meet the meQuanics - Quantum Computing Discussions

During this time of lockdown, the centre for quantum software and information (QSI) at the University of Technology Sydney has launched an online seminar series. With talks once or twice a week from leading researchers in the field, meQuanics is supporting this series by mirroring the audio from each talk. I would encourage if you listen to this episode, to visit and subscribe to the UTS:QSI YouTube page to see each of these talks with the associated slides to help it make more sense. https://youtu.be/4KIXVQtR9Qw Free-Fermion Solutions and Frustration Graphs TITLE: Characterization of free-fermion-solvable spin models via graph invariants SPEAKER: Dr Adrian Chapman AFFILIATION: ARC Centre of Excellence for Engineered Quantum Systems (EQUS), University of Sydney, Australia HOSTED BY: A/Prof Chris Ferrie, UTS Centre for Quantum Software and Information ABSTRACT: Finding exact solutions to spin models is a fundamental problem of many-body physics. A workhorse technique for exact solution methods is mapping to an effective description by noninteracting fermions. The paradigmatic example of this is the Jordan-Wigner transformation for finding an exact solution to the one-dimensional XY model. Another important example is the exact free-fermion solution to the two-dimensional Kitaev honeycomb model. I will describe a framework for recognizing general models which can be solved this way by utilizing the tools of graph theory. Our construction relies on a connection to the graph-theoretic problem of recognizing line graphs, which has been solved optimally. A corollary of this result is a complete set of constant-sized frustration structures which obstruct a free-fermion solution. We classify the kinds of Pauli symmetries which can be present in models for which a free-fermion solution exists, and we find that they correspond to either: (i) gauge qubits, (ii) cycles on the free-fermion hopping graph, or (iii) the fermion parity. Clifford symmetries, except in finitely-many cases, must be symmetries of the free-fermion Hamiltonian itself. We expect our characterization to motivate a renewed exploration of free-fermion-solvable models, and I will close with an elaborate discussion of how we expect to generalize our framework beyond generator-to-generator mappings. RELATED ARTICLES: Characterization of solvable spin models via graph invariants. Quantum 4, 278 (2020). Characterization of solvable spin models via graph invariants: quantum-journal.org/papers/q-2020-06-04-278/ OTHER LINKS: Adrian Chapman Webpage: https://equs.org/users/adrian-chapman

During this time of lockdown, the centre for quantum software and information (QSI) at the University of Technology Sydney has launched an online seminar series. With talks once or twice a week from leading researchers in the field, meQuanics is supporting this series by mirroring the audio from each talk. I would encourage if you listen to this episode, to visit and subscribe to the UTS:QSI YouTube page to see each of these talks with the associated slides to help it make more sense. https://youtu.be/2syrO_asU5Y Hardness of Random Circuit Sampling (Google's supremacy experiment) TITLE: Cayley Path and Quantum Supremacy SPEAKER: Dr Ramis Movassagh AFFILIATION: MIT-IBM Watson AI Lab, Cambridge MA, USA HOSTED BY: Prof Michael Bremner, UTS Centre for Quantum Software and Information ABSTRACT: Given the large push by academia and industry (e.g., IBM and Google), quantum computers with hundred(s) of qubits are at the brink of existence with the promise of outperforming any classical computer. Demonstration of computational advantages of noisy near-term quantum computers over classical computers is an imperative near-term goal. The foremost candidate task for showing this is Random Circuit Sampling (RCS), which is the task of sampling from the output distribution of a random circuit. This is exactly the task that recently Google experimentally performed on 53-qubits. Stockmeyer's theorem implies that efficient sampling allows for estimation of probability amplitudes. Therefore, hardness of probability estimation implies hardness of sampling. We prove that estimating probabilities to within small errors is #P-hard on average (i.e. for random circuits), and put the results in the context of previous works. Some ingredients that are developed to make this proof possible are construction of the Cayley path as a rational function valued unitary path that interpolate between two arbitrary unitaries, an extension of Berlekamp-Welch algorithm that efficiently and exactly interpolates rational functions, and construction of probability distributions over unitaries that are arbitrarily close to the Haar measure. RELATED ARTICLES: Unitary-valued paths, and an algebraic proof technique in complexity theory: https://ramismovassagh.wordpress.com/... Cayley path and quantum computational supremacy: A proof of average-case #P−hardness of Random Circuit Sampling with quantified robustness: https://arxiv.org/abs/1909.06210 Efficient unitary paths and quantum computational supremacy: A proof of average-case hardness of Random Circuit Sampling: https://arxiv.org/abs/1810.04681 OTHER LINKS: Ramis Movassagh Personal Webpage: https://ramismovassagh.wordpress.com/ MIT-IBM Watson AI Lab: https://mitibmwatsonailab.mit.edu/

