Our focus areas

We conduct research in the foundations of quantum mechanics, quantum information and simulations, ultracold Fermi gases, Bose-Einstein condensates and atom lasers.

On this page:

Foundations of quantum mechanics

We are deeply engaged in the foundational aspects of quantum mechanics – striving to better understand the underlying principles that govern quantum systems. This broad spectrum of research areas enables us to drive innovation and solve complex problems in theoretical physics.

The well-known 1935 paper of Einstein et al. (EPR) led to the famous Bell theorem which rules out a whole class of local realistic theories – a result that has been called "the most profound discovery of science". The Schrödinger cat paradox raises an even more important issue – how to reconcile quantum realities with classical realities at the macroscopic level. 

Specific research topics include:

  • investigating the fundamental question raised by Einstein: does quantum mechanics provide a complete description of reality?
  • the measurement problem, nonlocality and causality in the Q-based objective-field model of reality for quantum mechanics
  • Bell inequalities and the EPR paradox, and other quantum paradoxes, in macroscopic systems.

Quantum information

Quantum information is a key area of our work, where we explore how to apply quantum mechanics in the development of new technologies – these pioneering advancements can revolutionise technology and data security. 

We are particularly interested in quantum memories as an enabling technology for many areas of quantum information. A quantum memory can store a quantum state indefinitely to be read out on demand. Possible quantum memory devices range from cold atoms to superconducting circuits and nano-oscillators.

Quantum computing and quantum supremacy

Quantum computers and other quantum technologies are under rapid development around the world. In this research, we investigate novel types of quantum technology. Our emphasis is on understanding the physics of the device.

At their heart, these are rather complex devices that obey the laws of quantum mechanics, which include such physical effects as stray coupling, dissipation and noise. We focus on network models like the coherent Ising machine, which solve useful optimisation problems like the traveling salesman and max-cut problems.

Large-scale quantum computers may have quantum advantage. This means that they can solve problems no digital quantum computer can solve. However, confirming such claims is essential. We treat Gaussian boson samplers, which are the largest of this type.

We have developed mathematical and computational tools that allow us to find, not just how accurately the quantum computer can solve, but also fast digital algorithms that we use as benchmarks for quantum advantage.

Specific research topics include:

  • physical models for novel quantum computers
  • validating quantum computation and quantum advantage.

Quantum simulations

The tunability of ultracold Fermi gases offers the exciting possibility to use them as a “quantum simulator” for studying other many-body quantum systems.

Most observable matter in our universe is composed of fermions (particles with half-integer spin). They are typically strongly interacting, and their understanding has been a long-standing grand challenge in modern physics. In the past decade, the high tunability of cold-atom systems at incredibly low temperatures (i.e. within a few nano-Kelvin above absolute zero) has realized various intriguing quantum phenomena.

An example is the Bardeen–Cooper–Schrieffer and Bose-Einstein condensation (BCS-BEC) crossover in potassium-40 and lithium-6 atomic gases, where the character of a Fermi superfluid continuously changes from the weak-coupling BCS-type to the BEC of tightly bound molecules upon increasing the interatomic interaction strength via Feshbach resonance.

Quantum phase-space simulations and stochastic methods

We are developing new algorithms based on phase-space representations for simulating quantum many-body systems. These include the world's best-tested and the largest known quantum simulations with experimental verification down to well below the vacuum noise level.

Our methods include: Wigner representations, positive-P representations, spin representations and general Gaussian phase-space methods. For simulations, we use the Swinburne Ngarrgu Tindebeek and gStar GPU-based supercomputers, as well as desktop GPU systems, programmed with Australian developed codes.

Our recent work includes quantum simulations of:

  • dynamic Bell violations
  • early universe quantum fluctuations
  • quantum opto-mechanics
  • large multipartite entangled spin systems
  • interferometers using Bose-Einstein condensates.

Strongly interacting photons

We investigate strongly correlated polaritons in quantum physics. Known as quantum fluids of light, polaritons are half-light, half-matter particles exhibiting frictionless, zero-energy-cost flows – an astonishing quantum behaviour known as superfluidity.

Our project expects to make a breakthrough in our understanding of polaritons in the strongly interacting regime far from equilibrium and fill in the knowledge gap towards the realisation of a superfluid of light at room temperature.

