Seminar: A/Prof Marco Tomamichel

Fault-tolerant quantum advantage with shallow circuits
As larger and larger prototypes of quantum computers are being developed, one of the most exciting challenges in the theory of quantum computing is to find computational problems that can be solved by an intermediate-scale noisy quantum computer

Research Fellowship Seminar Series 2019

Title: Fault-tolerant quantum advantage with shallow circuits

Abstract:
As larger and larger prototypes of quantum computers are being developed, one of the most exciting challenges in the theory of quantum computing is to find computational problems that can be solved by an intermediate-scale noisy quantum computer but are beyond the capabilities of existing non-quantum computers. Towards this goal, we construct a class of problems that show a weaker separation: they can be solved by noisy quantum computers of constant circuit depth but require at least logarithmic depth classical circuits.

Prior work has shown that there exists a related problem which can be solved with certainty by a constant-depth quantum circuit composed of geometrically local gates in two dimensions, but cannot be solved with high probability by any classical constant depth circuit composed of bounded fan-in gates. Here we provide two extensions of this result. Firstly, we show that a separation in computational power persists even when the constant-depth quantum circuit is restricted to geometrically local gates in one dimension. The corresponding quantum algorithm is the simplest we know of which achieves a quantum advantage of this type. It may also be more practical for future implementations.

Our second, main result, is that a separation persists even if the shallow quantum circuit is corrupted by noise. We construct a relation problem which can be solved with near certainty using a noisy constant-depth quantum circuit composed of geometrically local gates in three dimensions, provided the noise rate is below a certain constant threshold value. On the other hand, the problem cannot be solved with high probability by a noise-free classical circuit of constant-depth.

Bio:
Dr Marco Tomamichel's research expertise lies in the intersection of information theory, cryptography and quantum mechanics. His main focus is on the mathematical foundations of quantum information theory, for example, the study of entropy and other information measures, as well as theoretical questions that arise in quantum communication and cryptography when the available resources are limited.
He is currently an Associate Professor with the Centre for Quantum Software and Information (CQSI). He received his Master of Science degree from the Department of Electrical Engineering and Information Technology at ETH Zurich, and a doctorate in Theoretical Physics also from ETH Zurich. After that, he was a Research Fellow at the Centre for Quantum Technologies (CQT) in Singapore, where he continues to be engaged as a Visiting Researcher. Before joining UTS, he was University of Sydney Postdoctoral Fellow. He has received funding from the Australian Research Council (ARC) for a Discovery Early Career Researcher Award (DECRA).

Catering: a light lunch will be provided from 12:00pm - 12:15pm (the seminar will commence at 12:15pm)

Sponsored by: UTS Faculty of Engineering and IT
 

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