During this time of lockdown, the centre for quantum software and information (QSI) at the University of Technology Sydney has launched an online seminar series. With talks once or twice a week from leading researchers in the field, meQuanics is supporting this series by mirroring the audio from each talk. I would encourage if you listen to this episode, to visit and subscribe to the UTS:QSI YouTube page to see each of these talks with the associated slides to help it make more sense. https://youtu.be/Dg6Q_F9uI8s Silicon spin qubits gain traction for large-scale quantum computation and simulation. TITLE: A Scalable “Spins-Inside” Quantum Processor and Simulator SPEAKER: Prof Lieven Vandersypen AFFILIATION: QuTech, Kavli Institute of Nanoscience, Dept of Quantum Nanoscience, Delft University of Technology, Netherlands HOSTED BY: Dr JP (Juan Pablo) Dehollain, UTS Centre for Quantum Software and Information ABSTRACT: Excellent control of over physical 50 qubits has been achieved, but can we also realize 50 fault-tolerant qubits? Here quantum bits encoded in the spin state of individual electrons in silicon quantum dot arrays have emerged as a highly promising avenue. In this talk, I will present our vision of a large-scale spin-based quantum processor, and our ongoing work to realize this vision. I will also show how the same platform offers a powerful platform for analog quantum simulation of Fermi-Hubbard physics and quantum magnetism. RELATED ARTICLES: Physics Today 72(8), 38 (2019) npj Quantum Information 3, 34 (2017) Nature 555, 633 (2018) Science 359, 1123 (2018) Phys. Rev. X 9, 021011 (2019) Nature 579, 528 (2020) Nature 580, 355 (2020) OTHER LINKS: Vandersypen Lab: qutech.nl/vandersypen-lab/ Delft University of Technology: https://www.tudelft.nl/

During this time of lockdown, the centre for quantum software and information (QSI) at the University of Technology Sydney has launched an online seminar series. With talks once or twice a week from leading researchers in the field, meQuanics is supporting this series by mirroring the audio from each talk. I would encourage if you listen to this episode, to visit and subscribe to the UTS:QSI YouTube page to see each of these talks with the associated slides to help it make more sense. https://youtu.be/rOKpLd4X9jE Finding the ground state of the Hubbard model using hybrid quantum-classical computing. TITLE: Strategies for solving the Fermi-Hubbard model on near-term quantum computers SPEAKER: Lana Mineh AFFILIATION: Quantum Engineering Technology Labs, University of Bristol, UK HOSTED BY: Prof Michael Bremner, UTS Centre for Quantum Software and Information ABSTRACT: The Fermi-Hubbard model is of fundamental importance in condensed-matter physics, yet is extremely challenging to solve numerically. Finding the ground state of the Hubbard model using variational methods has been predicted to be one of the first applications of near-term quantum computers. Here we carry out a detailed analysis and optimisation of the complexity of variational quantum algorithms for finding the ground state of the Hubbard model, including costs associated with mapping to a real-world hardware platform. The depth complexities we find are substantially lower than previous work. We performed extensive numerical experiments for systems with up to 12 sites. The results suggest that the variational ansätze we used -- an efficient variant of the Hamiltonian Variational ansatz and a novel generalisation thereof -- will be able to find the ground state of the Hubbard model with high fidelity in relatively low quantum circuit depth. Our experiments include the effect of realistic measurements and depolarising noise. If our numerical results on small lattice sizes are representative of the somewhat larger lattices accessible to near-term quantum hardware, they suggest that optimising over quantum circuits with a gate depth less than a thousand could be sufficient to solve instances of the Hubbard model beyond the capacity of classical exact diagonalisation. RELATED ARTICLES: Strategies for solving the Fermi-Hubbard model on near-term quantum computers: https://arxiv.org/abs/1912.06007 OTHER LINKS: Quantum Engineering Technology Labs: bristol.ac.uk/qet-labs

