# Video Library

Since 2002 Perimeter Institute has been recording seminars, conference talks, public outreach events such as talks from top scientists using video cameras installed in our lecture theatres.  Perimeter now has 7 formal presentation spaces for its many scientific conferences, seminars, workshops and educational outreach activities, all with advanced audio-visual technical capabilities.

Recordings of events in these areas are all available and On-Demand from this Video Library and on Perimeter Institute Recorded Seminar Archive (PIRSA)PIRSA is a permanent, free, searchable, and citable archive of recorded seminars from relevant bodies in physics. This resource has been partially modelled after Cornell University's arXiv.org.

Accessibly by anyone with internet, Perimeter aims to share the power and wonder of science with this free library.

## Stabilizer codes for prime power qudits

Thursday Nov 28, 2019
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There is a standard generalization of stabilizer codes to work with qudits which have prime dimension, and a slightly less standard generalization for qudits whose dimension is a prime power. However, for prime power dimensions, the usual generalization effectively treats the qudit as multiple prime-dimensional qudits instead of one larger object. There is a finite field GF(q) with size equal to any prime power, and it makes sense to label the qudit basis states with elements of the finite field, but the usual stabilizer codes do not make use of the structure of the finite field.

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## Self-correction from symmetry

Thursday Nov 28, 2019
Speaker(s):

A self-correcting quantum memory can store and protect quantum information for a time that increases without bound in the system size, without the need for active error correction. Unfortunately, the landscape of Hamiltonians based on stabilizer (subspace) codes is heavily constrained by numerous no-go results and it is not known if they can exist in three dimensions or less. In this talk, we will discuss the role of symmetry in self-correcting memories.

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## PSI 2019/2020 - Quantum Field Theory II (David) - Lecture 11

Thursday Nov 28, 2019
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## Towards local testability for quantum coding

Wednesday Nov 27, 2019
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We introduce the hemicubic codes, a family of quantum codes obtained by associating qubits with the

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## A computationally universal phase of quantum matter

Wednesday Nov 27, 2019
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We provide the first example of a symmetry protected quantum phase that has universal computational power. Throughout this phase, which lives in spatial dimension two, the ground state is a universal resource for measurement based quantum computation. Joint work with Cihan Okay, Dong-Sheng Wang, David T. Stephen, Hendrik Poulsen Nautrup; J-ref: Phys. Rev. Lett. 122, 090501

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## Fine-grained quantum supremacy and stabilizer rank

Wednesday Nov 27, 2019
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It is known that several sub-universal quantum computing models cannot be classically simulated unless the polynomial-time
hierarchy collapses. However, these results exclude only polynomial-time classical simulations. In this talk, based on fine-grained
complexity conjectures, I show more fine-grained" quantum supremacy results that prohibit certain exponential-time classical simulations.
I also show the stabilizer rank conjecture under fine-grained complexity conjectures.

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## The Cohomology of Groups (Johnson-Freyd/Guo) - Lecture 9

Wednesday Nov 27, 2019
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## Classical algorithms for quantum mean values

Wednesday Nov 27, 2019
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Consider the task of estimating the expectation value of an n-qubit tensor product observable in the output state of a shallow quantum circuit. This task is a cornerstone of variational quantum algorithms for optimization, machine learning, and the simulation of quantum many-body systems. In this talk I will describe three special cases of this problem which are "easy" for classical computers. This is joint work with Sergey Bravyi and Ramis Movassagh.

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## PSI 2019/2020 - Quantum Field Theory II (David) - Lecture 10

Wednesday Nov 27, 2019
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## Magic resource theories and classical simulation

Tuesday Nov 26, 2019
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I will review the stabiliser rank and associated pure state magic monotone, the extent, [Bravyi et. al 2019]. Then I will discuss several new magic monotones that can be regarded as a generalisation of the extent monotone to mixed states [Campbell et. al., in preparation]. My talk will outline several nice theorems we can prove about these monotones relate to each other and how they are related to the runtime of new classical simulation algorithms.

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## Lectures On-Demand

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