Current Quantum Systems Seminars

July 26th, 2022

Next Seminars:

If you have missed our previous seminars:

  • Date: Friday the 17th of May
Time: 3 pm AEST
Speaker: Harish Vallury
Bio: final-year PhD student at the University of Melbourne, Harish specialises in quantum computing and the development of algorithms for simulating condensed matter systems on near-term quantum computer hardware.
Title: Solving Spin Models on a Quantum Computer Using Hamiltonian Moments
Abstract: The determination of ground state properties of quantum systems is a key problem in physics and chemistry that presents a promising near-term use case for quantum computing. Such problems are typically approached via variational methods, which involve the preparation of a trial state on a quantum computer followed by direct measurement of its energy and other quantities of interest. However, current hardware constraints typically prevent an accurate description of the target ground state, limiting the performance of such approaches at any practically useful scale. To address this, we present a method that corrects the variational estimates of ground state observables via the quantum computation of Hamiltonian moments. The moments-based estimates not only deal with sub-optimal trial states, but are also highly robust to noise. We demonstrate the potential of this approach on real quantum hardware for models in quantum magnetism. Our method provides meaningful estimates of ground state properties in the intermediate circuit depth regime, pointing the way to quantum heuristic approaches to practically useful problems in the future.

  • Date: April 26th /2024- 14:00 Sydney Time
Speaker: Dr Lorcan Conlon, Quantum Scientist, A* STAR, Singapore.

Title: Approaching optimal entangling measurements on quantum computing platforms


Bio: Dr. Conlon, earned his PhD from the Australian National University (ANU), and has rapidly established himself in the field, with significant publications in Nature Physics and other prestigious journals. His research spans quantum optics, quantum information, and quantum metrology, pushing the boundaries of how we understand and utilize quantum systems.


Abstract: In this talk we will examine the role of entangling measurements for various tasks in quantuminformation. First, we present results showing the role of entangling measurements in quantum metrology. It is shown that entangling measurements on two copies of a quantumstate can lead to a quantum-enhanced measurement. However, due to noise in current real world quantum processors, entangling measurements on more than two copies of the quantum state perform worse than separable measurements. We discuss the implications of entangling measurements for uncertainty relations. Secondly, we examine the role of entangling measurements in quantum state discrimination. We present the first entangling measurement which achieves a smaller probability of error than the best possible separable measurement. Finally, we discuss the use of parameterised quantum circuits (PQCs) to extend these results. In particular, we investigate whether PQCs can help find efficient circuit decompositions and optimal measurements when large numbers of qubits are involved.

Nat. Phys. 19, 351–357 (2023).

  • Date: 23rd February 2024
Speaker: Deepesh Singh, School of Physics, The University of Queensland.

Title: Proof-of-work Consensus by Quantum Sampling


Bio: The first seminar of 2024 features Deepesh Singh, a final-year PhD student from The University of Queensland specializing in optical quantum computation and communication. Deepesh will enlighten us with his groundbreaking research on “Proof-of-work Consensus by Quantum Sampling.”


Abstract: Proof-of-work stands as a fundamental element in distributed consensus algorithms, crucial for randomly selecting a limited number of participants across extensive networks to authorize blockchain transactions. Present proof-of-work schemes, predominantly reliant on inverse hashing, exhibit significant energy consumption, driving the quest for more efficient methods while upholding security. In this seminar, we unveil the potential of the boson-sampling problem, a post-classical quantum algorithm feasible with contemporary technology, for quantum proof-of-work. Through the utilization of binning techniques, nodes faithfully executing the protocol converge towards binned statistical distributions, facilitating efficient classical verification through statistical consistency. Our scheme, initially presented in the context of Fock state boson-sampling, holds promise for compatibility with other forms of boson-sampling, including Gaussian boson-sampling. This protocol marks a significant milestone as perhaps the first real-world application for post-classical sampling problems within the current NISQ (noisy intermediate-scale quantum) era. Don’t miss the opportunity to explore the forefront of quantum computing and its practical implications. Join us as Deepesh Singh shares insights that could shape the future of distributed consensus algorithms.

  • Date: August 23/2023- 13.00 Sydney time

Recording: link

Speaker: Dr Kaitlin Smith, Quantum Software Manager Infleqtion USA.

Title – Scaling Quantum Computing Systems via Codesign 

Abstract – The full promise of quantum computation will only be realized if quantum devices scale. In addition to pursuing devices with more qubits, quantum researchers must 1) co-design software that pushes the frontier of existing machines and 2) build software models that guide future quantum system design toward optimal performance. Through the presentation of case studies, this talk will discuss the challenges and opportunities involved with scaling today’s quantum computers via hardware-software codesign. 

Bio – Kate is a quantum software manager at Infleqtion, Chicago. She directs projects related to optimized compilation, error mitigation, and simulation of quantum programs on a variety of qubit technologies. Prior to Infleqtion, Kate was an IBM and Chicago Quantum Exchange (CQE) postdoctoral scholar within the University of Chicago Department of Computer Science. In January 2024, she will join the Northwestern University Department of Computer Science as an assistant professor.

  • Date: 15 May 2023, 16.00 – 17.00 AEST

Speaker: Professor Andrew Doherty, University of Sydney,


Title: Building better qubit

Bio: Professor Andrew Doherty is a theoretical physicist in the School of Physics at The University of Sydney with more than 20 years of experience in quantum physics research. His research interests are in quantum control, quantum information, and quantum computing. He has extensive collaborations with experimentalists in a wide range of systems from quantum optics, including cavity QED and optomechanical systems, to condensed matter, including circuit QED and semiconductor quantum dots. Andrew completed his PhD at the University of Auckland in 2000 and did postdoctoral research at the California Institute of Technology before taking on academic positions at the University of Queensland and the University of Sydney. From 2019 to 2021 he worked for quantum computing company PsiQuantum, including as CTO from March 2020.