During this time of lockdown, the centre for quantum software and information (QSI) at the University of Technology Sydney has launched an online seminar series. With talks once or twice a week from leading researchers in the field, meQuanics is supporting this series by mirroring the audio from each talk. I would encourage if you listen to this episode, to visit and subscribe to the UTS:QSI YouTube page to see each of these talks with the associated slides to help it make more sense. https://youtu.be/a5aa-vU2AHo Controls and frames: A new approach to quantum noise spectroscopy TITLE: Noise Cancellation and your Quantum Computer SPEAKER: Dr Gerardo Paz Silva AFFILIATION: Centre for Quantum Dynamics, Griffith University, Brisbane, Qld, Australia HOSTED BY: A/Prof Chris Ferrie, UTS Centre for Quantum Software and Information ABSTRACT: Noise cancellation, as in everyday headphones, requires the ability to characterize & filter out the noise affecting a system one wants to protect. The last few years have seen the birth of increasingly more powerful Quantum Noise Spectroscopy (QNS) protocols, capable of characterizing the noise affecting a quantum system of interest. However, while many of these protocols have been experimentally verified, all demonstrations have been so far limited to characterizing injected noise. More importantly, even theoretically a fully general protocol is still non-existent. In this talk I will introduce our new approach to the problem, which overcomes these limitations. I will argue that by characterizing only the portions of the noise that are relevant a given set of control capabilities, e.g., available to a particular experiment, many of the existing difficulties in designing a fully general QNS protocol disappear. I describe the key ingredients allowing this and exemplify our results via two paradigmatic examples. OTHER LINKS: Centre for Quantum Dynamics, Griffith University griffith.edu.au/centre-quantum-dynamics

During this time of lockdown, the centre for quantum software and information (QSI) at the University of Technology Sydney has launched an online seminar series. With talks once or twice a week from leading researchers in the field, meQuanics is supporting this series by mirroring the audio from each talk. I would encourage if you listen to this episode, to visit and subscribe to the UTS:QSI YouTube page to see each of these talks with the associated slides to help it make more sense. https://youtu.be/7wbK_9Sjnv8 Protecting and leveraging quantum machine learning algorithms on a future quantum internet TITLE: Introducing Adversarial Quantum Learning: Security and machine learning on the quantum internet SPEAKER: Assistant Professor Nana Liu AFFILIATION: Shanghai Jiao Tong University, PR China HOSTED BY: A/Prof Chris Ferrie, UTS Centre for Quantum Software and Information ABSTRACT: In the classical world, there is a powerful interplay between security and machine learning deployed in a network, like on the modern internet. What happens when the learning algorithms and the network itself can be quantum? What are the new problems that can arise and can quantum resources offer advantages to their classical counterparts? We explore these questions in a new area called adversarial quantum learning, that combines the area of adversarial machine learning, which investigates security questions in machine learning, and quantum information. For the first part of the talk, I’ll introduce adversarial machine learning and some exciting potential prospects for contributions from quantum information and computation. For the second part of the talk, I’ll present two new works on adversarial quantum learning. Here we are able to quantify the vulnerability of quantum algorithms for classification against adversaries and learn how to leverage quantum noise to improve its robustness against attacks. RELATED ARTICLES: Vulnerability of quantum classification to adversarial perturbations: https://arxiv.org/abs/1905.04286Quantum noise protects quantum classifiers against adversaries: https://arxiv.org/abs/2003.09416 OTHER LINKS: nanaliu.weebly.com/

