Past Quantum Field Theory Seminar

30 October 2012
Alastair Kay

Topological quantum error correcting codes, such as the Toric code, are
ideal candidates for protecting a logical quantum bit against local noise.
How are we to get the best performance from these codes when an unknown
local perturbation is applied? This talk will discuss how knowledge, or lack
thereof, about the error affects the error correcting threshold, and how
thresholds can be improved by introducing randomness to the system. These
studies are directed at trying to understand how quantum information can be
encoded and passively protected in order to maximise the span of time between successive rounds of error correction, and what properties are
required of a topological system to induce a survival time that grows
sufficiently rapidly with system size. The talk is based on the following
papers: arXiv:1208.4924 and Phys. Rev. Lett. 107, 270502 (2011).

  • Quantum Field Theory Seminar
15 May 2012
Elizabeth Gasparim (UNICAMP-Brazil)
This is a report of joint work with T. Koppe, P. Majumdar, and K.  Ray. I will define new partition functions for theories with targets on toric singularities via products of old partition functions on  crepant resolutions. I will present explicit examples  and show that the  new partition functions turn out to be homogeneous on MacMahon factors.
  • Quantum Field Theory Seminar
31 January 2012
Malcolm Fairbairn (KCL)
We still don't know what dark matter is but a class of leading candidates are weakly interacting massive particles or WIMPs. These WIMP models are falsifiable, which is why we like them. However, the epoch of their falsifiability is upon us and a slew of data from different directions is placing models for WIMPs under pressure. I will try and present an updated overview of the different pieces of evidence, false (?) alarms and controversies that are making this such an active area of research at the moment.
  • Quantum Field Theory Seminar