A Unified and Generalized Approach to Quantum Error Correction

We present a unified approach to quantum error correction, called operator quantum error correction. This scheme relies on a generalized notion of noiseless subsystems that is not restricted to the commutant of the interaction algebra. We arrive at the unified approach, which incorporates the known techniques -- i.e. the standard error correction model, the method of decoherence-free subspaces, and the noiseless subsystem method -- as special cases, by combining active error correction with this generalized noiseless subsystem method. Moreover, we demonstrate that the quantum error correction condition from the standard model is a necessary condition for all known methods of quantum error correction.Comment: 5 page

Analysis of New Hampshire Pregnancy Risk Assessment Monitoring System (PRAMS) to Better Understand Breastfeeding Initiation and Duration by Industry Category

This supplemental report provides additional information on breastfeeding initiation and duration, and a woman’s job category (industry) as reported to the NH Division of Vital Records Administration via the NH birth certificate. De-identified responses in the NH birth certificate data linked to the responses in the Pregnancy Risk Assessment Monitoring System (PRAMS) survey data provided the opportunity to better understand duration of breastfeeding by a woman’s industry. The findings may be useful to policymakers and employers when framed in terms of the health and economic benefits of breastfeeding to inform workplace policy formation

Exponential speed-up with a single bit of quantum information: Testing the quantum butterfly effect

We present an efficient quantum algorithm to measure the average fidelity decay of a quantum map under perturbation using a single bit of quantum information. Our algorithm scales only as the complexity of the map under investigation, so for those maps admitting an efficient gate decomposition, it provides an exponential speed up over known classical procedures. Fidelity decay is important in the study of complex dynamical systems, where it is conjectured to be a signature of quantum chaos. Our result also illustrates the role of chaos in the process of decoherence.Comment: 4 pages, 2 eps figure

Smart Concrete for Enhanced Nondestructive Evaluation

The authors recently investigated the use of conductive concrete to enhance nondestructive evaluation (NDE) capa- bilities. Preliminary results have shown that a conductive concrete can facilitate the utilization of an eddy current technique, where damages in a conductive specimen were easier to detect compared with a non-conductive substrate. While such results demonstrated the promise of using conductive concrete to facilitate and potentially accelerate the NDE process, the fabrication of an homogeneous conductive concrete is technically or economically challenging, depending on the conductive filler used in the process. In this paper, we propose a new cementitious composite to accelerate NDE. The composite uses inexpensive carbon black particles (CB) and a block-copolymer. The purpose of the block co-polymer, a styrene-ethylene-butylene-styrene (SEBS), is to facilitate the creation of conductive chains, therefore reducing the necessary concentration of conductive filler required to achieve electrical percolation. Several cementitious composite specimens of various concentrations of CB are fabricated, and results show that the utilization of SEBS reduces the electrical percolation threshold by approximately 50% with a gain on electrical conductivity relative to a non-conductive specimen mix of approximately 33%. Strain-sensing tests also demonstrate that SEBS-based specimens have good sensing properties, but lag behind those of conductive concrete specimens fabricated with CB only

Statistical comparison of ensemble implementations of Grover's search algorithm to classical sequential searches

We compare pseudopure state ensemble implementations, quantified by their initial polarization and ensemble size, of Grover's search algorithm to probabilistic classical sequential search algorithms in terms of their success and failure probabilities. We propose a criterion for quantifying the resources used by the ensemble implementation via the aggregate number of oracle invocations across the entire ensemble and use this as a basis for comparison with classical search algorithms. We determine bounds for a critical polarization such that the ensemble algorithm succeeds with a greater probability than the probabilistic classical sequential search. Our results indicate that the critical polarization scales as N^(-1/4) where N is the database size and that for typical room temperature solution state NMR, the polarization is such that the ensemble implementation of Grover's algorithm would be advantageous for N > 10^2