During this time of lockdown, the centre for quantum software and information (QSI) at the University of Technology Sydney has launched an online seminar series. With talks once or twice a week from leading researchers in the field, meQuanics is supporting this series by mirroring the audio from each talk. I would encourage if you listen to this episode, to visit and subscribe to the UTS:QSI YouTube page to see each of these talks with the associated slides to help it make more sense. https://youtu.be/qYuxOx4Z8Yk A growing methodological problem for practical quantum algorithms research TITLE: Why are quantum algorithms papers so #!@*&% long? SPEAKER: Dr Yuval Sanders AFFILIATION: Centre for Quantum Software and Information, University of Technology Sydney ABSTRACT: In this talk I discuss the results of two of my recent quantum algorithms papers: arXiv:2007.07391 and arXiv:2110.05708. Both of these papers are 70+ pages in length and quite dense, which needs some explanation because the underlying ideas are not particularly complicated. The reason for the length is that we, the authors, are effectively compiling quantum algorithms by hand, and we are doing a very crude job of it. I will explain that increasing paper lengths are evidence for a growing methodological problem for practical quantum algorithms research. I will also explain why that methodological problem is in large part responsible to ongoing mistakes in media when attempting to articulate the real-world applications of quantum computers. HOSTED BY: Associate Professor Troy Lee, Centre for Quantum Software and Information, University of Technology Sydney, Australia RELATED PAPERS: https://arxiv.org/abs/2007.07391; https://arxiv.org/abs/2110.05708

During this time of lockdown, the centre for quantum software and information (QSI) at the University of Technology Sydney has launched an online seminar series. With talks once or twice a week from leading researchers in the field, meQuanics is supporting this series by mirroring the audio from each talk. I would encourage if you listen to this episode, to visit and subscribe to the UTS:QSI YouTube page to see each of these talks with the associated slides to help it make more sense. https://youtu.be/OfY7lFIBTGY Self-Guided Quantum Learning: Estimation via optimisation applied to quantum estimation TITLE: Self-Guided Quantum Learning SPEAKER: Associate Professor Chris Ferrie AFFILIATION: Centre for Quantum Software and Information, University of Technology Sydney, Australia HOSTED BY: Dr Clara Javaherian, UTS Centre for Quantum Software and Information, Australia ABSTRACT: Quantum state learning is often understood as a data analytics problem—large amounts of data collected from many prior repetitions of incompatible measurements need to be churned into a single estimate of a quantum state or channel. In this talk, I will present an adaptive optimisation algorithm which achieves the same goal, but at a drastic reduction in time and space complexity. RELATED ARTICLES: Experimental realization of self-guided quantum process tomography: https://arxiv.org/abs/1908.01082Experimental Demonstration of Self-Guided Quantum Tomography: https://arxiv.org/abs/1602.04194Self-guided quantum tomography: https://arxiv.org/abs/1406.4101 OTHER LINKS: Chris Ferrie: csferrie.com/

During this time of lockdown, the centre for quantum software and information (QSI) at the University of Technology Sydney has launched an online seminar series. With talks once or twice a week from leading researchers in the field, meQuanics is supporting this series by mirroring the audio from each talk. I would encourage if you listen to this episode, to visit and subscribe to the UTS:QSI YouTube page to see each of these talks with the associated slides to help it make more sense. https://youtu.be/L_VldJN_k-4 Bosonic mode error correcting codes: Quantum oscillators with an infinite Hilbert space TITLE: Quantum computing with rotation-symmetric bosonic codes SPEAKER: Assistant Professor Josh Combes AFFILIATION: University of Colorado Boulder, CO, USA HOSTED BY: A/Prof Chris Ferrie, UTS Centre for Quantum Software and Information ABSTRACT: Bosonic mode error correcting codes are error correcting codes where a qubit (or qudit) is encoded into one or multiple bosonic modes, i.e., quantum oscillators with an infinite Hilbert space. In the first part of this talk I will give an introduction codes that have a phase space translation symmetry, i.e. the Gottesman-Kitaev-Preskill aka GKP, and codes that obey a rotation symmetry. Moreover, I will survey the impressive experimental progress on these codes. The second part of the talk I focus on single-mode codes that obey rotation symmetry in phase space, such as the the well known Cat and Binomial codes. I will introduce a universal scheme for this class of codes based only on simple and experimentally well-motivated interactions. The scheme is fault-tolerant in the sense that small errors are guaranteed to remain small under the considered gates. I will also introduce a fault-tolerant error correction scheme based on cross-Kerr interactions and imperfect destructive phase measurement (e.g., a marginal of heterodyne). Remarkably, the error correction scheme approaches the optimal recovery map for Cat and Binomial codes when the auxiliary modes are error free. We numerically compute break-even thresholds under loss and dephasing, with ideal auxiliary systems. If time permits I will discuss the search for optimized codes and progress towards genuine fault tolerance. Joint work with Arne Grimsmo, USyd and Ben Baragiola, RMIT

