Automated Robot Paper Dance

It’s the paper dance, done automagically (one of the authors is a Dancing Machine, the other, not so much):

arXiv:1009.2203 [scirate arxiv]
Automated searching for quantum subsystem codes by Gregory M. Crosswhite, Dave Bacon
Quantum error correction allows for faulty quantum systems to behave in an effectively error free manner. One important class of techniques for quantum error correction is the class of quantum subsystem codes, which are relevant both to active quantum error correcting schemes as well as to the design of self-correcting quantum memories. Previous approaches for investigating these codes have focused on applying theoretical analysis to look for interesting codes and to investigate their properties. In this paper we present an alternative approach that uses computational analysis to accomplish the same goals. Specifically, we present an algorithm that computes the optimal quantum subsystem code that can be implemented given an arbitrary set of measurement operators that are tensor products of Pauli operators. We then demonstrate the utility of this algorithm by performing a systematic investigation of the quantum subsystem codes that exist in the setting where the interactions are limited to 2-body interactions between neighbors on lattices derived from the convex uniform tilings of the plane.

With pictures:

and with code to boot: http://github.com/gcross/CodeQuest/downloads.

Dead Spins And The Dirty Ground

Yep, it’s that time again. Paper dance time!

arXiv:1006.4388
Making Classical Ground State Spin Computing Fault-Tolerant
Isaac J. Crosson, Dave Bacon, Kenneth R. Brown
We examine a model of classical deterministic computing in which the ground state of the classical system is a spatial history of the computation. This model is relevant to quantum dot cellular automata as well as to recent universal adiabatic quantum computing constructions. In its most primitive form, systems constructed in this model cannot compute in an error free manner when working at non-zero temperature. However, by exploiting a mapping between the partition function for this model and probabilistic classical circuits we are able to show that it is possible to make this model effectively error free. We achieve this by using techniques in fault-tolerant classical computing and the result is that the system can compute effectively error free if the temperature is below a critical temperature. We further link this model to computational complexity and show that a certain problem concerning finite temperature classical spin systems is complete for the complexity class Merlin-Arthur. This provides an interesting connection between the physical behavior of certain many-body spin systems and computational complexity.

We Belong Together, Adiabatically

A paper dance today! Yes, indeed, it’s another slow dance (scirate, arXiv:0912.2098):

Adiabatic Cluster State Quantum Computing
Authors: Dave Bacon, Steven T. Flammia
Abstract: Models of quantum computation are important because they change the physical requirements for achieving universal quantum computation (QC). For example, one-way QC requires the preparation of an entangled “cluster” state followed by adaptive measurement on this state, a set of requirements which is different from the standard quantum circuit model. Here we introduce a model based on one-way QC but without measurements (except for the final readout), instead using adiabatic deformation of a Hamiltonian whose initial ground state is the cluster state. This opens the possibility to use the copious results from one-way QC to build more feasible adiabatic schemes.

Count the Headlights on the Highway

Yep, it’s paper dance time. This one is less of a dance and more of a shuffle:

arXiv:0808.0174 (scirate)
Title: Simon’s Algorithm, Clebsch-Gordan Sieves, and Hidden Symmetries of Multiple Squares
Author: D. Bacon
Abstract: The first quantum algorithm to offer an exponential speedup (in the query complexity setting) over classical algorithms was Simon’s algorithm for identifying a hidden exclusive-or mask. Here we observe how part of Simon’s algorithm can be interpreted as a Clebsch-Gordan transform. Inspired by this we show how Clebsch-Gordan transforms can be used to efficiently find a hidden involution on the group G^n where G is the dihedral group of order eight (the group of symmetries of a square.) This problem previously admitted an efficient quantum algorithm but a connection to Clebsch-Gordan transforms had not been made. Our results provide further evidence for the usefulness of Clebsch-Gordan transform in quantum algorithm design.

Yet another step in my ever increasing quest to become a lone author lunatic (er, lunatic!) of quant-ph. Next step is obviously Microsoft Word only arXiv postings.
Bonus points for identifying the song, of course.