Quantum impurities and polarons

Why do polarons matter? Polarons lie at the heart of condensed‑matter physics, capturing the rich interplay between few‑body and many‑body phenomena.

In strongly interacting regimes where mean‑field and perturbative approaches break down, a lone impurity perturbs its environment only minimally, enabling exact – or nearly exact – solutions from a few‑body perspective.

Beyond fundamental interest, polaron and polaron–polaron interactions underpin the behaviour of numerous advanced materials, driving the need for a microscopic, quantitative understanding of their influence on material properties.

Projects include:

  • multidimensional polaronic spectroscopy
  • heavy polarons in a superfluid.

Ultracold Fermi gases

This area of research focus is motivated by the rapid experimental developments in degenerate Fermi gases. These systems are controlled at an unprecedented level and are well-described by quantum many-body models.

Our research involves themes designed to develop fundamental knowledge of the underlying physics and to provide theoretical guidance to experiments at Swinburne. 

Specific topics include:

  • few-body physics and virial expansions
  • low dimensional physics of multi-species Fermi gases
  • quantitative strong-coupling theory of ultracold Fermi gases
  • entanglement, correlations and coherent manipulations of ultracold Fermi gases.

Statistical mechanics

Statistical mechanics is the study of large physical systems like liquids, solids, gases and large molecules using statistical methods. Models such as hard spheres and self-avoiding walks require novel computational methods to study them. Related fields include physical combinatorics, climate change, polymer physics, and mathematical visualisation.

Bose-Einstein condensates and atom lasers

Atom lasers or Bose-Einstein condensates (BEC) exist at temperatures below one nano-Kelvin – a billion times colder than interstellar space. The bosonic atoms occupy an identical quantum state, so BECs are quantum systems on a macroscopic scale with atoms behaving as waves, but having particle-like qualities when detected.  

High-precision interferometry applications are being studied experimentally at Swinburne. Current theory projects on the quantum noise properties of BECs are:

  • quantum Brownian motion of impurities inside a BEC
  • dephasing, decoherence and entanglement effects in BEC interferometry.

Our research software

We have developed a number of codes for solving equations, constructing simulations and other functionalities across various research projects.

The extensible Stochastic Partial Differential Equation (xSPDE) code is a stochastic toolbox for construcing simulations and solving stochastic equations. Characterised by random noise terms, stochastic equations occur in science, engineering, economics and other disciplines.

With a modular design changeable to suit different applications, xSPDE includes strategies for calculating errors. At a basic level, just one or two lines of input are enough to specify the equation. For advanced users, the entire architecture is open and extensible in numerous ways.

xSPDE can solve ordinary and partial differential stochastic equations, including partial spatial derivatives such as the Maxwell or Schrödinger equations. Its general structure permits drop-in replacements of the functions provided.

Different simulations can be carried out sequentially to simulate the various stages in a process, such as an experiment. The code support parallelism at vector instruction level and thread level using Matlab matrix instructions and the parallel toolbox.

It also calculates averages of arbitrary functions of any number of complex or real fields and uses sub-ensemble averaging and extrapolation to obtain accurate error estimates.

Application packages included cover quantum stochastic differential equations, quantum phase-space simulations and stochastic projection methods.

xQSIM is a Matlab based package for simulating photonic networks. It is compatible with the full xSPDE simulator and has a shared multi-dimensional graphics package.

The focus of xQSIM is to simulate large boson-sampling quantum computers, which are currently the largest quantum architectures known.

The simulator can validate the output of such computers to an arbitrarily large scale, which permits quantitative comparison of theory with experiment and evaluation of quantum advantage claims.

Beclab is a Python package for numeric simulations of BEC in a harmonic trap. It calculates the dynamics of a condensate and supports ground state calculation via imaginary time propagation.

Users can collect various predefined observables (e.g. population, density, projections, energy and slices of density over given axes) and define custom ones.

Both classic GPE and Wigner representations are supported. For the latter, the package can automatically generate noise terms in the equations for given many-body losses.

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Contact the Centre for Quantum Science and Technology Theory

There are many ways to engage with us. For more information about our centre, please email our centre director Professor Margaret Reid at mdreid@swinburne.edu.au.

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