Can Classical Noise Enhance Quantum Transmission?

A modified quantum teleportation protocol broadens the scope of the classical forbidden-interval theorems for stochastic resonance. The fidelity measures performance of quantum communication. The sender encodes the two classical bits for quantum teleportation as weak bipolar subthreshold signals and sends them over a noisy classical channel. Two forbidden-interval theorems provide a necessary and sufficient condition for the occurrence of the nonmonotone stochastic resonance effect in the fidelity of quantum teleportation. The condition is that the noise mean must fall outside a forbidden interval related to the detection threshold and signal value. An optimal amount of classical noise benefits quantum communication when the sender transmits weak signals, the receiver detects with a high threshold, and the noise mean lies outside the forbidden interval. Theorems and simulations demonstrate that both finite-variance and infinite-variance noise benefit the fidelity of quantum teleportation.Comment: 11 pages, 3 figures, replaced with published version that includes new section on imperfect entanglement and references to J. J. Ting's earlier wor

A Monthly Cycle in Food Expenditure and Intake by Participants in the U.S. Food Stamp Program

This paper uses nationally representative data to describe monthly cycles in food expenditure and food intake by food stamp recipients. Food expenditure peaks sharply in the first 3 days after food stamps are received. The corresponding cycle in food intake differs for various categories of food stamp recipients. Food stamp recipients who also receive AFDC appear to maintain steady food intake across the whole month, while AFDC nonrecipients experience a significant drop in intake at the end of the month. Children appear to maintain steady food intake, while adults appear to experience a significant drop. Households that conduct major grocery shopping trips more frequently than once per month maintain steady food intake, while households that shop less frequently experience a significant drop. The food stamp cycle has implications for two areas of research: the measurement of hunger and food insecurity in the United States and the measurement of the impact of the U.S. Food Stamp Program. Intramonthly patterns in food expenditure and food intake have potential implications for policy decisions about the frequency of food stamp benefit delivery, the evaluation of new electronic benefit transfer systems that are replacing traditional food stamp coupons, and nutrition education efforts.

p-topological and p-regular: dual notions in convergence theory

The natural duality between "topological" and "regular," both considered as convergence space properties, extends naturally to p-regular convergence spaces, resulting in the new concept of a p-topological convergence space. Taking advantage of this duality, the behavior of p-topological and p-regular convergence spaces is explored, with particular emphasis on the former, since they have not been previously studied. Their study leads to the new notion of a neighborhood operator for filters, which in turn leads to an especially simple characterization of a topology in terms of convergence criteria. Applications include the topological and regularity series of a convergence space.Comment: 12 pages in Acrobat 3.0 PDF forma

An assessment of the potential returns of energy certificates for the UK household sector

Purpose – This article seeks to investigate the interconnections between the expectations of the impact of energy certificates issued within the UK domestic building sector through the Energy Performance of Buildings Directive (EPBD) and the actual number and financial implications of the energy saving measures (ESMs) achieved. Design/methodology/approach – The methodology uses two previously published surveys and compares these with a third independent survey by the authors focusing upon the discrepancies between planned action and implemented action, introducing the term human factor element (hfe). Findings – The article concludes that annual carbon savings arising from implementation of the Energy Performance Certificate (EPC) may be as low as 73.4?ktC over the five year term of the Kyoto Protocol even though 44 per cent of energy saving measure costs of £200 million are recouped within the same time period and savings will continue for up to 40 years. Achieving annual savings of only 14.7?ktC by 2010, such a figure represents a mere 0.3 per cent of the annual domestic 4.8?MtC savings announced by the government in its 2006 Climate Change Programme. Practical implications – Since the principal determinant in the uptake of ESMs is initial cost, it is considered that the EPBD is likely to remain an under-performing instrument in the promotion of energy sufficiency until such time as other complementary provisions are introduced. Originality/value – Sheds light upon the likely financial impact upon energy efficiency in domestic buildings by energy certificates

Stochastic resonance in Gaussian quantum channels

We determine conditions for the presence of stochastic resonance in a lossy bosonic channel with a nonlinear, threshold decoding. The stochastic resonance effect occurs if and only if the detection threshold is outside of a "forbidden interval". We show that it takes place in different settings: when transmitting classical messages through a lossy bosonic channel, when transmitting over an entanglement-assisted lossy bosonic channel, and when discriminating channels with different loss parameters. Moreover, we consider a setting in which stochastic resonance occurs in the transmission of a qubit over a lossy bosonic channel with a particular encoding and decoding. In all cases, we assume the addition of Gaussian noise to the signal and show that it does not matter who, between sender and receiver, introduces such a noise. Remarkably, different results are obtained when considering a setting for private communication. In this case the symmetry between sender and receiver is broken and the "forbidden interval" may vanish, leading to the occurrence of stochastic resonance effects for any value of the detection threshold.Comment: 17 pages, 6 figures. Manuscript improved in many ways. New results on private communication adde

Joint source-channel coding for a quantum multiple access channel

Suppose that two senders each obtain one share of the output of a classical, bivariate, correlated information source. They would like to transmit the correlated source to a receiver using a quantum multiple access channel. In prior work, Cover, El Gamal, and Salehi provided a combined source-channel coding strategy for a classical multiple access channel which outperforms the simpler "separation" strategy where separate codebooks are used for the source coding and the channel coding tasks. In the present paper, we prove that a coding strategy similar to the Cover-El Gamal-Salehi strategy and a corresponding quantum simultaneous decoder allow for the reliable transmission of a source over a quantum multiple access channel, as long as a set of information inequalities involving the Holevo quantity hold.Comment: 21 pages, v2: minor changes, accepted into Journal of Physics

Entanglement-Assisted Quantum Error Correction with Linear Optics

We construct a theory of continuous-variable entanglement-assisted quantum error correction. We present an example of a continuous-variable entanglement-assisted code that corrects for an arbitrary single-mode error. We also show how to implement encoding circuits using passive optical devices, homodyne measurements, feedforward classical communication, conditional displacements, and off-line squeezers.Comment: 8 pages, 1 figure, major expansion of paper with detailed exampl

Long-distance sound propagation over discontinuous impedances

A calculation method is presented for sound propagation over an impedance discontinuity in flat ground with a homogeneous, still atmosphere. The method is based on an approximate solution to a two dimensional boundary integral equation formulation of the problem, which expresses the wave field as the solution for homogeneous ground plus an integral over half of the boundary. Through recognizing this integral as a generalized Fourier integral, asymptotic methods are applied to evaluate the part of the integral most expensive to compute by numerical quadrature. Single frequency excess attenuation results for propagation from a point source above rigid ground to a receiver above absorbing ground are discussed. The results are applied, with air attenuation and A-weighting, to a notional jet engine noise source. Simple trends are noted