The Capabilities of a Perturbed Toric Code as a Quantum Memory

We analyze the effect of typical, unknown perturbations on the 2D toric code when acting as a quantum memory, incorporating the effects of error correction on read-out. By transforming the system into a 1D transverse Ising model undergoing an instantaneous quench, and making extensive use of Lieb-Robinson bounds, we prove that for a large class of perturbations, the survival time of stored information grows at least logarithmically with the system size. A uniform magnetic field saturates this scaling behavior. We show that randomizing the stabilizer strengths gives a polynomial survival time with a degree that depends on the strength of the perturbation.Comment: 4 and a bit pages, 3 figures v3: Published versio

Book review: what next for Labour? Ideas for a new generation by Tom Scholes-Fogg and Hisham Hamid

Tom Scholes-Fogg and Hisham Hamid present a selection of contributions from key Labour figures on what the party should do to make itself electorally viable again. While the book doesn’t add anything ground breaking to the current Labour policy debate, it clearly reiterates the fact that the Labour party as a whole is taking seriously the mistakes it made in government, and is thinking innovatively about the challenges that economic austerity presents. Reviewed by Alastair Hill

Tutorial on the Quantikz Package

This tutorial introduces (and provides, via the document source) the Quantikz LaTeX package for typesetting quantum circuit diagrams. This takes advantage of tikz to give greater control over the circuit options. Those familiar with the excellent QCircuit package will recognise much of the notation, although it has evolved a bit (hopefully simplified!).Comment: 15 pages, with many exquisite quantum circuits. Corresponding to version 0.9.6 of quantik