum control design

Abstract: Robustness in some quantum control designs—typically the linear noncommutative quantum optics as developed by Petersen and his co-workers culminating in the Hinf-controlled quantum stochastic equation—fits within the classical paradigms developed in the 1980’s. Other quantum problems, however, require a complete rethinking of the very concepts of robustness and sensitivity. Closely related to robustness are some questions related to whether the classical limitations of robustness versus fidelity hold in the quantum world. Quantum designs where such questions arise include spintronics, ultra-cold atoms in optical lattices, and quantum gates. In this talk, we will focus on quantum systems where classical paradigms are challenged by the bilinear nature of quantum dynamics and its nonlinearities. Ultra-cold atom interferometry for quantum inertial navigation will serve as illustrative application. 

Title: From quantum control and physical realizability to optimal field states for quantum gates

Abstract: I will give some reflections on my time as a PhD student under Ian Petersen's supervision and an overview of our key results concerning quantum control and the physical realizability of quantum systems. I will also present some recent results from an ongoing collaboration with Julio Gea-Banacloche regarding protocols for generating optimal field states for performing quantum gate operations, and how after a gate operation is performed, the resulting field can then be “recycled” by subsequent interaction with a set of ancilla qubits, restoring it to its optimal state. I will conclude by considering the case of simultaneously driven atoms.

Title: Efficient quantum algorithm for simulating Markovian open quantum systems

Abstract: Simulating closed or open quantum systems is an essential task for understanding complex physical phenomena and advancing quantum technologies including controlled quantum systems. However, this task is very hard for classical computers, which in general needs exponential computational resources both in space and time. Quantum computers offer promising approach to this problem, and extensive studies have been done particularly for closed systems. Yet it is still just beginning for open quantum systems. In this talk, I will present our recently-developed quantum algorithm for simulating general Lindblad dynamics, that achieves both logarithmically short number of operations and number of ancilla qubits. 

Title: Negative imaginary systems theory: A brief introduction

Abstract: The negative imaginary systems notion broadly means that the output of a system follows, but lags behind, a sinusoidal input by not more than 180 degrees phase lag. In a SISO LTI setting, this means that the positive frequency branch of the Nyquist plot has a negative imaginary part from where the name arises. It turns out that these systems are highly suited to capture, for example, inertial dynamics of mechanical systems (e.g. robots, large space structures, etc) because the input-output map from force (or torque) actuation to colocated position (or angular position) measurement possess this property as a simple consequence of Newton’s second law of motion. Negative imaginary systems theory is related, but complementary, to passivity theory. This talk will give a brief introduction to negative imaginary systems theory and will outline some of the key results in this area.

Title: TBC

Abstract: TBC

Title: On the Control of Open Quantum Systems

Abstract: We provide an overview of control strategies for open quantum systems, that is, quantum systems interacting with an environment. Such interactions lead to a loss of information to the environment, a phenomenon commonly referred to as decoherence. One of the principal challenges in controlling open quantum systems is therefore the compensation of decoherence effects. To address robustness issues, feedback control methods are considered. We then study the feedback stabilization of open quantum systems under repeated indirect measurements, where the evolution is described by quantum trajectories. In particular, we present our recent results concerning the asymptotic behavior, convergence speed, and stabilization properties of these trajectories. Finally, we discuss the robustness of feedback strategies with respect to realistic imperfections.

Title: Control System Innovations for Atomic-Precision STM Imaging and Lithography

Abstract: The scanning tunneling microscope (STM), a Nobel Prize-winning instrument, has long been central to surface science, enabling atomic-scale imaging, spectroscopy, and — more recently — atomically precise lithography for the development of next-generation quantum electronic devices. Yet despite these remarkable advances in application, the fundamental feedback control loop governing STM operation has remained largely unchanged for nearly four decades. This talk presents recent work from my laboratory aimed at fundamentally reimagining the STM control architecture. I will describe new control strategies and their demonstrated impact on STM performance during both imaging and lithography operations, and discuss the broader implications for atomically precise advanced manufacturing.