During this time of lockdown, the centre for quantum software and information (QSI) at the University of Technology Sydney has launched an online seminar series. With talks once or twice a week from leading researchers in the field, meQuanics is supporting this series by mirroring the audio from each talk. I would encourage if you listen to this episode, to visit and subscribe to the UTS:QSI YouTube page to see each of these talks with the associated slides to help it make more sense. https://youtu.be/Vq8itsMG39w This talk explains the quantum supremacy milestone achieved by Google. TITLE: Quantum supremacy using a programmable superconducting processor SPEAKER: Prof Sergio Boixo AFFILIATION: Google Research, Los Angeles, USA HOSTED BY: Prof Michael Bremner, UTS Centre for Quantum Science and Information ABSTRACT: The promise of quantum computers is that certain computational tasks might be executed exponentially faster on a quantum processor than on a classical processor. A fundamental challenge is to build a high-fidelity processor capable of running quantum algorithms in an exponentially large computational space. Here we report the use of a processor with programmable superconducting qubits to create quantum states on 53 qubits, corresponding to a computational state-space of dimension 2^53 (about 10^16). Measurements from repeated experiments sample the resulting probability distribution, which we verify using classical simulations. Our Sycamore processor takes about 200 seconds to sample one instance of a quantum circuit a million times—our benchmarks currently indicate that the equivalent task for a state-of-the-art classical supercomputer would take approximately 10,000 years. This dramatic increase in speed compared to all known classical algorithms is an experimental realization of quantum supremacy for this specific computational task, heralding a much-anticipated computing paradigm.

During this time of lockdown, the centre for quantum software and information (QSI) at the University of Technology Sydney has launched an online seminar series. With talks once or twice a week from leading researchers in the field, meQuanics is supporting this series by mirroring the audio from each talk. I would encourage if you listen to this episode, to visit and subscribe to the UTS:QSI YouTube page to see each of these talks with the associated slides to help it make more sense. https://youtu.be/3OS7Pq6JoDY Q#, a quantum-focused domain-specific language explicitly designed to correctly, clearly and completely express quantum algorithms. TITLE: Empowering Quantum Machine Learning Research with Q# SPEAKER: Dr Christopher Granade AFFILIATION: Quantum Systems, Microsoft, Washington, USA HOSTED BY: A/Prof Chris Ferrie, UTS Centre for Quantum Software and Information ABSTRACT: In this talk, I will demonstrate how the Q# quantum programming language can be used to start exploring quantum machine learning, using a binary classification problem as an example. I will describe recent work in QML algorithms for classification, and show how Q# allows implementing and using this classifier through high-level quantum development features. Finally, I will discuss how these approaches can be used as part of a reproducible research process to share your explorations with others.

