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Time: Australian Eastern Daylight Time (AEDT), or local Sydney time.
Monday 7 December
11:00 – 12:00
INVITED TALK 1
Session Chair: Stephen Bartlett, University of Sydney, Australia
Speaker: Nicole Yunger Halpern
Affiliation: Harvard-Smithsonian ITAMP (Institute for Theoretical Atomic, Molecular, and Optical Physics) | Harvard University Department of Physics | MIT Research Lab of Electronics and Center for Theoretical Physics
Title: Noncommuting conserved quantities in thermalization
Abstract:
In statistical mechanics, a small system exchanges conserved quantities—heat, particles, electric charge, etc.—with a bath. The small system may thermalize to the canonical ensemble, the grand canonical ensemble, etc. The conserved quantities are represented by operators usually assumed to commute with each other. But noncommutation distinguishes quantum physics from classical. What if the operators fail to commute? Quantum-information-theoretic thermodynamics has recently been used to argue that the small system thermalizes to near a “non-Abelian thermal state.” I will present a protocol for realizing this state experimentally, supported with numerical simulations of a spin chain. The protocol is suited to ultracold atoms, trapped ions, quantum dots, and more. This work introduces a nonclassical phenomenon—noncommutation of conserved quantities—into a decades-old thermodynamics problem.
12:00 – 13:30
RESEARCH TOPIC 1: CRYPTO
The research topic sessions offer a very casual space to ‘mingle’ and chat. The purpose of the session is:
– to engage with the paper presenters of the specific topic area and to discuss or ask questions relating to their paper.
– to recreate some of the in-person experience of a conference: discussions about the talks and new topics, networking, forging and maintaining collaborations, and generally having a friendly, and collegial experience during and in between talks.
13:30 – 14:30
INVITED TALK 2
Session Chair: Isaac Kim, University of Sydney, Australia
Speaker: Patrick Coles
Affiliation: Los Alamos National Laboratory (LANL), USA
Title: Promises and Challenges of Variational Quantum Algorithms
Abstract:
Beyond finding ground states, new applications have recently emerged for Variational Quantum Algorithms (VQAs). These include dynamical simulation, metrology, solving linear systems, and principal component analysis, among others. Moreover, new tools are making VQAs more feasible, such as quantum-aware optimizers and error mitigation methods. VQAs also exhibit an intriguing resilience to certain types of noise. These signs point to VQAs soon providing quantum advantage for practically interesting problems. On the flip side, new analytical results have studied the gradient scaling for VQAs. These results paint a concerning picture, and show that barren plateaus in the training landscape will emerge if care is not taken. Barren plateaus are caused by lack of structure or simply by the presence of noise. Avoiding barren plateaus has now become a crucial area of research. This talk will review both the exciting and challenging nature of VQAs for near-term quantum computing.
14:30 – 15:30 SESSION BREAK
15:30 – 16:30
INVITED TALK 3
Session Chair: Keisuke Fujii, Division of Advanced Electronics and Optical Science, Osaka University, Japan
Speaker: Francesco Buscemi
Affiliation: Nagoya University, Japan
Title: Statistical tests of “quantumness'”: from mathematics to technology
Abstract:
With the ever increasing expectations surrounding quantum technologies, a basic question common to a variety of areas within quantum information science is to characterize the divide between classical (i.e., classically simulable) and quantum (i.e., genuinely beyond classical theory) devices, and to provide criteria to certify and benchmark the “degree of quantumness” of any given device. Certainly such a question is intrinsically multifaceted and admits many (often inequivalent) approaches. In this talk I will focus on statistical tests of various embodiments of quantumness, ranging from bipartite resources to quantum memories and measurements, keeping in mind however a unified conceptual framework, that I identify in the theory of “statistical comparisons” from mathematical statistics.
16:30 – 18:00
RESEARCH TOPIC 2: RESOURCES
The research topic sessions offer a very casual space to ‘mingle’ and chat. The purpose of the session is:
– to engage with the paper presenters of the specific topic area and to discuss or ask questions relating to their paper.
– to recreate some of the in-person experience of a conference: discussions about the talks and new topics, networking, forging and maintaining collaborations, and generally having a friendly, and collegial experience during and in between talks.
18:00 – 19:00
INVITED TALK 4
Session Chair: Marco Tomamichel, National University of Singapore, Singapore
Speaker: Nilanjana Datta
Affiliation: University of Cambridge, UK
Title: Perfect discrimination of unitary channels and novel quantum speed limits
Abstract:
Discriminating between unknown objects in a given set is a fundamental task in experimental science. Suppose you are given a quantum system which is in one of two given states with equal probability. Determining the actual state of the system amounts to doing a measurement on it which would allow you to discriminate between the two possible states. It is known that unless the two states are mutually orthogonal, perfect discrimination is possible only if you are given arbitrarily many identical copies of the state.
