Study of contamination of liquid oxygen by gaseous nitrogen First quarterly report, 1 Jul. - 30 Sep. 1964

Analytical model development for contamination study of liquid oxygen by gaseous nitroge

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

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

Smanjenje studija fizike

This paper draws attention to the diminishing number of students studying physics both at schools and universities despite its enormous importance for a modern technological society. One possible reason is that many teachers do not convey fully the fascination and excitement of physics and hence fail to inspire young people. A possible way of overcoming this is to place emphasis on "hands-on\u27\u27 experimental work which can be carried out using simple and inexpensive materials which are readily available. Examples of this are given.Upozoravamo na smanjenje broja slušača fizike u školama i na sveučilištima usprkos ogromne važnosti fizike za suvremeno tehnološko društvo. Možda je razlog što nastavnici ne prenose čar i uzbuđenje fizičkih otkrića i propuštaju oduševiti mlade ljude. Moguć način za prevladavanje stanja je da se stavi naglasak na osobni eksperimentalni rad koji se može izvoditi jednostavnim i jeftinim pomagalima, i koja su lako dostupna. Daju se primjeri

Exploring the effectiveness of media in communicating public health messages to people with learning disabilities during the pandemic

The article aims to explore mass and social media’s role in communicating public health messages in Britain during the COVID-19 pandemic. The article presents findings from a realist mixed methods study analysing data collected from 137 participants who have a learning disability and/or autism. Our study discovered that participants reported that social media only led to confusion because of contradictory messages being presented on COVID-19. Although people with learning disabilities and/or autism preferred gaining information from TV news, they also reported that this information was often confusing and inaccessible. Participants drew on family members, and social care professionals, to explain and help them negotiate the complexities of public health messages during the global pandemic. The study concludes by suggesting the need for accessible information and health communications to effectively contend with any future global pandemic or health emergency to reduce the health risks for people with learning disabilities and/or autism

Entanglement-Assisted Quantum Error-Correcting Codes with Imperfect Ebits

The scheme of entanglement-assisted quantum error-correcting (EAQEC) codes assumes that the ebits of the receiver are error-free. In practical situations, errors on these ebits are unavoidable, which diminishes the error-correcting ability of these codes. We consider two different versions of this problem. We first show that any (nondegenerate) standard stabilizer code can be transformed into an EAQEC code that can correct errors on the qubits of both sender and receiver. These EAQEC codes are equivalent to standard stabilizer codes, and hence the decoding techniques of standard stabilizer codes can be applied. Several EAQEC codes of this type are found to be optimal. In a second scheme, the receiver uses a standard stabilizer code to protect the ebits, which we call a "combination code." The performances of different quantum codes are compared in terms of the channel fidelity over the depolarizing channel. We give a formula for the channel fidelity over the depolarizing channel (or any Pauli error channel), and show that it can be efficiently approximated by a Monte Carlo calculation. Finally, we discuss the tradeoff between performing extra entanglement distillation and applying an EAQEC code with imperfect ebits.Comment: 15 pages, 12 figure

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

A Feynman-Kac Formula for Anticommuting Brownian Motion

Motivated by application to quantum physics, anticommuting analogues of Wiener measure and Brownian motion are constructed. The corresponding Ito integrals are defined and the existence and uniqueness of solutions to a class of stochastic differential equations is established. This machinery is used to provide a Feynman-Kac formula for a class of Hamiltonians. Several specific examples are considered.Comment: 21 page

Improving the quality management systems for energy-efficient social housing projects

Developing and implementing quality management systems (QMS) in construction is particularly difficult because of a lack of standardization, the use of transient workforce and the many parties involved. This paper discusses the challenges faced by social housing providers in the UK when implementing quality assurance programs in their effort to provide their tenants with energy-efficient dwellings. In particular, it focuses on the quality plans defined at the early stages of a project, their impact during the construction process and on the resulting building energy performance. Based on data collected from the project team and documentation, a comparative analysis of the QMS development process of two social housing developments is presented. The key findings show that the two case studies followed different quality management approaches to deliver energy efficient dwellings. The most significant discrepancies were found in defining the energy performance targets and detailing the quality assurance procedures. The contribution of this paper is to create awareness of the importance of defining Quality Assurance Systems with a focus on energy performance from the early stages of a project