During this time of lockdown, the centre for quantum software and information (QSI) at the University of Technology Sydney has launched an online seminar series. With talks once or twice a week from leading researchers in the field, meQuanics is supporting this series by mirroring the audio from each talk. I would encourage if you listen to this episode, to visit and subscribe to the UTS:QSI YouTube page to see each of these talks with the associated slides to help it make more sense. https://youtu.be/8Cmw5u8fazk TITLE: Spooky complexity at a distance SPEAKER: Prof Zhengfeng Ji AFFILIATION: UTS Centre for Quantum Software and Information, Sydney, Australia HOSTED BY: Prof Sven Rogge, Centre for Quantum Computation & Communication Technology (CQC2T) ABSTRACT: In this talk, I will discuss the recent result on the characterisation of the power of quantum multi-prover interactive proof systems, MIP*=RE. After a brief setup of the problem, we will highlight its rich connections and implications to problems in computer science, quantum physics, and mathematics, including the Tsirelson's problem and Connes' embedding problem. In the second half of the talk, we will outline the overall proof strategy and introduce several key techniques employed in the proof. RELATED ARTICLES: MIP*=RE: https://arxiv.org/abs/2001.04383

During this time of lockdown, the centre for quantum software and information (QSI) at the University of Technology Sydney has launched an online seminar series. With talks once or twice a week from leading researchers in the field, meQuanics is supporting this series by mirroring the audio from each talk. I would encourage if you listen to this episode, to visit and subscribe to the UTS:QSI YouTube page to see each of these talks with the associated slides to help it make more sense. https://youtu.be/jrUpFdUQ6A4 Building a bigger Hilbert space for superconducting devices, one Bloch state at a time. TITLE: A new kind of qubit SPEAKER: Prof Tom Stace AFFILIATION: School of Mathematics and Physics, University of Queensland HOSTED BY: A/Prof. Nathan Langford, UTS Centre for Quantum Software and Information ABSTRACT: Noise and errors have been the bottlenecks for building robust quantum machines. I will describe a proposed new class of superconducting devices that has built-in error rejection. Fundamentally, the encoding that facilitates this intrinsic robustness comes from the recognition that the Bloch band structure of these systems leads to a much bigger Hilbert spaces than has been traditionally considered. The extra space affords new qubit encodings, which I describe in two different instantiations. OTHER LINKS: Prof Tom Stace University Profile - researchers.uq.edu.au/researcher/1636

During this time of lockdown, the centre for quantum software and information (QSI) at the University of Technology Sydney has launched an online seminar series. With talks once or twice a week from leading researchers in the field, meQuanics is supporting this series by mirroring the audio from each talk. I would encourage if you listen to this episode, to visit and subscribe to the UTS:QSI YouTube page to see each of these talks with the associated slides to help it make more sense. https://youtu.be/sUANYeTrmHQ A scalable tomography for fermonic systems. TITLE: A Scalable Fermion Measurement SPEAKER: Dr Chris Jackson AFFILIATION: Center for Quantum Information and Control (CQulC), University of New Mexico, Albuquerque, NM | UTS Centre for Quantum Software and Information, Sydney, Australia HOSTED BY: A/Prof. Chris Ferrie, UTS Centre for Quantum Software and Information ABSTRACT: Fermion systems have a Hilbert space dimension that scales exponentially in the number of modes. Standard tomography thus says that to completely measure an unknown state would require the measurement of exponentially many observables. However, if the parity of a fermion state is known, then there exists a nonadaptive, tomographically complete continuous measurement which only requires the isotropic measurement of quadratically many observables. The effects of the corresponding POVM are the well known superconducting Bardeen-Cooper-Schrieffer (BCS) coherent states. The BCS coherent states define a manifold which can be used as a phase space to represent fermion quantum information. In this talk, I will introduce the BCS-coherent state POVM, explain the isotropic measurement which implements it, and discuss the geometry of the corresponding phase space. OTHER LINKS: Centre for Quantum Information & Control: https://cquic.unm.edu/