In this talk we consider the task of discriminating between quantum channels, instead of quantum states. In particular, we discriminate between a pair of unitary channels acting on a quantum system whose underlying Hilbert space is infinite-dimensional. We prove that in contrast to state discrimination, one only needs a finite number of uses of these channels in order to discriminate perfectly between them. Furthermore, no entanglement is needed in the discrimination task. The measure of discrimination is given in terms of the energy-constrained diamond norm, and a key ingredient of the proofs of these results is a generalization of the Toeplitz-Hausdorff Theorem of convex analysis . Moreover, we employ our results to study a novel type of quantum speed limits which apply to pairs of quantum evolutions. This work was done jointly with Simon Becker (Cambridge), Ludovico Lami (Ulm) and Cambyse Rouze (Munich).
Tuesday 8 December
11:00 – 12:00
INVITED TALK 5
Session Chair: Ben Brown, University of Sydney, Australia
Speaker: Aleksander Kubica
Affiliation: Perimeter Institute for Theoretical Physics, Canada
Title: Using Quantum Metrological Bounds in Quantum Error Correction: A Simple Proof of the Approximate Eastin-Knill Theorem
Abstract: We present a simple proof of the approximate Eastin-Knill theorem, which connects the quality of a quantum error-correcting code (QECC) with its ability to achieve a universal set of transversal logical gates. Our derivation employs powerful bounds on the quantum Fisher information in generic quantum metrological protocols to characterize the QECC performance measured in terms of the worst-case entanglement fidelity. The theorem is applicable to a large class of decoherence models, including independent erasure and depolarizing noise. Our approach is unorthodox, as instead of following the established path of utilizing QECCs to mitigate noise in quantum metrological protocols, we apply methods of quantum metrology to explore the limitations of QECCs.
12:00 – 13:30
RESEARCH TOPIC 3: INFORMATION THEORY
The research topic sessions offer a very casual space to ‘mingle’ and chat. The purpose of the session is:
– to engage with the paper presenters of the specific topic area and to discuss or ask questions relating to their paper.
– to recreate some of the in-person experience of a conference: discussions about the talks and new topics, networking, forging and maintaining collaborations, and generally having a friendly, and collegial experience during and in between talks.
13:30 – 14:30
INVITED TALK 6
Session Chair: Yuval Sanders, Macquarie University, Australia
Speaker: François Le Gall
Affiliation: Nagoya University, Japan
Title: Average-Case Quantum Advantage with Shallow Circuits
Abstract: In 2018, Bravyi, Gosset and König proved an unconditional separation between the computational powers of small-depth quantum and classical circuits for a relation. In this talk I will describe similar separations that give even stronger evidence of the superiority of small-depth quantum computation. The first part of the talk will describe the average-case separation from ArXiv:1810.12792, which constructs a computational task that can be solved on all inputs by a quantum circuit of constant depth with bounded-fanin gates (a “shallow” quantum circuit) and shows that any classical circuit with bounded-fanin gates solving this problem on a non-negligible fraction of the inputs must have logarithmic depth. The second part of the talk will discuss further recent developments.
14:30 – 15:30 SESSION BREAK
15:30 – 16:30
INVITED TALK 7
Session Chair: Francesco Buscemi, Nagoya University, Japan
Speaker: Qiang Zhang
Affiliation: University of Science and Technology of China (USTC), China
Title: Recent experimental progress in quantum key distribution
Abstract:
Quantum key distribution (QKD) together with one time pad encoding can provide unconditional secure communication. Tremendous theoretical and experimental efforts have taken place in the field. However, the transmission distance and the security with imperfect devices are still bottle necks for its wide applications. Here, I shall review the research focusing on these bottlenecks and especially introduce the very recent results by our group, including twin field QKD experiment over 500 km deployed fiber, the first free space MDI-QKD and so on.
16:30 – 18:00
RESEARCH TOPIC 4: COMMUNICATION
The research topic sessions offer a very casual space to ‘mingle’ and chat. The purpose of the session is:
– to engage with the paper presenters of the specific topic area and to discuss or ask questions relating to their paper.
– to recreate some of the in-person experience of a conference: discussions about the talks and new topics, networking, forging and maintaining collaborations, and generally having a friendly, and collegial experience during and in between talks.
18:00 – 19:00
INVITED TALK 8
Session Chair: Keisuke Fujii, Osaka University, Japan
Speaker: Takashi Yamamoto
Affiliation: Osaka University, Japan
Title: Quantum network with atoms and photons
Abstract:
I will discuss several experiments on elemental schemes for a quantum network with atoms and photons in this talk. I will introduce recent advances in quantum frequency conversion for translating a single photon frequency using a second-order nonlinear process in a waveguide periodically-poled lithium niobate (PPLN) crystal. Then I will show the applications to an atom-telecom photon quantum system built with atoms. Finally, I will show an experimental demonstration of an all-photonic quantum repeater.
