A A
Connect with us:

# Perimeter Institute Quantum Discussions

This series consists of weekly discussion sessions on foundations of quantum Theory and quantum information theory. The sessions start with an informal exposition of an interesting topic, research result or important question in the field. Everyone is strongly encouraged to participate with questions and comments.

## Seminar Series Events/Videos

Oct 24 2017 - 10:00am
Room #: 301
Speaker(s):
Scientific Areas:
Nov 29 2017 - 4:00pm
Room #: 405
Speaker(s):
Scientific Areas:

## Poking holes and cutting corners to achieve Clifford gates with the surface code

Wednesday Oct 18, 2017
Speaker(s):

The surface code is currently the leading proposal to achieve fault-tolerant quantum computation. Among its strengths are the plethora of known ways in which fault-tolerant Clifford operations can be performed, namely, by deforming the topology of the surface, by the fusion and splitting of codes, and even by braiding engineered Majorana modes using twist defects. Here, we present a unified framework to describe these methods, which can be used to better compare different schemes and to facilitate the design of hybrid schemes.

## Boundaries and Twists in the Color Code

Wednesday Oct 11, 2017
Speaker(s):

We present an in-depth study of the domain walls available in the color code. We begin by presenting new boundaries which gives rise to a new family of color codes. Interestingly, the smallest example of such a code consists of just 4 qubits and weight three parity check measurements, making it an accessible playground for today's experimentalists interested in small scale experiments on topological codes. Secondly, we catalogue the twist defects that are accessible with the color code model.

Scientific Areas:

## The quantum and private capacities of quantum channels, and the solution in the low-noise regime

Wednesday Oct 04, 2017
Speaker(s):

We first summarize background on the quantum capacity of a quantum channel, and explain why we know very little about this fundamental quantity, even for the qubit depolarizing channel (the quantum analogue of the binary symmetric channel) despite 20 years of effort by the community.

Scientific Areas:

## Towards holography via quantum source-channel codes

Wednesday Sep 20, 2017
Speaker(s):

While originally motivated by quantum computation, quantum error correction (QEC) is currently providing valuable insights into many-body quantum physics such as topological phases of matter. Furthermore, mounting evidence originating from holography research (AdS/CFT), indicates that QEC should also be pertinent for conformal field theories. With this motivation in mind, we introduce quantum source-channel codes, which combine features of lossy-compression and approximate quantum error correction, both of which are predicted in holography.

Scientific Areas:

## Alphabits, Teleportation and Black Holes

Wednesday Sep 06, 2017
Speaker(s):

The theory of alphabits is a natural generalisation of approximate quantum error correction that proves fundamental to the study of asymptotic quantum resources. In particular, it leads to an asymptotically reversible variation on quantum teleportation, called zerobit teleportation, which decomposes qubits of communication into correlation and transmission components. They also naturally arise in the study of black holes with significant consequences for the nature of quantum error correction in AdS/CFT.

## Bounding and building fault-tolerant quantum circuits on stabilizer codes

Wednesday Aug 09, 2017
Speaker(s):

Transversality is one of the most desirable features of fault-tolerant circuits because it automatically limits the propagation of errors. However, it was shown by Eastin & Knill that no universal set of quantum gates on any quantum code is transversal. In this talk, we strengthen this result for stabilizer codes to say that transversal gates must in fact be contained in the Clifford hierarchy. Moreover, we present new circuits on Bacon-Shor codes that saturate our bounds.

## Thermal stability and fault-tolerance in symmetry protected topological phases

Wednesday Jun 28, 2017
Speaker(s):

A recent breakthrough in the condensed matter community is the identification and characterization of a rich set of ordered states, known as symmetry protected topological (SPT) phases. These phases are not only fascinating from the perspective of fundamental physics but have also found powerful applications in quantum computation. Very little is known about the thermal stability of SPT ordered systems, or whether their associated computational properties may survive at non-zero temperature.

## Symmetry-protected topological phases with uniform computational power in one

Wednesday Jun 07, 2017
Speaker(s):

We investigate the usefulness of ground states of quantum spin chains with symmetry-protected topological order (SPTO) for measurement-based quantum computation. We show that, in spatial dimension one, if an SPTO phase supports quantum wire, then, subject to an additional symmetry condition that is satisfied in all cases so far investigated, it can also be used for quantum computation. Joint work with Dongsheng Wang, Abhishodh Prakash, Tzu-Chieh Wei and David Stephen; See arXiv:1609.07549v1

## Quasi-Topological Quantum Error Correction Codes

Wednesday May 31, 2017
Speaker(s):

Existing proposals for topological quantum computation have encountered

difficulties in recent years in the form of several obstructing'' results.

These are not actually no-go theorems but they do present some serious

obstacles. A further aggravation is the fact that the known topological

error correction codes only really work well in spatial dimensions higher

than three. In this talk I will present a method for modifying a higher

## Synchronous correlations, Bell inequalities, and categories of nonlocal games

Wednesday May 24, 2017
Speaker(s):

Given two sets X and Y, we consider synchronous correlations in a two-party nonlocal game with inputs X and outputs Y as a notion of generalized function between these sets (akin to a quantum graph homomorphism). We examine some structures in categories of synchronous classical, quantum, and nonsignalling strategies.

## RECENT PUBLIC LECTURE

### Erik Verlinde: A new view on gravity and the dark side of the cosmos

Speaker: Erik Verlinde