[quantum-info] Today's PIQuDos

Markus Müller markus14m at gmail.com
Wed Mar 7 10:04:37 EST 2012


A reminder of Jeongwan Haah's talk at 4pm in the Time room at PI.



Title: *Demonstration of self-correcting quantum memory in three dimensions*
Speaker: Jeongwan Haah (IQI Caltech)

Abstract:
Based on the joint work with Sergey Bravyi, IBM Watson.

We show that any topologically ordered local stabilizer model of spins
in three dimensional lattices that lacks string logical operators can
be used as a reliable quantum memory against thermal noise. It is
shown that any local process creating a topologically charged particle
separated from other particles by distance $R$, must cross an energy
barrier of height $c \log R$. This property makes the model glassy. We
devise an efficient decoding algorithm that should be used at the
final read-out, and prove a lower bound on the memory time until which
the fidelity between the outcome of the decoder and the initial state
is close to 1. The memory time increases as $L^{\beta}$ where $L$ is
the system size and $\beta$ the inverse temperature, as long as $L<
L^\star \sim e^\beta$. Hence, the optimal memory time scales as
$e^{\beta^2}$. Our bound applies when the system interacts with
thermal bath via a Markovian master equation. We give an example of 3D
local stabilizer codes that satisfies all of our assumptions. We
numerically verify for this example that our bound is tight up to
constants.

Date: March 07, 2012 - 4:00 pm
Series: Perimeter Institute Quantum Discussions
Location: Time Rm
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