Abstract: Quantum computing is an incredibly exciting prospect, but current qubit technology has levels of noise that are many orders of magnitude greater than existing silicon-based conventional computing technologies. This can be addressed by implementing error correction to build reliable computers out of unreliable components. However addressing the error levels in current prototype qubit devices with existing error correction approaches implies that the first useful quantum computers will be large expensive devices. This motivate our research at the University of Sydney which aims to find both much better quantum error corrections schemes, as well as designing next generation qubits that have intrinsically low noise. In this talk I will describe the status of research on error correction and error protected qubits before describing some recent result from my research group.

  • Date: 29/3/23 17:00-18:00 Sydney time

Speaker: Dr Ben Criger, Senior Researcher at Quantinuum, UK.

Recording: link

Title: One-Bit Addition with the Smallest Interesting Colour Code

Abstract: There are fault-tolerant quantum computing techniques available to enhance the success probability of algorithms we wish to run, but the overheads associated with these techniques make most of them impossible to execute on available devices. In addition, fault-tolerant procedures that inflict large overheads also induce larger-than-necessary logical error rates. The dominant source of overhead in current fault-tolerant circuits is magic state distillation, which is necessary to perform non-Clifford gates in many fault-tolerant protocols using stabilizer codes. By contrast, there exist some quantum codes possessing transversal non-Clifford gates, facilitating fault-tolerant universal quantum computation without state distillation. In this work, we focus on an eight-qubit code, the “Smallest Interesting Colour Code”, demonstrating low-overhead procedures for Clifford operations and Pauli measurements, culminating in a fault-tolerant implementation of one-bit addition with 10 qubits and 26 CNots, suppressing the probability of classically detectable errors by more than an order of magnitude.

Biography: Ben Criger obtained his PhD from the Institute for Quantum Computing in 2014. He then worked as a post-doctoral researcher at the RWTH Aachen and TU Delft, before moving to the private sector in 2019. He now works for Quantinuum as the senior research scientist on the Cambridge quantum error correction team, whose mission is to make quantum computers work in real life.

  • Date: 28/2/23 15.00 – 16.00 AEDT

Recording: link

Speaker: A/Prof. Simon Devitt, Research Director at the Centre for Quantum Software & Information at UTS.

Title: Quantum graph states as a mechanism for error corrected compilation and resource estimation

Abstract: The utility of quantum computing has once again come to the forefront as researchers and companies begin to realise that error corrected quantum computers will be a requirement to realise any computational advantage using quantum hardware. The question is now being asked about how large this error correction overhead will be for a realistic quantum architecture, what are the size of the machines needed for useful quantum advantage and how to we both analyse and optimise the compilation of large algorithms such that resource counts drop as much as possible. I’m this talk I will outline a new compilation strategy that we are implementing in collaboration with the darpa quantum benchmarking program that will form the basis of an automated compilation and resource estimation toolset called bench-Q. This formalism, based on the measurement based computation framework and quantum graph states provides a useful mechanism for large-scale, error corrected compilation and allows for quantitative discussions related to hardware architectures needed to realise a scalable system.

Bio: A/Prof. Simon Devitt is Research Director at the Centre for Quantum Software & Information at UTS. His research focuses on Quantum Error Correction and Fault-tolerance, the design of large-scale quantum computing and communications systems and the compilation and resource optimisation of quantum algorithms.  Simon is the co-founder and managing director of h-bar quantum consultants and Co-founder of a new quantum startup, Eigensystems Pty Ltd. Having spent over a decade overseas working in the quantum computing programs of the UK and Japan, Simon has worked with numerous corporations, startups and VC firms on their expansion into the quantum technology space and advised multiple government agencies on multimillion-dollar R&D initiatives.

  • Date and time: November 30 2022

Title: Quantum computers – approaching fast

SpeakerProfessor Lloyd Hollenberg 


Abstract:  Quantum computers are now emerging from decades of development in research labs around the world. The hardware is advancing rapidly, with IBM’s state-of-the-art now at the 433 qubit level. The prospects of solving real-world problems on near-term quantum computers, will ultimately be determined by improvements in the level of hardware noise inducing errors in quantum logic, and the ability to mitigate their cumulative effects of in the computation results. This talk will review the current status of quantum computer systems, how one maps problems to the quantum context, the demonstrations of quantum advantage to date, and how the IBM Quantum Hub @ The University of Melbourne fits into this picture. No prior quantum knowledge necessary.

Biography Lloyd is a Melbourne Laureate Professor and Thomas Baker Chair in the School of Physics, University of Melbourne. He is also the Director of the IBM Quantum Hub at the University, established in 2018. He has published over 250 papers and is well known internationally for his work in quantum computing and quantum sensing.

  • Date and time: October 25 2022

Title: CSIRO Quantum Technologies Future Science Platform

Speaker: Professor Jim Rabeau 


Abstract:  In this talk, Jim will present the Quantum Technologies Future Science Platform and progress in seeding and growing quantum technology capability at CSIRO.  The purpose of the presentation is to give an update and stimulate future discussion ideas for opportunities to grow quantum technology research at Data61 and across all of CSIRO.

Biography: Jim has been leading the Quantum Technologies Future Science Platform at CSIRO since its inception in September 2021. Prior to this, he was a Professor at the School of Physics and Deputy Director at the University of Sydney Nano Institute. He has spent several years working in the industry, including as a program manager at Microsoft Quantum Computing. 


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