Andrew S. Fletcher

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Quantum error correction ͑QEC͒ is an essential element of physical quantum information processing systems. Most QEC efforts focus on extending classical error correction schemes to the quantum regime. The input to a noisy system is embedded in a coded subspace, and error recovery is performed via an operation designed to perfectly correct for a set of(More)
Quantum error correction (QEC) is an essential concept for any quantum information processing device. Typically, QEC is designed with minimal assumptions about the noise process; this generic assumption exacts a high cost in efficiency and performance. We examine QEC methods that are adapted to the physical noise model. In physical systems, errors are not(More)
recommendations are those of the author and are not necessarily endorsed by the United States Government. ABSTRACT To achieve high signal-to-noise ratios (SNR) while maintaining moderate sensor size, an architecture is proposed to combine several independent radar apertures into a coherently functioning unit. The proposed system utilizes several distinct(More)
— We consider error correction procedures designed specifically for the amplitude damping channel. We analyze amplitude damping errors in the stabilizer formalism. This analysis allows a generalization of the [4, 1] 'approximate' amplitude damping code of [1]. We present this generalization as a class of [2(M + 1), M ] codes for M ≥ 1 and present quantum(More)
We present a class of numerical algorithms which adapt a quantum error correction scheme to a channel model. Given an encoding and a channel model, it was previously shown that the quantum operation that maximizes the average entanglement fidelity may be calculated by a semidefinite program ͑SDP͒, which is a convex optimization. While optimal, this recovery(More)
BACKGROUND The PneuX System is a novel endotracheal tube and tracheal seal monitor, which has been designed to minimise the aspiration of oropharyngeal secretions. We aimed to determine the incidence of ventilator-associated pneumonia (VAP) in patients who were intubated with the PneuX System and to establish whether intermittent subglottic secretion(More)
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