During this time of lockdown, the centre for quantum software and information (QSI) at the University of Technology Sydney has launched an online seminar series. With talks once or twice a week from leading researchers in the field, meQuanics is supporting this series by mirroring the audio from each talk. I would encourage if you listen to this episode, to visit and subscribe to the UTS:QSI YouTube page to see each of these talks with the associated slides to help it make more sense. https://youtu.be/XSJks4cRDv0 Cryptographic protocols for classical clients to verifiably delegate quantum computation to untrusted quantum servers - the desiderata and their feasibility. TITLE: How well can a classical client delegate quantum computation? SPEAKER: Dr Kai-Min Chung AFFILIATION: Institute of Information Science, Academia Sinica, Taiwan HOSTED BY: Prof Zhengfeng Ji, UTS Centre for Quantum Software and Information ABSTRACT: In a recent breakthrough, Mahadev (FOCS 2018) constructed the first classical verification of quantum computation (CVQC) protocol that allows a classical client to delegate the computation of a BQP language (i.e., a decision problem) to an efficient quantum server. In this talk, we present several generalizations of Mahadev’s work. In particular, we initiate the study of CVQC protocols for quantum *sampling* problems and construct the first such protocol that allows a classical client to verifiably obtain a sample drawn from a quantum computation from a quantum server. We also construct the first protocol with efficient verification, i.e., the client’s runtime can be sublinear in the quantum time complexity of the delegated computation. Finally, we present a generic compiler that compiles any CVQC protocol to achieve blindness, i.e., the server learns nothing about the client’s input, which leads to the first constant-round blind CVQC protocol. Based on joint works with Nai-Hui Chia, Takashi Yamakawa, Yi Lee, Han-Husan Lin, and Xiaodi Wu REFERENCES: Classical Verification of Quantum Computations with Efficient Verifier: https://arxiv.org/abs/1912.00990

During this time of lockdown, the centre for quantum software and information (QSI) at the University of Technology Sydney has launched an online seminar series. With talks once or twice a week from leading researchers in the field, meQuanics is supporting this series by mirroring the audio from each talk. I would encourage if you listen to this episode, to visit and subscribe to the UTS:QSI YouTube page to see each of these talks with the associated slides to help it make more sense. https://youtu.be/yAUSMUYfXlU So you want to build a useful quantum computer… where to begin?! TITLE: Building Google’s Quantum Computer SPEAKER: Dr Marissa Giustina AFFILIATION: Google AI Quantum, Google Research, CA, USA HOSTED BY: A/Prof Nathan Langford, UTS Centre for Quantum Software and Information ABSTRACT: The Google AI Quantum team develops chip-based circuitry that one can interact with (control and read out) and which behaves reliably according to a simple quantum model. Such quantum hardware holds promise as a platform for tackling problems intractable to classical computing hardware. While the demonstration of a universal, fault-tolerant, quantum computer remains a goal for the future, it has informed the design of a prototype with which we have recently controlled a quantum system of unprecedented scale. This talk introduces Google’s quantum computing effort from both hardware and quantum-information perspectives, including an overview of recent technological developments and some recent results. RELATED ARTICLES: Quantum supremacy using a programmable superconducting processor:

During this time of lockdown, the centre for quantum software and information (QSI) at the University of Technology Sydney has launched an online seminar series. With talks once or twice a week from leading researchers in the field, meQuanics is supporting this series by mirroring the audio from each talk. I would encourage if you listen to this episode, to visit and subscribe to the UTS:QSI YouTube page to see each of these talks with the associated slides to help it make more sense. https://www.youtube.com/watch?v=N1We-MpoJlM&t=5s SEMINAR 1 TITLE: Understanding Crosstalk in Quantum Processors SPEAKER: A/Prof Robin Blume-Kohout AFFILIATION: Quantum Performance Lab, Sandia National Laboratories, Albuquerque, New Mexico HOSTED BY: A/Prof Chris Ferrie, UTS Centre for Quantum Software and Information ABSTRACT: Multi-qubit quantum processors fail – i.e., deviate from ideal behavior – in many ways. One of the most important, especially as the number of qubits grows, is crosstalk. But “crosstalk” refers to a wide range of distinct phenomena. In this talk, I will present a precise and rigorous framework that we have developed for defining and classifying crosstalk errors, and compare it to existing ad hoc definitions. Then, I will present two protocols that we are deploying to detect and characterize crosstalk, and show how we are using them to break down and demystify the error behavior of testbed-class quantum processors in the wild. SEMINAR 2 TITLE: Hold the onion: using fewer circuits to characterize your qubits SPEAKER: Dr Erik Nielsen AFFILIATION: Quantum Performance Lab, Sandia National Laboratories, Albuquerque, New Mexico HOSTED BY: A/Prof Chris Ferrie, UTS Centre for Quantum Software and Information ABSTRACT: Model-based quantum tomography protocols like gate set tomography optimize a noise model with some number of parameters in order to fit experimental data. As the number of qubits increases, two issues emerge: 1) the number of model parameters grows, and 2) the cost of propagating quantum states (density matrices) increases exponentially. The first issue can be addressed by considering reduced models that limit errors to being low-weight and geometrically local. In this talk, we focus on the second issue and present a method for performing approximate density matrix propagation based on perturbative expansions of error generators. The method is tailored to the likelihood optimization problem faced by model-based tomography protocols. We will discuss the advantages and drawbacks of using this method when characterizing the errors in up to 8-qubit systems.

