Quantum Networks for Concentrating Entanglement

If two parties, Alice and Bob, share some number, n, of partially entangled pairs of qubits, then it is possible for them to concentrate these pairs into some smaller number of maximally entangled states. We present a simplified version of the algorithm for such entanglement concentration, and we describe efficient networks for implementing these operations.Comment: 15 pages, 2 figure

Techniques for Quantum Computing

This thesis is about techniques for quantum computing. A common theme throughout this work is the examination of how quantum algorithms and protocols might be implemented in practice. I explore this question at the level of algorithmic details and computer architecture, and not at the level of specific physical systems for performing quantum computation. The first problem I consider is the generation of quantum states. Many results in quantum information theory require the generation of specific quantum states, such as Bell states. Some states can be efficiently created using standard quantum computational primitives such as preparing a qubit in the state |0> and applying a sequence of quantum gates (from a finite set). For example, a Bell state can be prepared from the state |00> using a Hadamard gate and a controlled-NOT gate. However, many states cannot be efficiently created. Chapter 1 of this thesis focusses on the generation of quantum states. In Chapter 2, I explore implementations of Shor's quantum algorithm for computing discrete logarithms. This algorithm is particularly significant because it threatens to undermine the security of widely used elliptic curve cryptosystems. I give a strategy for implementing Shor's algorithm for finding discrete logarithms in groups of points on elliptic curves over fields of characteristic 2. Chapter 3 is about globally controlled arrays, which is a paradigm for implementing quantum computers that may prove to be more feasible in practice than the quantum circuit model. I explore strategies for implementing error correction in such global control models, so that they might be implemented more robustly. I also cast the various global control schemes that have appeared in the literature into a unified framework so that their properties can be studied somewhat independently of the differences in low-level details. Using this framework, I consider the main challenges and obstacles to implementing quantum computing fault tolerantly using globally controlled arrays. Finally, in Chapter 4, I consider algorithmic cooling---a technique that is potentially important for making quantum computation using nuclear magnetic resonance (NMR) feasible. Given the constraints imposed by the NMR approach to quantum computing, the most likely cooling algorithms to be practicable are those based on simple reversible polarization (RPC) operations acting locally on small numbers of bits. Algorithms using 2- and 3-bit RPC operations have appeared in the literature, and these are the algorithms I consider in Chapter 4. Specifically, I show that the RPC operation used in all these algorithms is essentially a majority-vote of 3 bits, and prove the optimality of the best such algorithm (in a restricted setting). I go on to derive some theoretical bounds on the performance of these algorithms under some specific assumptions about errors. These bounds are independent of implementation details and low-level algorithmic details

Spectroscopy of Early F Stars: γ Doradus Candidates and Possible Metallic Shell Stars

We obtained high-resolution spectroscopic observations of 34 γ Doradus candidates. From the red-wavelength spectra, we determined spectral classes, radial velocities, and projected rotational velocities. The spectra of seven late A or early F stars show metallic lines that have composite profiles consisting of a narrow component near the center of a broad line, indicating that they may be shell stars or binaries. Several stars, including HD 152896, HD 173977, HD 175337, and HD 195068/9, show large line profile asymmetries. Two stars, HD 11443 (=α Trianguli) and HD 149420, are ellipsoidal variables and not γ Doradus stars. The percentage of binary systems in our sample may be as high as 74%

Investigation of Salmonella Contamination of Pigs in Australia

Microbiological surveys of pigs before, during and after slaughter and processing have been conducted at abattoirs in Australia, to estimate the incidence and risk factors for Salmonella contamination on carcasses. In one such survey, approximately 10% of carcasses were positive for Salmonella contamination at the end of the slaughter line, although there was considerable variation between abattoirs and between herds in the incidence of contamination. A range of Salmonella serotypes was recovered from carcasses, with the most common being S. derby, S. give, S. anatum, and S. ohio. The incidence of Salmonella contamination on carcasses varied along the slaughter line: some contamination on the skin surface of carcasses survived scalding and dehairing, despite the temperatures achieved during these processes

The prevalence of, and factors associated with, paying for sex among men resident in Britain: findings from the third National Survey of Sexual Attitudes and Lifestyles (Natsal-3).

