QSI Events - Professor Richard Jozsa, Cambridge

Richard Jozsa

Date: Monday 27th August - 12:00pm [light lunch will be provided]

Venue: CB11.6.408 [FEIT Seminar Room]

Speaker: Professor Richard Jozsa, University of Cambridge, UK.

Title: The Pauli based computing model and quantum advantage of unitary Clifford circuits with magic state inputs

Abstract: We study the computational power of unitary Clifford circuits with solely magic state inputs and only final Z basis measurements (called CM circuits), supplemented by classical efficient computation. We will begin by reviewing the so-called Pauli Based Computation model of Bravyi, Smith and Smolin, and show how this formalism leads to an extension of the Gottesman-Knill theorem, that applies to universal computation: for (generally adaptive) Clifford circuits with joint stabiliser and non-stabiliser inputs, the stabiliser part can be eliminated in favour of classical simulation, leaving a Clifford circuit on only the non-stabiliser part, from whose outputs (with classical post-processing) the original circuit can be sampled.

Using this result, we show that  CM circuits are hard to classically (weakly) simulate up to multiplicative error (assuming PH non-collapse), and also up to additive error under plausible average-case hardness conjectures. Unlike other such known classes, a broad variety of possible conjectures apply, any one of which suffices to imply hardness of classical simulation for CM circuits.

This is joint work with Mithuna Yoganathan and Sergii Strelchuk.    

Short bio: Professor Richard Jozsa is one of the founders of Quantum Information Science. He has made many ground-breaking contributions to the theory of quantum information and computation, including the   (co-) discoveries of quantum teleportation and the first quantum algorithm that is exponentially more efficient than any classical algorithm (the Deutsch-Jozsa algorithm). In recent years his research has focused on the computational complexity of simulations of quantum circuit families. The high standards of Professor Jozsa's work has been recognized by many international institutions, including the London Mathematical Society who awarded him the 2004 Naylor Prize and "Physics Today" who in 2005 named the teleportation paper as one of the ten hottest papers in their 110-year history. Currently, Professor Jozsa is the Leigh Trapnell Professor of Quantum Physics and head of the Centre for Quantum Information and Foundations within the Department of Applied Mathematics and Theoretical Physics at the University of Cambridge. He also serves on the editorial board of "Physical Review Letters", has been a member of steering committees for the major annual conferences "Quantum Information Processing" and the "Asian Quantum Information Science Conference", and was a founding managing editor of the journal of "Quantum Information and Computation". He is also a member of Advisory Board of UTS Centre for Quantum Software and Information and a partner investigator in the ARC Centre of Excellence for Quantum Computation and Communication Technology.

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