Wednesday 9 December
11:00 – 12:00
INVITED TALK 9
Session Chair: Ben Brown, University of Sydney, Australia
Speaker: Michael Newman
Affiliation: Google, USA
Title: Fault-tolerant Operation of a Bacon-Shor Encoded Qubit
Abstract:
Many useful quantum algorithms require gate error rates on the order of one failure in one trillion. Fault-tolerant circuit design promises to realize such near-perfect operations with lower fidelity components at the cost of significant operational overhead. However, some devices have reached the sizes and accuracies necessary to test these benefits. In this talk, we will discuss fault-tolerant operation of a Bacon-Shor encoded qubit within a 15 ion chain. We will begin with a review of fault-tolerance, and then focus on the interplay between the choice of code and the device. To conclude, we will touch on some of the challenges beyond near-term demonstrations of error-correction, including detrimental noise sources and the significant classical co-processing required to decode errors at scale. The experiment is a collaboration between the University of Maryland and Duke University
Paper: arXiv:2009.11482
12:00 – 13:30
RESEARCH TOPIC 5: COMPUTATION
The research topic sessions offer a very casual space to ‘mingle’ and chat. The purpose of the session is:
– to engage with the paper presenters of the specific topic area and to discuss or ask questions relating to their paper.
– to recreate some of the in-person experience of a conference: discussions about the talks and new topics, networking, forging and maintaining collaborations, and generally having a friendly, and collegial experience during and in between talks.
13:30 – 14:30
INVITED TALK 10
Session Chair: Stephen Bartlett, University of Sydney, Australia
Speaker: Andrew Dzurak
Affiliation: UNSW Sydney, Australia
Title: Silicon-based quantum computing: The path from the laboratory to industrial manufacture
Abstract:
In this talk I will give an overview of the development of silicon-based quantum computing (QC), from the basic science through to its prospects for industrial-scale commercialization based on CMOS manufacturing. I begin with Kane’s original proposal [1] for a silicon quantum computer, conceived at UNSW in 1998, based on single donor atoms in silicon, and will review the first demonstrations of such qubits, using both electron spins [2,3] and nuclear spins [4]. I then discuss the development of SiMOS quantum dot qubits, including the demonstration of single-electron occupancy [5], high-fidelity single-qubit gates [6], and the first demonstration of a two-qubit logic gate in silicon [7], together with the most recent assessments of silicon qubit fidelities [9,10]. I will also explore the technical issues related to scaling a silicon-CMOS based quantum processor [8] up to the millions of qubits that will be required for fault-tolerant QC, including the recent demonstration of silicon qubit operation above one kelvin [11].
14:30 – 15:30 SESSION BREAK
15:30 – 16:30
INVITED TALK 11
Session Chair: Michael Bremner, University of Technology Sydney, Australia
Speaker: Zhengfeng Ji (15:30 – 16:30)
Affiliation: Centre for Quantum Software and Information, University of Technology Sydney, Australia
Title: Spooky complexity at a distance
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 (arXiv:2001.04383). 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.
Paper: arXiv:2001.04383
16:30 – 18:00
RESEARCH TOPIC 6: FUNDAMENTALS
The research topic sessions offer a very casual space to ‘mingle’ and chat. The purpose of the session is:
– to engage with the paper presenters of the specific topic area and to discuss or ask questions relating to their paper.
– to recreate some of the in-person experience of a conference: discussions about the talks and new topics, networking, forging and maintaining collaborations, and generally having a friendly, and collegial experience during and in between talks.
18:00 – 19:00
INVITED TALK 12
Session Chair: Mária Kieferová, University of Technology Sydney, Australia
Speaker: Da-Wei Wang
Affiliation: Zhejiang University, China
Title: Topological Phases of quantized light
Abstract:
Topological photonics is an emerging research area that focuses on the topological states of classical light. Here we reveal the topological phases that are intrinsic to the quantum nature of light, i.e., solely related to the quantized Fock states and the inhomogeneous coupling between them. The Hamiltonian of two cavities coupled with a two-level atom is an intrinsic one-dimensional Su-Schriefer-Heeger model of Fock states. By adding another cavity, the Fock-state lattice is extended to two dimensions with a honeycomb structure, where the strain due to the inhomogeneous coupling strengths of the annihilation operator induces a Lifshitz topological phase transition between a semimetal and three band insulators within the lattice. In the semimetallic phase, the strain is equivalent to a pseudomagnetic field, which results in the quantization of the Landau levels and the valley Hall effect. We further construct an inhomogeneous Fock-state Haldane model where the topological phases can be characterized by the topological markers. With d cavities being coupled to the atom, the lattice is extended to d-1 dimensions without an upper limit. This study demonstrates a fundamental distinction between the topological phases in quantum and classical optics and provides a novel platform for studying topological physics in dimensions higher than three.
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