OBJECTIVES: Men who pay for sex (MPS) are considered a bridging population for sexually transmitted infections (STI). However, the extent, characteristics and role of MPS in transmission is poorly understood. We investigate these questions using data from Britain's third National Survey of Sexual Attitudes and Lifestyles (Natsal-3). METHODS: We performed complex survey analyses of data from 6293 men aged 16-74 years resident in Britain who completed Natsal-3, a probability sample survey undertaken during 2010-2012, using computer-assisted personal interviewing and computer-assisted self-interview. RESULTS: 11.0% (95% CI10.1% to 11.9%) of all men reported ever paying for sex. Among MPS, 18.4% (95% CI 18.2% to 18.7%) of their lifetime sexual partners were paid. 3.6% (95% CI 3.1% to 4.2%) of men had paid for sex in the past 5 years. Partners of MPS constitute 14.7% of all reported partners and MPS report 15.6% of all reported STI diagnoses in the past 5 years. Paying for sex in the past 5 years was strongly associated with reporting larger numbers of sexual partners (adjusted OR, AOR for 5+ partners, past 5 years, 31.50, 95% CI 18.69 to 53.09). After adjusting for partner numbers, paying for sex remained strongly associated with reporting new foreign partners outside the UK (AOR 7.96; 95% CI 4.97 to 12.73) and STI diagnosis/es (AOR 2.34; 95% CI 1.44 to 3.81), all in the past 5 years. Among men ever paying for sex, 62.6% (95% CI 58.3% to 66.8%) reported paying for sex outside the UK, most often in Europe and Asia. CONCLUSIONS: MPS in Britain remain at greater risk of STI acquisition and onward transmission than men who do not. They report high numbers of partners, but the minority are paid partners. They are an important core group in STI transmission

Endoscopic management of Barrett’s dysplasia and early neoplasia: efficacy, safety and long-term outcomes in a UK tertiary centre

Background and Objectives: Endoscopic mucosal resection (EMR) and radiofrequency ablation (RFA) are effective treatments for dysplastic Barrett’s esophagus (BE). This study evaluates efficacy, durability and safety in a single high-volume UK tertiary centre with 15-years’ experience.Methods: Prospective data from Nottingham University Hospitals 2004-2019 for endotherapy of dysplastic BE or intramucosal adenocarcinoma. Procedural outcome measures: complete resection, complications and surgery rates. Efficacy outcomes: complete remission of dysplasia (CR-D) and intestinal metaplasia (CR-IM), recurrence, treatment failure rates, durability of RFA, median follow up and tumour associated mortality. Results: 319 lesions were resected. 671 RFAs were performed on 239 patients. Median age was 67(±9.5) years, male:female ratio was 5:1 and median BE length was C3(IQR:6) M6(IQR:5). The most common lesion was Paris IIa(64%) with a median size of 10mm(3-70). Final histology was adenocarcinoma in 50%. Complete resection rates were 96%. The multiband mucosectomy technique (91%) was most commonly used. The median number of RFA sessions was 3(IQR:2). The rates of CR-D and CR-IM were 90.4%% and 89.8% achieved after a median of 20.1(IQR:14) months. The most common complications: EMR was bleeding 2.2% and RFA was stricture (5.4%) requiring a median of 2 (range 1-7) dilatations. Median follow up post CR-IM/CR-D was 38 months(14-60). Metachronous lesions developed in 4.7% after CR-D and tumour related mortality was 0.8%. Dysplasia and intestinal metaplasia free survival at 5 years was 95% and 90% respectively. Conclusions: BE endotherapy is minimally invasive, effective, safe and deliverable in a day-case settin

The Zwicky Transient Facility: Observing System

The Zwicky Transient Facility (ZTF) Observing System (OS) is the data collector for the ZTF project to study astrophysical phenomena in the time domain. ZTF OS is based upon the 48 inch aperture Schmidt-type design Samuel Oschin Telescope at the Palomar Observatory in Southern California. It incorporates new telescope aspheric corrector optics, dome and telescope drives, a large-format exposure shutter, a flat-field illumination system, a robotic bandpass filter exchanger, and the key element: a new 47-square-degree, 600 megapixel cryogenic CCD mosaic science camera, along with supporting equipment. The OS collects and delivers digitized survey data to the ZTF Data System (DS). Here, we describe the ZTF OS design, optical implementation, delivered image quality, detector performance, and robotic survey efficiency