During this time of lockdown, the centre for quantum software and information (QSI) at the University of Technology Sydney has launched an online seminar series. With talks once or twice a week from leading researchers in the field, meQuanics is supporting this series by mirroring the audio from each talk. I would encourage if you listen to this episode, to visit and subscribe to the UTS:QSI YouTube page to see each of these talks with the associated slides to help it make more sense. Building better deep learning representations for quantum mixed states by adding quantum layers to classical probabilistic models. TITLE: Quantum-probabilistic Generative Models and Variational Quantum Thermalization SPEAKER: Guillaume Verdon AFFILIATION: X (formerly Google X), California, USA HOSTED BY: A/Prof. Chris Ferrie, Centre for Quantum Software and Information ABSTRACT: We introduce a new class of generative quantum-neural-network-based models called Quantum Hamiltonian-Based Models (QHBMs). In doing so, we establish a paradigmatic approach for quantum-probabilistic hybrid variational learning of quantum mixed states, where we efficiently decompose the tasks of learning classical and quantum correlations in a way which maximizes the utility of both classical and quantum processors. In addition, we introduce the Variational Quantum Thermalizer (VQT) algorithm for generating the thermal state of a given Hamiltonian and target temperature, a task for which QHBMs are naturally well-suited. The VQT can be seen as a generalization of the Variational Quantum Eigensolver (VQE) to thermal states: we show that the VQT converges to the VQE in the zero temperature limit. We provide numerical results demonstrating the efficacy of these techniques in several illustrative examples. In addition to the introduction to the theory and applications behind these models, we will briefly walk through their numerical implementation in TensorFlow Quantum. RELATED ARTICLES: Quantum Hamiltonian-Based Models and the Variational Quantum Thermalizer Algorithm: https://arxiv.org/abs/1910.02071 TensorFlow Quantum: A Software Framework for Quantum Machine Learning: https://arxiv.org/abs/2003.02989 OTHER LINKS: X: https://x.company/

During this time of lockdown, the centre for quantum software and information (QSI) at the University of Technology Sydney has launched an online seminar series. With talks once or twice a week from leading researchers in the field, meQuanics is supporting this series by mirroring the audio from each talk with an exclusive 10min interview with each of our presenters. I would encourage if you listen to this episode, to visit and subscribe to the UTS:QSI YouTube page to see each of these talks with the associated slides to help it make more sense. Click the link below to see the talk uploaded to the meQuanics podcast from Daniel Grier from the University of Waterloo and the Institute for Quantum Computing. https://www.youtube.com/watch?v=El7JAmvUQ1U

During this time of lockdown, the centre for quantum software and information (QSI) at the University of Technology Sydney has launched an online seminar series. With talks once or twice a week from leading researchers in the field, meQuanics is supporting this series by mirroring the audio from each talk with an exclusive 10min interview with each of our presenters. I would encourage if you listen to this episode, to visit and subscribe to the UTS:QSI YouTube page to see each of these talks with the associated slides to help it make more sense. Click the link below to see the talk uploaded to the meQuanics podcast from Maria Schuld from Xanadu and the University of Kwazulu Natal. https://www.youtube.com/watch?v=RKdFNJtTeeA